Student CPU

Difference Server Type Hardware Configuration Data Center

2012-01-09T03:10:00.000-08:00

RACK Server:
1) Rack server is typically measured by U’s scale in vertically.
Like 1U, 2U, 3U.
BLADE Server:
Blade server an additional level innovation of RACK Server.
It has two parts.
a) Blade carrier
b) Blade Server
Blade server typically placed inside the Blade Carrier by together they form blade system.

Advantages
Hot Plugging like, Network ports, Power Connection, Switches are modular design.
There is no need to plug manually. Just we have to insert the blade server into blade carrier.

How To Configure RSH – Remote Shell

2012-01-09T00:21:00.000-08:00

1) Enable rsh
#vim /etc/xinetd.d/rsh
Replace
disable=yes into disable=no
wait = yes into wait=no
2) Enable rexec
#vim /etc/xinetd.d/rexec
Replace
disable=yes into disable=no
wait=yes into disable=no
3)Enable rlogin
#vim /etc/xinetd.d/rlogin
disable=yes into disable=no
wait=yes into wait=no
4) Enable securetty
Add rsh,rlogin.rexec into the /etc/securetty
/etc/securetty
Enable the service for login with tty devices.
5) PAM - Pluggable Authentication Module.
Purpose
1) Authentication condition.
2) Define the Session Module.
#vim /etc/pam.d/rsh
Replace
auth required pam_rhosts.so into
auth sufficient pam_rhosts.so

6) Add the trusted Host List
#vim /root/.rhosts
List of hosts Login without password or server admin granted "TRUSTED"
rsh/rlogin Remote access without supplying Password.

Finally trying from the Client Machine, using rsh,rlogin,to verify rsh- Remote shell.

Compare Time stamp In Shell Script year, Month day, Hour, Minute, Second

2012-01-09T00:12:00.000-08:00

Linux How To Compare the timestamp
1) Using Date command we can compare
2) In these format i used just simple numberical comparsion and it'wll work for timestamp comparsion.
Year-Month-day-Hour-Minute-second.
3)syntax
Date1=`date +%Y%m%d%H%m%S`;
Date2=`date +%Y%m%d%H%m%S`;
if(Date1 Condition Date2)
date +
%y - Year in Two Digit
%Y - year in Four Digit
%m - month in Numberic
%d - Date
%H- Hours
%h - Month in String

For Example
current_time=`date +%Y%m%d%H%M%S`;
Year-Month-Date-Hour- Minute-Second
if [ "$login_time" -lt "$current_time" ]; then
How To Compare Time stamp in Shell Script.

How To Create initrd Image Temporary File System initrd

2011-12-27T08:37:00.000-08:00

1)initrd is a image file.
2)initialize Ram Disk Image.
3)initrd is temporary file system used in the boot Process of the Linux Kernel.
4)initrd contain basic executable files utilities and Essential Drivers, that leads kernel to mount root File system.
5)In these temporary file system it contain directory, bin,etc,init,dev,lib,loopfs,proc,sys,sysroot File is init.
6)This initrd image Contain the Same version & Number of kernel
Example
initrd Image initrd-2.6.9-5.EL.img
kernel vmlinuz-2.6.9-5.EL

How To Extract Initrd File.
#gunzip < /boot/initrd.img | cpio -i
cpio -i It will Extract the Image.
-o Create the Image
-v Verbose.
1) Copying files from Archive
2) Extracting Files from Archive
#ls /etc/*.conf | cpio -o --forma=tar > conf.tar

Difference Between Incremental Backup Differential Backup Rotational Backup

2011-11-14T09:38:00.000-08:00

Incremental Backup: Backup of files that's are NEW or CHANGED Since Last Backup.
Backup Time: It will take the least time.

Differential Backup: Backup of the files, which are NEW or CHANGED Since LAST FULL Backup.
Backup Time : It will take more time compare to Incremental Backup.

Comparison : Incremental Vs Differential
Differential Backup it is middle stage between Full Backup & Differential Backup.
Main Difference is Incremental take backup from Last Backup. Differential take backup from LAST FULL Backup,

FULL BACKUP: Complete Backup of everything.
Backup Time: It will take more time rather than DIFFERENTIAL BAKUP.

Compile Kernel Install Remove Kernel Driver Module

2011-11-10T10:39:00.000-08:00

Purpose- Reason For Kernel Compilation
Advantages
1) It is easy to Add New Features.
2) For new Hardware if it does not have proper
kernel Module, then we can rebuilt the kernel through Kernel compilation.

How To Compile Linux Kernel Source code.
1) Go to the Linux Kernel Directory/usr/src/kernels/2.6.9-5.EL-i686
Type #make menuconfig
2) Configure & compile the Kernel Source Code
For Example To Add Driver for Key board Choose the Following Sub Menu from the #make menuconfig.
-make menuconfig - Device Drivers - Input Device Support - Keyboard - Choose the Keyboard,
3)#make menuconfig. It will build their Kernel Driver Modules Under /lib/module/`uname –r`

Linux Kernel Important Directories
1)/lib/modules/`uname -r` - Kernel Driver Modules
/lib/modules/2.6.9-5.EL/kernel/drivers/ - Contain the Linux Kernel Driver.
2) /usr/src/kernels/2.6.18-128.el5/ Contain the Linux Kernel Source.
3)/usr/include/linux - It contain the List of Header Files
/lib/modules/2.6.9-5.EL/kernel/drivers/net/ - Network Driver Modules
/lib/modules/2.6.9-5.EL/kernel/drivers/input – Keyboard, Mouse Driver Modules

How To Find Module Dependencies List Modules
lsmod List Modules Get the Information From the /proc/modules.
depmod list the dependencies module.
depmod -v List Which module is depend on the other module.
For Example: via-velocity.ko it is Network Module located Under /lib/modules/version/kernel/drivers/net/filename.ko
/lib/modules/2.6.9-5.EL/kernel/drivers/net/via-velocity.ko needs "crc_ccitt": /lib/modules/2.6.9-5.EL/kernel/lib/crc-ccitt.ko
.ko it is kernel Modules

How To Install Or Remove The Module Loading / Unloading Module
modprobe - Install/remove the Module
insmod - Insert The Module
rmmod - Remove The Module
Compression Between modprobe And insmod/rmmod
1) For modprobe there is no need to mention any path. It is automatically install the module. But Insmod , rmmod we have to mention the Path.
Example:
#insmod kernel/drivers/net/wireless/airo.ko
2) Using Single Command we will Install & Remove Module for modprobe. We had separate command like insmod , rmmod.

/usr/bin/ld Cannot Find Library Path Linkage Problem

2011-11-10T07:34:00.000-08:00

STUDY : Open Source Application MakeFile Important Environment Variable.
CFLAGS - C Compiler Flags.
LDFLAGS - Library Path
CC C - Compiler Command.
-L - User Define Library path Example -L /usr/X11R6/lib/.
-l - Search from Common Library Path(/lib) -lX11.
#gcc -L /folder/contain/library/path/event/ -levent.

When I try to install Open Source Application I got the Following ERROR MESSAGE:
/usr/bin/ld: cannot find -lX11
collect2: ld returned 1 exit status
make: *** [eterm] Error 1

REASON : This type of issue Happened when it does not find the Proper Libraries in the Default Path(lib) or (-L) Specified Location.

FULL ERROR MESSAGE : cc -o eterm main.o init.o close.o font.o gc.o api.o sink.o select.o serial.o print.o tot_compose.o -O2 -Wall -fomit-frame-pointer -march=i386 -s -L /usr/X11/lib libansi.a libvt.a libsie.a libtel.a libwy.a -lX11 -L ../../OPT/MLT-Display-Lib/ -liscdisp -lstdc++ -L ../../opt/getval -lgetval
/usr/bin/ld: cannot find -lX11
collect2: ld returned 1 exit status
make: *** [eterm] Error 1

SOLUTION:
1) We have to install the Proper Library Package.
2) Or if it is already installed, we need to Link the Correct Library Path with -L and -l Option.

....-march=i386 -s -L /usr/X11/lib .... libtel.a libwy.a -lX11

From the Above Statement it tries to find the Library X11 from /usr/X11/lib.
But it can't find, Because X11 Located in /usr/X11R6/lib/.
So we have to replace from /usr/X11/lib to /usr/X11R6/lib. Change this Variable (LDFLAGS) in Makefile.

How To Find Out,Whether Library Package Is Already Install Or Not.
METHOD 1
#gcc program.c -lgetval
1)-lgetval is Library.
2) It is located under Default Library Path /lib
3) To find #locate getval | grep lib
File is located under /lib/libgetval.so
METHOD 2
#gcc graphics.h -L /usr/X11/lib –lX11
1) We have to Search Xll library path under /usr/X11/lib
2) #find /usr/X11/lib –name X11*
3) If it is not located, we have to search whether is it located in any another Path. Like
4)#find / -name X11*
5)if it is locate then change –L Correct Directory Path or
6)if it can't find anywhere else, Then we have to install particular library.

Similar Error Message:
/usr/bin/ld: cannot find -lz

/usr/bin/ld: cannot find -lc

/usr/bin/ld: cannot find -lgcc_s_32

/usr/bin/ld: cannot find -lXaw

/usr/bin/ld: cannot find -lImlib2

/usr/bin/ld: cannot find -lperl

Sed Command Search Replace Delete Add Line Tricks and Tips

2011-11-08T10:24:00.000-08:00

sed -e "expression script"
-i to edit in place" Edit and save"

Sed How to Replace slash / And backslash \ character
Slash / represent as Normal /
backslash \ represent as \\
Example:
# cat sedlinux.txt
hi/kumar\kumar/
a)sed 's:\\:/:g' sedlinux.txt [ change back slash \ into slash / ]
hi/kumar/kumar/
b)sed 's:/:\\:g' sedlinux.txt [ change slash / into back slash \ ]
hi\kumar\kumar\

#sed 's:/var/www/html:/home/username:g' filename
|Replace /var/www/html to /home/username
#sed -n '1~3p' filename | Print Every 3rd Line 1st,1+3 4th,7th line.
#sed -n '0~2p' filename | Print Every 2nd LIne 0st,2nd,4th,6th,

#sed '3i New Line' filename.txt | It will add New Line On 3rd Line.
#sed -n '0~2i word' file | Add the new line in 0,2,4,6 th Line.

To delete the line with matching Character

#sed -i '/matchword/d' phone.txt
#sed -i '/^$/d' phone.txt - ^$ it will delete the empty lines
#sed '0~2d' filename - d Delete Line - 0,2,4,6

Replace every second occurrence in the line.
#sed ‘s/Search_Word/Replace_Word/2’ filename
Sed Replace with variable
#sed “s/$Search_Variable/$Replace_Variable/g” filename

Recover Deleted Log Files without Third Part Software Linux.

2011-11-08T03:28:00.000-08:00

CONDITION:
1)without rebooting server.
2)we can get Only the Log files in this method.

LOG FILES are Generated In Two ways
1)syslog Daemon.
Example : -maillog,cron,var-log-message,
2)Using File Descriptor Without syslog Daemon
Example : http,
Note : Using File Descriptor (Input,Output,Error redirection) Generate Log Files.

STUDY:
#cat /proc/"Process ID"/fd List out the file descriptor file which are used by these specific Process ID.

Using syslog Daemon Recovering Log Files
1)Find the Process Id Of the syslog Daemon
#ps -ef | grep syslog
2)List out the Specific Process ID File Descriptor Files.
#ll /proc/"PID of syslog"/fd/
For Example if PID is 1947 then,
# ll /proc/1947/fd/
lrwx------ 1 root root 64 Nov 4 12:38 0 -> socket:[4341]
l-wx------ 1 root root 64 Nov 4 12:38 1 -> /var/log/messages
l-wx------ 1 root root 64 Nov 4 12:38 2 -> /var/log/secure
l-wx------ 1 root root 64 Nov 4 12:38 3 -> /var/log/maillog
l-wx------ 1 root root 64 Nov 4 12:38 4 -> /var/log/cron
l-wx------ 1 root root 64 Nov 4 12:38 5 -> /var/log/spooler
l-wx------ 1 root root 64 Nov 4 12:38 6 -> /var/log/boot.log
l-wx------ 1 root root 64 Nov 4 12:38 7 -> /var/log/news/news.crit
l-wx------ 1 root root 64 Nov 4 12:38 8 -> /var/log/news/news.err
l-wx------ 1 root root 64 Nov 4 12:38 9 -> /var/log/news/news.notice
3)Even Though we deleted that file, it has some soft link access. Using these features.
we can recover these file.
For example : if we want to recover /var/log/cron file. then
l-wx------ 1 root root 64 Nov 4 12:38 4 -> /var/log/cron
#cp -var 4 /tmp/cron.backup

Recover Log file for Specific Service Which are Not maintain by syslog Daemon
1) This is also the same Method. But find out the Particular service Process Id rather than syslog Daemon PID. For Example http Service.
#ps -ef | grep http
# lsof -p "PID of http" | grep log
2) Remaining Same as the Above Method.
#ls /proc/"PID of http"/fd

Device eth0 has different MAC address than expected

2011-11-08T03:16:00.000-08:00

While I am changing My hard Disk from One Mother Board to Another Mother Board.
I got the following error message. it was booting perfectly. But while I restart the Network I got the Following Error message.

Error Message : #service network restart
Bringing up interface eth0: Device eth0 has different MAC address than expected, ignoring.
REASON : Because In the /etc/sysconfig/network-script/ifconfig-eth0 file MAC Address Assign as the Old Mother Board Ether net Mac Address. so While I restart Network service /etc/sysconfig/nework-script/ifconfig-eth0 Mac Address and Physical MAC Address Both Are different. Due to that We got the Above Error Message.
SOLUTION :
1) get the Local Mother Board MAC Address.
# dmesg | grep "Ethernet Address"
eth0: Ethernet Address: 00:0D:61:90:AE:4A
2)Update these Ethernet MAC Address into that corresponding file/etc/sysconfig/network-scripts/ifcfg-eth0
3)Then restart the Network Service.It will work Perfectly.
Bringing up interface eth0: Device eth0 has different MAC address than expected, ignoring.

Booting Error Message | Grub Loading Stage2 Read Error

2011-11-08T03:09:00.000-08:00

After I change the Linux Hard disk,
While booting Linux OS . I got the following Error message.

ERROR MESSAGE: Grub Loading Stage2 Read Error

REASON: Hard Disk Cable is not Connected Properly.

SOLUTION- : change the Hard disk cable Or Remove and Plug it Again then try it.
Grub Loading Stage1 & Grub Loading stage2 Error Message. Maximum 80% it will solve by through changing the cable. If we get grub > shell then only we should re install the grub boot loader. To reinstall Grub Boot loader Refer this Link. Reinstall Grub Boot Loader

How Configure Shared Library Difference Between .a .so

2011-10-28T02:10:00.000-07:00

Whenever we install the Open source Application or Software Read me file Instruct us to add directory of shared Library to $LD_LIBRARY_PATH Environment Variable to /etc/.bashrc file.
$LD_LIBRARY_PATH - Environment Variable for Shared Library Loader.

Difference Between Shared Library Files .a .so
Libraries are linked Either statically or Dynamically.
.so files are DYNAMIC library files.
which are loaded /unloaded and linked to an Executable at runtime.
.a files are STATIC library that get linked to code at a compile Time.
To check the Shared library Dependency we can use ldd command.
It is an ar archive

Shared Library Files Configure Important command.
ldd- List Dynamic Dependency.
# ldd /usr/bin/w – These are Dynamic Dependency files for w binary files.
libproc-3.2.3.so => /lib/libproc-3.2.3.so (0x00cb5000)
libc.so.6 => /lib/tls/libc.so.6 (0x00b8a000)
/lib/ld-linux.so.2 (0x00b6d000)

lddconfig - Configure Dynamic Link Library.
How to Configure Shared Library permanently .
Add New Library Path into /etc/ld.so.conf (or) We have to add Any Library Path could be place in any file,whose name end with *.conf file Inside /etc/ld.so.conf.d/ like /etc/ld.so.conf.d/myapp.conf
Activates the Path
#ldconfig
For confirmation (or) Verification
#ldconfig -v | grep "New Library Path"

ldconfig - configure dynamic linker run time bindings.
Common Library Path.
/usr/lib Standard System Libraries.
/usr/X11R6/lib/ X11 Libraries.
How to Compile the Program with Shared Library for X server Program
#gcc -Wall program.c -o output -L /usr/X11R6/lib -l X11
-L share Library Directory
-l Search
-Wall Warning Message
#ld - GNU Linker

Install Font in Redhat Linux Simple 4 Step

2011-10-18T03:35:00.000-07:00

1)Download the Font which one you want ot install.
2)open Nautilus window and type "fonts:///"
3)Drag the Font into that Nautilus Window (Fonts:///)
4)Immediately you can't see that font' here.

Verification
1)Just Log out then Log in,
2)For then check whether that font is Take the effect or Not.
Note: System->Preference-> Fonts

Backup Restore MBR And Partition Table Linux

2011-10-14T00:30:00.000-07:00

1)Master Boot sector it is 512 bytes
2)Locate at the First Sector in Hard Disk or Storage Device
3)MBR Total Size 512 Bytes
Bootstrap = 446 bytes
Partition Table = 64 bytes
Signature = 2 bytes

Backup Only Master Boot Sector Not Partition Table
#dd if=/dev/sda of=/tmp/mbr.bak bs=512 count=1
Restore
#dd if=/tmp/mbr.bak of=/dev/sdb bs=446 count=1

Backup Only the Partition Not Master Boot Sectore MBR
#dd if=/dev/sda of=/tmp/part.bak bs=512 count=1
Restore
#dd if=/tmp/part.bak of=/dev/sdb bs=1 count=64 skip=446 seek=446

How to Create the Boot Load in MBR Refer the Link Restore Recreate Lost MBR Grub Boot Loader Linux

Create New Partition Slice | Backup the Partition Table In Unix

2011-10-13T23:23:00.000-07:00

After Adding the New Disk To detect Unix OS Refer Following Method.
How To ADD New Device
1)METHOD 1
a)init 0
b)ok Prompt type setenv auto-boot? False

c)Power Off Workstation

d)Install New Disk

e)Power On Workstation
f)Ok Prompt type setenv auto-boot? True
g)boot -r
2)METHOD 2
a)touch /reconfigure
b)reboot
3)METHOD 3
a)devfsadm -c device_class
Fore Example Hard Disk
#devfsadm -c disk
Method 3 Is Simple and Best Method To ADD New Device.

Create the Partition Slice In Unix Operating System.
Using Format Disk Utility we can create the table in Unix Operating System
-bash-3.00# format [ it will show the List of disk ]
Searching for disks...done
AVAILABLE DISK SELECTIONS:
       0. c0d0
          /pci@0,0/pci-ide@1,1/ide@0/cmdk@0,0
       1. c0d1
          /pci@0,0/pci-ide@1,1/ide@0/cmdk@1,0
Specify disk (enter its number):2   [ Choose the Disk ]
format> part
WARNING - This disk may be in use by an application that has
          modified the fdisk table. Ensure that this disk isS
          not currently in use before proceeding to use fdisk.
format> fdisk [ Prepare Disk For Creating The Partition ]
No fdisk table exists. The default partition for the disk is:
a 100% "SOLARIS System" partition
Type "y" to accept the default partition, otherwise type "n" to edit the
partition table.

format> part [ Used For create the Partition ]
PARTITION MENU:
        0      - change `0' partition
        1      - change `1' partition
        2      - change `2' partition
        3      - change `3' partition
        4      - change `4' partition
        5      - change `5' partition
        6      - change `6' partition
        7      - change `7' partition
        select - select a predefined table
        modify - modify a predefined partition table
        name   - name the current table
        print - display the current table
        label - write partition map and label to the disk
        ! - execute , then return
        quit
Oracle Solaris we can create the 7 Slice.
In the second partition it show the whole Hard disk size
partition> print
Current partition table (original):
Total disk cylinders available: 4092 + 2 (reserved cylinders)
Part      Tag    Flag     Cylinders        Size            Blocks
0 unassigned    wm       0               0         (0/0/0)           0
1 unassigned    wm       0               0         (0/0/0)           0
2     backup    wu       0 - 4091        7.99GB    (4092/0/0) 16760832
3 unassigned    wm       0               0         (0/0/0)           0
4 unassigned    wm       0               0         (0/0/0)           0
5 unassigned    wm       0               0         (0/0/0)           0
6 unassigned    wm       0               0         (0/0/0)           0
7 unassigned    wm       0               0         (0/0/0)           0
8       boot    wu       0 -    0        2.00MB    (1/0/0)        4096
9 alternates    wm       1 -    2        4.00MB    (2/0/0)        8192
partition> 0 [Create the Partition 0 ]
Part      Tag    Flag     Cylinders        Size            Blocks
0 unassigned    wm       0               0         (0/0/0)           0
Enter partition id tag[unassigned]:
Enter partition permission flags[wm]:
Enter new starting cyl[0]:
Enter partition size[0b, 0c, 0e, 0.00mb, 0.00gb]: 3g

After create the all the slice print the Partition using print (or) pr command
partition> pr   [Print the Partition Table]
Current partition table (unnamed):
Total disk cylinders available: 4092 + 2 (reserved cylinders)

Part      Tag    Flag     Cylinders        Size            Blocks

  0 unassigned    wm       0 - 1535        3.00GB    (1536/0/0)  6291456

  1 unassigned    wm       0 -  255      512.00MB    (256/0/0)   1048576

  2     backup    wu       0 - 4091        7.99GB    (4092/0/0) 16760832

  3 unassigned    wm       0 -  255      512.00MB    (256/0/0)   1048576

  4 unassigned    wm       0               0         (0/0/0)           0

  5 unassigned    wm       0 -  255      512.00MB    (256/0/0)   1048576

  6 unassigned    wm       0 -  255      512.00MB    (256/0/0)   1048576

  7 unassigned    wm       0 -  255      512.00MB    (256/0/0)   1048576

  8       boot    wu       0 -    0        2.00MB    (1/0/0)        4096

  9 alternates    wm       1 -    2        4.00MB    (2/0/0)        8192

Finally save the table using name command.
partition> name [Create the Table name for Partition]
Enter table name (remember quotes): Partition-table- name
Finally write the table using label command
partition> label - [ Save the Partition To Disk ].

How To Backup The Hard Disk Partition Table - Import To New Hard Disk
prtvtoc - Print the Volume of Table content
fmthard - Update the Vtoc(Volume Table of Content).
a)prtvtoc /dev/rdsk/c3d0t0s2 > /tmp/c3t0d0.vtoc
b)fmthard -s /tmp/c3t0d0.vtoc /dev/rdsk/c4d1tos2

We can import the hard disk Directly in single Hard Disk
a)prtvtoc /dev/rdsk/cxtxdxs2 | fmthard -s - /dev/rdsk/cxtxdxs2

Note - For backup and Restore we have to Mention the Slice 2

Error Message :
-bash-3.00# fmthard -s /tmp/c0d1s2.vtoc /dev/rdsk/c1d1s2
fmthard: Partition 2 specifies the full disk and is not equal
full size of disk. The full disk capacity is 16760832 sectors.
fmthard: Partition 2 specified as 16764928 sectors starting at 0
does not fit. The full disk contains 16760832 sectors.
fmthard: New volume table of contents now in place

While Update the vtoc if we get any error message even though both Hard Disk are the same disk space. To Resolve that issue. Just create the one partition In the new disk. then try it, it will work perfectly.

Shell Scripting Important Syntax for loop Switch Case

2011-10-13T14:18:00.000-07:00

Important If Condition, For Loop While Loop
if Condition : Syntax
If { condition }
then {statement}
elif {condition }
{statement }
fi
Example
If [ $a ==10 ]
then
echo “value is Ten”
else
echo “Value is not Ten”

fi

For Loop- Method -1
For ( ( c=1;c<=5;c++))
do
echo “ Welcome $c times “
done

Method 2
for c in 1 2 3 4 5
do
echo "welcome $c Times"
done
Method 3
for c in {1..5}
do
echo "welcome $c Times"
done

Number comparison in shell script
--eq
--ne
--lt
--gt
-ge

Read variable in shell script
read { variable name }

While Loop Statement
c=3;
while [ $c -le 15 ]
do
echo "Welcome $c times"
((c++))
done

Switch case Example
Check=1
Case $check in
1) echo “redhat;;
2) echo “ubunut” ;;
*) echo “none”
esac
Trigger the Back Ground Process to foreground
Process Id Vary from 0 to 65535

Shell Script How To Do The Addition With Variable
S=$((10+$i)) just like for loop for ((;;))

How To Install Vlc Player In Redhat Linux Using Yum

2011-10-10T04:35:00.000-07:00

How to Create Repo File *.repo For vlc
1)Repo file located under /etc/yum.repos.d/ with *.repo extension
LINE 1)[name ]
LINE 2)Name of the Repo
LINE 3)BaseURL = Location of the Repo - /repodata/ *.xml.gz
LINE 4)gpgcheck 1/0 Enable/Disable
LINE 5)enabled

create vlc.repo file under /etc/yum.repos.d/
LINE 1)[vlc]
LINE 2)name=vlc
LINE 3)baseurl=http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/
LINE 4)enabled=1
LINE 5)gpgcheck=0
2)yum install vlc
So that, First it will download vlc packages.
Then it will install the vlc player.

Repo File BaseURL - http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/
1)It should have sub directory Name "repodata"
2)Under Here it has file name with extension .xml.gz and .xml
then only it should work perfectly
For Example Base URL
condor-Development - http://www.cs.wisc.edu/condor/yum/development/rhel5
VLC - http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/

If we are not Give the Correct baseurl. For then, it will through Following error message.
#yum install vlc
http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/RPMS/repodata/repomd.xml: [Errno 14] HTTP Error 404: Not Found
Trying other mirror.
http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/RPMS/repodata/primary.xml.gz: [Errno 14] HTTP Error 404: Not Found
Trying other mirror.
Error: failure: repodata/primary.xml.gz from vlc: [Errno 256] No more mirrors to try

Becuase -
repodata/repomd.xml-
repodata/primary.xml.gz
Both of these files are not present here.
Due to that reason,it is through Error message.Install vlc player in Redhat Linux

Check Linux Server Before Troubleshooting The Problem

2011-09-29T06:28:00.000-07:00

1)Study About that Server
Hard disk-Ethernet-RAM(Memory)-OS-Kernel-Version-Hostname.

2)check status of iptables- firewall,selinux-
top-free-df

3)Read the Log Message /var/log/message or dmesg

4)Backup of the Important configuraiton file
/etc/fstab-/boot/grub/grub.conf

5)check the hard disk speed using hdparm

6)Most Of the problem resolved by through reading the error message,

7)Read basic important entries in the file.
hostname - fully Qualified Domain Name, Ethernet address eth0, and security limit /etc/security/limit.conf,ulimit -l
So that Read The Error Message Clearly and Slowly. Get the Logical idea Regarding what is reason for this problem.

Some of the Comman Error Message And Solution.

For Comman Booting Problem Common Booting Problem

NFS Error MESSAGE - NFS ERROR: NFS Server Hostname failed:RPC Error: Program not registered

VNCVIEWER Error Message vncviewer unable to open display

SSH Error Must Be Owned By Root Not Group Or World

Display Error Failed To Start The X Server

Ssh Login Error Connect To Host IP port 22: Connection Refused

Outlook Express Configuration Error message Error Number: 0x800CCC79

How to Configure cluster.conf Active Active Cluster

2011-09-29T04:26:00.000-07:00

#system-config-cluster Graphical Window Interface.
we can create the cluster.conf file.

1)Create the Failover Domain
Creates Nodes with Priority.
2)Create the Resource
3)Create the the service.
3.1)Add the Resource To the Service then
3.2)add Fail over Domain(nodes with priority).
4)1 is Higher Priority.

How to Read cluster.conf file in Fail over Domain.
1) Check the service tag
service it will try to start their service in theFail over domain.
2.1)In the Failover domain which node has highest Priority.
In that highest priority Node it will try to start their service.
2.2)If the Highest Priority node is Down,
THEN -- It will check the next Lowest priority node.
IF LOWEST PRIORTY Node UP then --It will run that service at lowest priority node,
when will the Highest priority node is up. In that Time
without Human interaction service will automatically migrate from the Lowest Priority Node to Highest Priority Node.

Example of Cluster.conf file
<?xml version="1.0" ?>
<cluster config_version="9" name="Test_cluster">
    <fence_daemon post_fail_delay="0" post_join_delay="3"/>
    <clusternodes>
        <clusternode name="hn1.redhat.com" nodeid="1" votes="1">
            <fence/>
        </clusternode>
        <clusternode name="hn2.redhat.com" nodeid="2" votes="1">
            <fence/>
        </clusternode>
    </clusternodes>
    <cman expected_votes="1" two_node="1"/>
    <fencedevices/>
    <rm>
        <failoverdomains>
            <failoverdomain name="first" ordered="1" restricted="0">
                <failoverdomainnode name="hn1.redhat.com" priority="1"/>
                <failoverdomainnode name="hn2.redhat.com" priority="2"/>
            </failoverdomain>
            <failoverdomain name="second" ordered="1">
                <failoverdomainnode name="hn1.redhat.com" priority="2"/>
                <failoverdomainnode name="hn2.redhat.com" priority="1"/>
            </failoverdomain>
        </failoverdomains>
        <resources>
            <ip address="151.8.18.55" monitor_link="1"/>
            <ip address="151.8.18.56" monitor_link="1"/>
        </resources>
        <service autostart="1" domain="first" name="IP Address-55" recovery="relocate">
            <ip ref="151.8.18.55"/>
        </service>
        <service autostart="1" domain="second" name="IP Address -56" recovery="relocate">
            <ip ref="151.8.18.56"/>
        </service>
    </rm>
</cluster>

Failover Domain
1)hn1.redhat.com
2)hn2.redhat.com

Resource
1)IP Address 151.8.18.55
2)IP Address 151.8.18.56

Service
1)IP Address -55
2)IP Address -56

Update The Cluster.conf file
# ccs_tool update /etc/cluster/cluster.conf
Config file updated from version 27 to 28
Update complete.

# cman_tool nodes
Node Sts   Inc   Joined               Name
   1   M    632   2011-09-16 06:26:53 hn1.redhat.com
   2   M    636   2011-09-16 06:26:53 hn2.redhat.com

#ip addr list -- Get the virtual Ip Address
------------------------------------------------------
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 08:00:27:06:76:c7 brd ff:ff:ff:ff:ff:ff
    inet 151.8.18.53/16 brd 151.8.255.255 scope global eth0
    inet 151.8.18.55/16 scope global secondary eth0
    inet6 fe80::a00:27ff:fe06:76c7/64 scope link

# clustat -l
Cluster Status for Test_cluster @ Fri Sep 16 06:44:36 2011
Member Status: Quorate
Member Name                             ID   Status
------ ----                             ---- ------
hn1.redhat.com                                 1 Online, Local, rgmanager
hn2.redhat.com                                 2 Online, rgmanager
Service Information
------- -----------
Service Name      : service:File system Mounting
Current State   : started (112)
Flags           : none (0)
Owner           : hn2.redhat.com
Last Owner      : hn1.redhat.com
Last Transition : Fri Sep 16 06:19:27 2011

Service Name      : service:IP Address
Current State   : started (112)
Flags           : none (0)
Owner           : hn1.redhat.com
Last Owner      : hn2.redhat.com
Last Transition : Fri Sep 16 06:27:18 2011

Relocate the Service
-r Resource
-m Node
#clusvcadm -r service-name -m host-name
# clusvcadm -r "IP Address-55" -m hn2.redhat.com
Trying to relocate service:IP Address to hn2.redhat.com...Success
service:IP Address is now running on hn2.redhat.com

#watch clustat
Update the Cluster Status

Mount the NFS
</resource><netfs export="/home/jkumar" force_unmount="0" fstype="nfs" host="151.8.18.46" mountpoint="/mnt" name="NFS" options=""/>
Mount Disk
</filesystem><fs device="/dev/sdb1" force_fsck="0" force_unmount="0" fsid="41420" fstype="ext3" mountpoint="/mnt1" name="sdb" options="" self_fence="0"/>

ssh Error - Must Be Owned By Root Not Group Or World

2011-09-14T08:14:00.000-07:00

# /etc/init.d/sshd start
Starting sshd: /var/empty/sshd must be owned by root and not group or world-writable. [FAILED]
ERROR:Starting sshd: /var/empty/sshd must be owned by root and not group or world-writable.
check the file permission for /var/empty
If it is full permission then it won't work.

REASON:

/var/empty/sshd does not set the correct permission

SOLUTION
1)we have to set the correct permission
#chmod go-w /var/empty
we have to remove the writable permission for group file name /var/empty- then only it should start sshd service perfectly.

Hard Disk Error - Currently Unreadable Pending Sectors smartd

2011-09-14T07:53:00.000-07:00

while I start the Linux system, Everyting Booting perfectly.
All the Service and Run level script,
But for the login session,
it is not giving any Login window, it just show the blue screen for long time.
While I check the Log

LOG MESSAGE

/var/log/message
Sep 5 12:23:37 Hostname smartd[3407]: Device: /dev/sdb, 14 Currently unreadable (pending) sectors
Sep 5 12:23:37 Hostname smartd[3407]: Device: /dev/sdb, 16 Offline uncorrectable sectors

About Smartd - Self Monitoring Analysics and Reporting Technlology Daemon.
1)used for checking IDE, SATA Hard Drivers.
2)Monitoring Reliability of the hard drive and Predict Drive failures.

SOLUTIION
Disable the smartd service.
Login into the single usermod then disable that service
#chkconfig smartd off
Then try it. It will work perfectly.
Note: if you still face any issue.
Boot directly into run level 3 then try startX command.
Booting Problem in /dev/sda /dev/sdb Pending Sector - Offline uncorrectable sectors.

Configure Kernel Source Code make menuconfig Upgrade New Kernel

2011-09-06T07:41:00.000-07:00

make menuconfig Features
1)configure the Linux kernel Source Code,
2)Allow to choose the Feature of the Linux kernel.
3)make menuconfig target in the Linux kernel makefile.
4)it is Located under /usr/src/kernel/'uname -r'
Example Path : /usr/src/kernels/2.6.18-238.el5-x86_64
Under these path we have to enter the following command.
#make menuconfig
It will open the window here we can configure kernel Features.
Dependencies are
a)Linux Kernel Source
b)Make tool
3)C compiler
4)ncurses - n curses Library

How To Upgrade New Kernel.

1) Download Kernel form the kernel.org, which one we need to install.

2) Extract .tgz into Kernel Source Directory /usr/src/kernels.

Ex tar kernel.tar.gz -C /usr/src/kernel

3) cd /usr/src/kernel/Kernel_Path_Name/

#make menuconfig -> choose the Features Depends on Requirement

#make Command Build the Kernel Module.

4)Build vmlinuz Package

#make bzImage -- it will Build the vmlinuz Package.

Root device is (3, 1)

Setup is 12760 bytes (padded to 12800 bytes).

System is 1995 kB

CRC accf1f38

Kernel: arch/x86/boot/bzImage is ready (#55)

Output Kernel File is

/usr/src/kernels/linux-2.6.30.4/arch/i386/boot/bzImage

4.1)Copy the bzimage into /boot directory in name of vmlinux-Kernel_version

#cp /usr/src/kernels/linux-2.6.30.4/arch/i386/boot/bzImage /boot/vmlinuz-2.6.30.4

5) create initrd image using mkinitrd Command.

#make modules_install

#mkinitrd /boot/initrd-Kernel_version.img Kernel_version

If we are not making modules_intall then we will get the following Error Message.

# mkinitrd /boot/initrd-2.6.30.4.img 2.6.30.4

/lib/modules/2.6.30.4 is not a directory.

6) Edit the grub.conf file with New Kernel and initrd image.

Then reboot the system from the New Updated Kernel.

Virtual Box Hangs Whole System While Booting

2011-09-05T08:10:00.000-07:00

After Install the virtual Box in my Linux System.while I start the virtual box then it is going to hangs on my whole system.I can't use my Keyboard and Mouse. To again get back my system simply I have to restart the whole machine.

REASON

Remove the Module kvm-intel,ksm,kvm,
To List out moudule use #lsmod | grep kvm

SOLUTION

kvm - Kernel based Virtual Machine.
it is Virtualation Infrastruture for Linux kernel.
ksm- Kernel Semepage Mergning.
To run he virtualbox in the Linux system , we should remove the following module.
#rmmod kvm
#rmmod kvm-intel
#rmmod ksm
#modprobe -r kvm - To remove Permentaly
Then try it. Your Virtual Box will be working without any issu.
Note: Before we install the virtual Box, We should install dmks-Dynamic Kernal Module.
Virtual box going to hangs on the system while booting.

Failed To Start The X Server - Linux Display Error

2011-08-29T07:03:00.000-07:00

When I changed Linux system Monitor I got the following Error message while booting Graphical User Interface.
“Failed to start the X server (your graphical

interface). It is likely that it is not set

up correctly. Would you like to view the X

server output to diagnose the problem?”
- Yes

PROBLEM: When We changed Linux System Monitor the old screen resolution it is not supporable for New Monitor.Becuase Both Monitor Size is Different.

SOLUTION:Change the screen Resolution. Which is adoptable for New Monitor.
Log file: /var/log/xorg.o.log
Config File /etc/X11/xorg.conf

Then I got the following Message Box
"Would you like to try to configure the x server? Note that you will need the root password for this. "I Enter yes.
Finally it will open the "Display setting"- Here we can configure the New screen resolution According to the New Monitor.

Awk Command In Shell Script Print Field

2011-08-12T01:50:00.000-07:00

Study: a)/etc/dhcpd.conf file it contains all the Nodes Ethernet Mac Address.
b)awk Syntax - awk ' { print Argument }'
Example #ls -l | awk ' { print $2 }'
c)ether-wake Command Boot the Linux Server Remotely Using Mac Address.

1)# cat /etc/dhcpd.conf | grep ethernet
hardware ethernet 00:a0:d1:e9:b9:1a;
a)grep ethernet : grep Command It will filter the Particular Line which contain the string 'ethernet'.

2)# cat /etc/dhcpd.conf | grep ethernet | awk '{print $3}'
00:a0:d1:e9:b9:1a
b)awk '{print $3}' : It will the Print Third field.

3)#cat /etc/dhcpd.conf | grep ethernet | awk '{ print "ether-wake " $3 }'
ether-wake $3: ether-wake 00:a0:d1:e9:b9:1a.
Boot the Node which contain Mac Address 00:a0:d1:e9:b9:1a.

4)cat /etc/dhcpd.conf | grep ethernet | awk '{ print "ether-wake " $3 }' | sh
Whenever try the above Command Without | sh it will just print it will not execute the command.
like ether-wake 00:a0:d1:e9:b9:1a;
When we try with | sh then only it will execute that command.
sh It will execute the Command.

Actual Command - mv $9 $9.new
A)Note:Whenever we run the command Inside awk we have to put Inside " ".
Like:ls -l | awk '{ print "mv "$9" "$9".new" } '
B)Note: also for Every separate Variable
ls -l | awk '{ print "mv "$9" "$9".new" }

Some Examples with Awk Command
1)Using Mac Address Boot the all the Linux system
#cat /etc/dhcpd.conf | grep ethernet | awk '{ print "ether-wake "$3""}' | sh

2)Get the what are the Process (or) Command used for particular Directory or Partition
# fuser -m /opt/ | awk '{ print "ps -ax | grep "$2"" }' | sh

3)Print the List of Folder In Specified Format
# ls -l | awk '{ print "echo -n ---"$9">>scritp-output" }' | sh
` tilde Symbol
# awk ' { print $0 }'
$0 Whole Line $1 First Pattern
With Sorting List Only Unique Word
#cat a | sort | uniq
Without Sorting List only the Unique Word
# awk '!x[$0]++'
List out Duplicate word (or) what are words are repeat more than one times
# awk 'x[$0]++' a

Update Hosts File - Change Linux Server Hostname Without Reboot

2011-08-11T22:47:00.000-07:00

Object: To change The Hostname into client system For Particular Range of the Hostname Using Shell script.
Study:Without Rebooting the Linux Server We can change the Host name using Linux host name command
#hostname serverhostname
Now we are doing these Throught the Shell script.
Scenario : Now we have 10 nodes with hostname like node1,node2.. node10.
1)So using ssh connectivy 'ssh node1' it will login.then
2)hostname serverhostname - change their host name without reboot server

Shell Scripting

for((i=1;i<=10;i++));
do
ssh node$i 'hostname node'$i'.redhat.in';
done
we have to add Symbol ' ' the variable $i
becuase it is already Inside the Phare of ' '

Wrong Format

ssh node$i 'hostname node$i.redhat.in';

Coorect Format

ssh node$i 'hostname node'$i'.redhat.in';
How to change Linux server Hostname without Rebooting the Linux Server.

Update Hosts file Without Rebooting
If we are adding any new host to the /etc/hosts file.Then to update this hostfile use hostname -F filename
#hostname -F /etc/hosts
To update the hosts file /etc/hosts.
hostname -d - Display Domain Name
hostname -a - Alias
hostname -i - IP Address

Check InfiniBand Speed Performance Information

2011-08-11T03:01:00.000-07:00

InfiniBand Different Types
4X = 4 * Infiniband Link Rate 2.5 Gbits/sec, which is
Equal to (2.5*4)10Gbits/sec, Full Duplex.
SDR= Single Data Rate - 10Gbits/sec
DDR = Double Data Rate - 20Gbits/sec
QDR = Quad Data Rate- 40Gbits/sec

Check the Infiniband OFED Version
# ofed_info | head -n 1
MLNX_OFED_LINUX-1.4 (OFED-1.4-mlnx8)

InfiniBand Self Test
# /usr/bin/hca_self_test.ofed
---- Performing Adapter Device Self Test ----
Number of CAs Detected ................. 1
PCI Device Check ....................... PASS
Kernel Arch ............................ x86_64
Host Driver Version .................... MLNX_OFED_LINUX-1.5.3-1.0.0 (OFED-1.5.3-1.0.0): 1.5.3-2.6.18_194.el5
Host Driver RPM Check .................. PASS
Firmware on CA #0 HCA .................. v1.2.0
Firmware Check on CA #0 (HCA) .......... NA
REASON: NO required fw version
Host Driver Initialization ............. PASS
Number of CA Ports Active .............. 1
Port State of Port # on CA #0 (HCA)..... UP 4X (IB)
Error Counter Check on CA #0 (HCA)...... PASS
Kernel Syslog Check .................... PASSib_rdma_lat
Node GUID on CA #0 (HCA) ............... 00PORT_ACTIVE:02:c9:02:00:2a:78:b8
------------------ DONE ---------------------

Find the Infiniband Speed Status of the host Topology
# /usr/sbin/iblinkinfo.pl
Switch 0x000b8cffff006c98 MT47396 Infiniscale-III Mellanox Technologies:
21 1[ ] ==( 4X 2.5 Gbps Active/ LinkUp)==> 22 1[ ] "node1 HCA-1" ( )
21 2[ ] ==( 4X 2.5 Gbps Active/ LinkUp)==> 2 1[ ] "node2 HCA-1" ( )
21 3[ ] ==( 4X 2.5 Gbps Active/ LinkUp)==> 1 1[ ] "node3 HCA-1" ( )
21 4[ ] ==( 4X 2.5 Gbps Active/ LinkUp)==> 3 1[ ] "node4 HCA-1" ( )
21 5[ ] ==( 4X 2.5 Gbps Active/ LinkUp)==> 4 1[ ] "node5 HCA-1" ( )
21 6[ ] ==( 4X 2.5 Gbps Active/ LinkUp)==> 5 1[ ] "node6 HCA-1" ( )
Fine the Infniband host Topology
# ibhosts
Ca : 0x0002c902002a78d0 ports 1 "ib-node1 HCA-1"
Ca : 0x0002c902002a78d4 ports 1 "ib-node3 HCA-1"
Ca : 0x0002c902002a78bc ports 1 "ib-node7 HCA-1"
Ca : 0x0002c902002a79a0 ports 1 "ib-node5 HCA-1"
Inifniband Hardware Swith Details.
# ibswitches
Switch : 0x000b8cffff0071cc ports 24 "MT47396 Infiniscale-III Mellanox Technologies" base port 0 lid 9 lmc 0

Infiniband kernel can Configuration Information.
# /etc/infiniband/info
prefix=/usr
Kernel=2.6.18-194.el5
Configure options: --with-core-mod --with-user_mad-mod --with-user_access-mod --with-addr_trans-mod --with-mthca-mod --with-mlx4-mod --with-mlx4_en-mod --with-mlx4_ib-mod --with-mlx4_vnic-mod --with-mlx4_fc-mod --with-cxgb3-mod --with-nes-mod --with-qib-mod --with-ipoib-mod --with-sdp-mod --with-srp-mod --with-rds-mod --with-iser-mod
# ibv_devinfo
hca_id: mthca0
transport: InfiniBand (0)
fw_ver: 1.2.0
node_guid: 0002:c902:002a:78b8
sys_image_guid: 0002:c902:002a:78bb
vendor_id: 0x02c9
vendor_part_id: 25204
hw_ver: 0xA0
board_id: MT_03F0110001
phys_port_cnt: 1
port: 1
state: PORT_ACTIVE (4)
max_mtu: 2048 (4)
active_mtu: 2048 (4)
sm_lid: 1
port_lid: 5
port_lmc: 0x00
link_layer: IB
Status of the Infiniband
# ibstatus
Infiniband device 'mthca0' port 1 status:
default gid: fe80:0000:0000:0000:0002:c902:002a:78b9
base lid: 0x5
sm lid: 0x1
state: 4: ACTIVE
phys state: 5: LinkUp
rate: 10 Gb/sec (4X)
link_layer: IB

Create User Quota Luster File System

2011-08-01T12:56:00.000-07:00

1)when ever we create the user, first create user in mds - Meta Data Server
2)Then create same user in the client system.
3)Create the same user in mds and client with same User Id
#useradd -u 1000 new
If we create the same User id Then only it will work perfectly.

HOW TO CREATE QUOTA IN THE LUSTER
#lfs quotaon -ugf /home
If quota is not enable then we will get the following message.if it is off
# lfs quotaoff /home/
# lfs quota /home/
user quotas are not enabled.
group quotas are not enabled.
#lfs quota /home-- list quota

List quota For particular User
#lfs quota -u new -v /home/
#useradd -g sg qtest

Set The Quota

# lfs setquota -u new --block-softlimit 2048 --block-hardlimit 3048 /home/new/
#lfs quotacheck /home -- update the quota
To Verify the Quota
[new@node1 ~]$ dd if=/dev/zero of=/home/new/onew.iso bs=1024KB count=2
dd: writing `/home/new/onew.iso': Disk quota exceeded
dd: closing output file `/home/new/onew.iso': Input/output error
#lfs getstripe /home/username/file.img

Operating System Not found Linux Hard Disk Problem

2011-08-01T08:11:00.000-07:00

Scenario : When I boot the Linux Operating System, I got the Following Error message - Operating System Not Found.
1) I have the two hard disk, /dev/sda and /dev/sdb.
2) When Both Hard disks are present it is booting Perfectly.
a) When I remove the Second Hard disk /dev/sdb I got " Operating system not found"
b) When I remove the First Hard disk I got "Grub"

Reason:

1) Booting files /boot/grub/grub.conf are located in /dev/sda
2) MBR Grub is located in /dev/sdb
Some Other criteria
1) Hard disk does not contain the any Operating System,
Due to this only we got the following Error Message.
Operating System Not Found -Error Message

Solution

To resolve this problem First we have to change the grub MBR into First hard Disk.
1) First I boot From Linux CD the Rescue mode.
2) Rescue Mode mount Hard disk File system under /mnt/sysimage
Try the following command to resolve
#chroot /mnt/sysimage
#grub
grub>find /boot/grub/stage1
If File you Got "Error 15: File not found" then try
grub>find /grub/stage1
Then You will get like (hd0,0) or (hd0,4)
grub>root(hd0,0)
grub>setup(hd0,0)
It will install grub Boot loader in (hd0,0)
Then restart the server your system will be booting perfectly. Operating System not found. Grub Error-How to Resolve.

Cluster.conf File Example Node Resource Service Failover Domain

2011-07-30T12:03:00.000-07:00

Storage OSS Server High Availblity Cluster Configuration /etc/cluster/cluster.conf file Example.
1)It has Two Nodes – Ost3 and ost4 – FailoverdomainNode
2)Two Failover Domain Name- OSS_Domain3- OSS_Domain4- failoverdomain name
3)Six Resource Are there Four Storage Two IP
Four Storage
a)ost5 - device - /dev/dm-0 – Mount Point –ost5
b)ost6 - device - /dev/dm-1– Mount Point –ost6
c)ost7 - device - /dev/dm-2– Mount Point –ost7
d)ost8 - device - /dev/dm-3– Mount Point –ost8
Two IP Resource
a) ip address="20.0.1.207/16
b) ip address="20.0.1.208/16
4)Two Service are There,
Each Service Has three Reource [ Two storage one ip]
These cluster Configured In Active - Passive Mode- What is Active Passive Mode

/etc/cluster/cluster.conf File Example
<?xml version="1.0"?>
<cluster alias="OSSS" config_version="24" name="OSSS">
<fence_daemon post_fail_delay="0" post_join_delay="3"/>
<clusternodes>
<clusternode name="oss3" nodeid="1" votes="1">
<fence>
<method name="1">
<device lanplus="" name="ipmi_oss3"/>
</method>
</fence>
</clusternode>
<clusternode name="oss4" nodeid="2" votes="1">
<fence>
<method name="1">
<device lanplus="" name="ipmi_oss4"/>
</method>
</fence>
</clusternode>
</clusternodes>
<cman expected_votes="1" two_node="1"/>
<fencedevices>
<fencedevice agent="fence_ipmilan" ipaddr="30.0.1.203" login="root" name="ipmi_oss3" passwd="root123" option="off"/>
<fencedevice agent="fence_ipmilan" ipaddr="30.0.1.204" login="root" name="ipmi_oss4" passwd="root123" option="off"/>
</fencedevices>
<rm>

</failoverdomain>

<failoverdomain name="OSS_Domain4" ordered="1" restricted="1">

<failoverdomainnode name="oss3" priority="2"/>

<failoverdomainnode name="oss4" priority="1"/>

</failoverdomain>

</failoverdomains>

<ip address="20.0.1.207/16" monitor_link="1"/>

<ip address="20.0.1.208/16" monitor_link="1"/>

</resources>

</service>

<service autostart="1" domain="OSS_Domain4" name="lustre_2" recovery="relocate">

<lustrefs ref="ost7"/>

<lustrefs ref="ost8"/>

<ip ref="20.0.1.208/16"/>

</service>

</rm>
</cluster>

High Availability Active-Active Active-Passive Failover Domain.

2011-07-30T11:46:00.000-07:00

Cluster High Availability It has Two Mode
1) Active-Active Mode
2) Active-Passive Mode

Active- Active Mode
1) Both Master server 1 and Master Server2 Both are Running Stages.
2) Active – Active Mode has two Failover Domain

ACTIVE & ACTIVE MODE – Luster File system OSS
---------------------------------------------------
<failoverdomain name="OSS_Domain3" ordered="1" restricted="1">
<failoverdomainnode name="oss3" priority="1"/>
<failoverdomainnode name="oss4" priority="2"/>
</failoverdomain>
<failoverdomain name="OSS_Domain4" ordered="1" restricted="1">
<failoverdomainnode name="oss3" priority="2"/>
<failoverdomainnode name="oss4" priority="1"/>
</failoverdomain>
Active & Active OSS Node it has two failover domains,

Active Passive Mode
1) One master Server Node 1 is Active and Master Server 2 is standby.
So if one server 1 Is down, Another Server 2 replace instead of that server 1.
2) Active passive Mode has one failover Domain.

ACTIVE & PASSIVE MODE -Luster File system MDS
------------------------------------------------
<failoverdomain name="MDS_Domain" ordered="1" restricted="1">
<failoverdomainnode name="mds1" priority="1"/>
<failoverdomainnode name="mds2" priority="1"/>
</failoverdomain>
Active & Passive Node it has only one failover domain.

High Availability Tag Field
1)/etc/cluster/cluster.conf – Cluster Configuration File.
2)Resource Start with <resource> and </resource>
Service it is like IP Address, Storage- Mount Point, Linux Service Like http,

Service it will come with Name like ost5
3)Service start with <service> and </service>tag
Create New service. Add Resource using rousrce name to the service.
<lustrefs ref="ost5"/>
4) failoverdomain start and end with <failoverdomain> and
</failoverdomain>
It has node name, <failoverdomainnode name="oss3" priority="2"/>

MDS OSS Server Creation Luster File system

2011-07-29T10:40:00.000-07:00

TO maintain the Luster File system, We have to create the MDS,OSS.
MDS SERVER CREATION IP-10.0.0.10

--mdt metadat Storage target
--ost Obeject storage target
--mgs Configruating the management service,
--fsname file system name
1)MDS it will only communicate between the oss and client
2)oss and client both are not pinging directly.
client node and oss both are pinging through the mds.
Syntax For Creating MDS
3)#mkfs.lustre --mdt --mgs --fsname=lustre /dev/sdb
4)#mount -t lustre /dev/sdb /mnt/mdt/
Note : while mounting take the another terminal try the following command
#tail -f /var/log/message -- we can known what is going background,

OSS SERVER CREATION IP -10.0.0.101
1)creation
While creating oss we have to mention the mgsnode Server IP
#mkfs.lustre --ost --fsname=lustre --mgsnode=10.0.0.10@tcp0 /dev/sdb
if you want to reformat
#mkfs.lustre --reformat --ost --fsname=lustre --mgsnode=10.0.0.10@tcp0 /dev/sdb
--mgsnode set the NIDS of the mgs node
2)mount -t lustre /dev/sdb /mnt/ost

CLIENT SIDE MOUNT OPTION -10.0.0.12
mount -t lustre 10.0.0.10@tcp0:/lustre /home
mount -t lustre mdsip:/lustre /home

VERIFY WHETHER IT IS MOUNTING PERFECTLY
[root@node1 Lustre-1.8.5]# lfs df -h
UUID bytes Used Available Use% Mounted on
lustre-MDT0000_UUID 1.7G 83.2M 1.6G 4% /home[MDT:0]
lustre-OST0000_UUID 2.0G 83.2M 1.8G 4% /home[OST:0]

filesystem summary: 2.0G 83.2M 1.8G 4% /home
These MDS, OSS Server Creation

Create Luster File system In Redhat Linux - Installation

2011-07-29T10:21:00.000-07:00

Linux+Cluster=Luster.
To main the Luster file system, We have to Install the Following 6 rpm package in Client,Object Storage Server(OSS),Meta Data Server(MDS),
To Install rpm package, use rpm -ivh
-i install
-v verose
-h hash
1)Even though we install the all package, e2fsprogs it is not install properly,
To check use rpm -qa command , So using rpm -Uvh update that package
2)Update the package
# rpm -Uvh e2fsprogs-1.41.10.sun2
Packages Are
1)e2fsprogs-1.41.10.sun2-0redhat.rhel5.x86_64.rpm
2)kernel-2.6.18-194.17.1.el5_lustre.1.8.5.x86_64.rpm
3)kernel-devel-2.6.18-194.17.1.el5_lustre.1.8.5.x86_64.rpm
4)lustre-1.8.5-2.6.18_194.17.1.el5_lustre.1.8.5.x86_64.rpm
5)lustre-ldiskfs-3.1.4-2.6.18_194.17.1.el5_lustre.1.8.5.x86_64.rpm
6)lustre-modules-1.8.5-2.6.18_194.17.1.el5_lustre.1.8.5.x86_64.rpm

Communcation Between Two Nodes,
For the communcation between the two node, We have to edit the in the modeprobe.conf file
1)we have to add entry in /etc/modprobe.conf
options lnet networks=tcp0(eth1)
#modprobe lnet [ update the driver]

List the Network
# lctl list_nids
IOC_LIBCFS_GET_NI error 100: Network is down

UP The Network
# lctl network up

LNET configured
# lctl list_nids
10.0.0.11@tcp0
Just like update the MDS, OSS and CLIENT,

To Check For Pinging Whether It is Pinging Or Not
[root@mds ~]# lctl ping 10.0.0.9@tcp
12345-0@lo
12345-10.0.0.9@tcp
These Are the Basic Luster Installation Step,

Yum Server Configuraiton In Simple 4 Step

2011-07-20T00:38:00.000-07:00

Copy From the Media Disk to the Local /opt Directory
1) cp -var /media/RHEL_5.5\ x86_64\ DVD/Server/ /opt/rpm/
2)Install createrepo rpm package.
rpm -ivh createrepo-0.4.11-3.el5.noarch.rpm

3)Using Createrepo Package create the repo package for /opt/rpm.
createrepo /opt/rpm/
228/3116 - foomatic-3.0.2-38.3.el5.x86_64.rpm

4)Edit the /etc/yum.repos.d/filename.repo

Before Edit the File

1[c5-media]
2name=CentOS-$releasever - Media
3baseurl=file:///media/CentOS/
4gpgcheck=1
5enabled=0

After Edit the File

1 [yumserver]
2 name=yum serve
3 baseurl=file:///opt/rpm/
4 gpgcheck=0
5 enabled=1
Note : change Line 3,4,5

Verfiy whether Yum Install Sucessfully Or Not

# yum clean all
Loaded plugins: fastestmirror
Cleaning up Everything
Cleaning up list of fastest mirrors
# yum list all
--------------------------
Server : [ ###################################### ]1223/2531
we have to get the these type of Output that confirm Yum installed succefully for this Server.
How to Configure Yum Server In Simple Step by step Installation Process

Samba Server Configuraiton In Simple 4 Step

2011-07-11T21:11:00.000-07:00

Install Configure Samba Server GUI Mode.

1)system->Administrator ->server setting->samba
It will Open the PoP up window.
File --> Add share

2)Basic(tab)
Add share Directory
2.1)Directory:
2.2)share Name:
2.3)Enable - writ ab, Vi sable

3)Access(tab)-Allow Access To everyone should be enable.
4)preference->Server Setting->security(tab)- > Authentication Mode:share

Note:

1)Disable the selinux & Iptables
2)we have to Give the Full permission to that share directory

From the Windows system-

1)start->run-> \\LINUX SAMBA SERVER IP\
Finally you can access that Linux directory from windows machine.
To Install Command Line Interface - Refer the Link.-Samba Server Configuration In CLI mode.
samba server Configuration In simple step by step Four step.
Easy way to Configure In 4 Four step

Run Execute Shell Script While System Booting Startup

2011-06-02T22:24:00.000-07:00

1)After write the shell script we have to place that shell script under /etc/init.d/.
2)Then add the following line to that shell script at the begining
#!/bin/bash
# chkconfig: 2345 95 20
# description: Some description
3)add into chkconfig
#chkconfig --add shellscript.sh
NOTE: if we did STEP:2) then only we can add using chkconfig
4)chkconfig shellscript.sh on

CONFIRMATION: To check if we go to /etc/rc.d/
we have 6 run runlevel script directory
rc0.d rc1.d rc2.d rc3.d rc4.d rc5.d rc6.d
if go to that direcotry we can see the shell scrip name with "S" & "K"
S indicate start the script when it boots up,
K metion down cleanly when it is going shut down
Soft Link syntax
ln -s [SOURCE FILE] [DESTINATION FILE]
For Manual Adding.
ln -s /etc/init.d/script-daemon-name /etc/rc.d/rc5.d/S50cript-daemon-name
ln -s /etc/init.d/script-daemon-name /etc/rc.d/rc5.d/K50script-daemon-name

How To Run Command while system Booting.

We can run the command using /etc/rc.d/rc.local
/etc/rc.d/rc.local - here what are command we put it will run while booting.
Using these method we can run the command shell script as daemon while booting or start up of the system.

Remote Desktop Vncviewer Enable Disable command Line

2011-06-02T03:25:00.000-07:00

IT IS ONLY FOR ENABLE THE CLIENT DESKTOP NOT FOR CONTROL

Remote Desktop Enable Disable through Command Line To ACCESS
ENABLE / DISABLE Remote Desktop
1)Enable the remote Desktop through command line Interface To access from other system
gconftool-2 -s -t bool /desktop/gnome/remote_access/enabled true
a)true -enable b)false -disable

Enable / Disable For CONFIRMATION
2)gconftool-2 -s -t bool /desktop/gnome/remote_access/prompt_enabled true -> enable the confirmation
if it is false mean - without confirmation you can access the system.
a)true - enable b)false - disable
To confirm
System -> Preferences -> Remote Desktop

Vnc Viewer Error Message Unable To Connect To Host

2011-06-02T03:02:00.000-07:00

While I try to connect the client system through Remote Desktop through vncviewer.I got the following error message.
unable to connect to host: Connection refused (111).
[root@remote]# vncviewer
VNC Viewer Free Edition 4.1.2 for X - built Mar 24 2009 19:53:14
Copyright (C) 2002-2005 RealVNC Ltd.
See http://www.realvnc.com for information on VNC.
Thu Jun 2 11:45:07 2011
main: unable to connect to host: Connection refused (111)

ERROR MESSAGE:

unable to connect to host: Connection refused (111)
REASON FOR PROBLEM
VNCSERVER it not starting (or) we are not open with appropriate vncviewerdesktopip:number

vncserver
1)it will start or stop vnc server.
2)vncserver it is used to virutal network desktop.
while vnc server start -it will create the following files
a)$HOME/.Xauthority
b)$HOME/.vnc/xstartup

Run these command 'vncserver' at the client System.
It will create Virtual Network Desktop
[uername@clientsystem]$ vncserver
You will require a password to access your desktops.
Password:
Verify:
xauth: creating new authority file /home/venkates/.Xauthority
New 'Venkates:3 (venkates)' desktop is Venkates:3
Creating default startup script /home/venkates/.vnc/xstartup
Starting applications specified in /home/venkates/.vnc/xstartup
Log file is /home/venkates/.vnc/Venkates:3.log
From the Remote system
[root@remote]#vncviewer cliensystemtip:Number
It will ask the password enter the password for which one you created at the eariler.

Linux Display Pop-up Window Message Box Mail Alert Notification

2011-06-01T00:24:00.000-07:00

In the Linux shell script How to create Linux pop-up window & Message Box, Mail alert. Display message notification.
1)gnome-terminal -x sh -c "date|less" >>run the command in new gnome-terminal
2)xterm -e "top -c; sleep 10"
Open the xterm terminal and run the command
3)notify-send "welcome to Linux message box"
4)echo "hello">>/dev/pts/2
pts- pseudo terminal slave / ptm - pseudo terminal master
/dev/pts/1 it is indicate about terminal device file.
5)wall "welcome to studentcpu.com"
It will send the message to All The user who are login.
6)cat msg.txt | wall
SEND MESSAGE TO REMOTE SYSTEM GUI
When we took the remote connectivity of the other system we can send Notification message to the Graphical windows using these method.using Terminal we can do that But through Graphical we have to export variable DISPLAY=:0.
7)export DISPLAY=:0 && zenity --info --title='Message' --text='Linux redhat '
When we took the remote connection for remote system we can display message on there Graphical window
Using export DISPLAY=0;
7)export DISPLAY=:0 && notify-send "we are looking for linux expert"
it will open small notification message box on the right hand side bottom corner.
9)kdialog --title "New Mail Has Arrived" --passivepopup \
"it will terminate withing 5 minutes" 5
Open the message Box on the Left Hand side Top bottom.

Hard Disk Management Logical Partition Extended & Primary Partition

2011-05-30T03:18:00.000-07:00

In the Linux partition /dev/sda4 is always consider as the extended partition.
Primary partition is used for maintain the operating system.
In the hard disk it has four primary partition,
while booting Only one primary partition is active and renaming partition it will ignore.
1)One of the Four primary partition can be assigned as extended partition.
So In the hard disk we have only one Extended Partition.
2)that extended partition can be divided into multiple logical volume,
3)Logical volume it can not be Primary Partition,
4)If we want to increase the partition
4.1) we can not increase the Primary partition
4.2) we need to increase the Logical partition from the extended, Here we can exteded upto 64 Logical volume,

Vim Editor Tutorial Tricks Tips Advanced Features

2011-05-30T01:56:00.000-07:00

1)Vim Editor Has the Three Different mode
a)Command Mode
b)Insert Mode
c)Last Line Mode (or) (:) colon mode
2)Vim Editor To Change Lower Case & Upper Case Vice Versa
In COMMAND MODE
gU - Change into UPPER CASE
gu - Change into Lower Case
3)Vim editor encryption To create Password To Edit and Save file
#vim -x filename.txt
Enter the encryption Key,
While You open next time it will ask password (encryption key).
4) How to print the output to the text file
Open the vim editor
#vim jkumar.txt
Unde the Last line mode (:) colon mode

:r!date

5)Auto Correct How to enable the spelling correct
:set spell - Enable spelling correct
:set nospell - Disable spelling correct
6)To get Help on Live

:help d

Just like we can get the output which one we want

Linux Essential Important Question Answer Tips Tricks

2011-05-30T01:47:00.000-07:00

While Copy Replace if the file is exist
1)#yes | cp Source Destination { while copy if the file is already present replace answer yes }
2)Search And delete the word
#sed "/search word/d" -i file
Partition Hard disk
3))Hard disk partition
/dev/sda1 (hd0,0)
/dev/sda5 (hd5,0)
4)rsync backup script under High availability
The Root partition.
#mount /dev/sda5 /mnt/hd
#rsync -ax / /mnt/hd
Using These method we can copy only the root partition, But we can't use these to maintain the separate system,
Because pid,dev it will not make the proper update,
5) script how to create current date as folder name.
# mkdir `date +%d-%m-%y.%H:%M:%S`
30-05-11.11:23:29
6)disk label in Linux
6.1)mkfs.ext3 -L HOME /dev/hda1
6.2)e2label /dev/hda2 SECONDARY_BACKUP
while Create Swap Space
6.3)mkswap -L SWAP /dev/hda5
While using in fstabe we can use like
LABEL=HOME /home ext2 defaults 0 0
7)How to check whether Cron tab job is working or not.
#cat /var/log/cron
May 30 11:30:01 jkumar crond[5844]: (root) CMD (/usr/lib/sa/sa1 1 1)
Using cron log we can identify whether job is running at a specific time.s
8)env - environment variable it is used to maintain or modify the environment variable.
#! These sysntax is used to mention the which interpreter is used to execute the program.
#!/bin/bash
#!/usr/bin/perl
#!/usr/bin/python
1)Shell script shebang also called a hashbang it is contain the character number sign(#) and exclamation point (#!),
2)it is give the absolute path for the interpreter
How to set the Proxy Entry in the Linux
9)export http_proxy=http://proxyip:portnumber
export http_proxy=http://151.8.27.214:6588 (or)
wget -Y -e "http_proxy=host:port" url

Infiniband For Hight perfomance Computing

2011-05-30T00:47:00.000-07:00

Infini band Is mainly used for High performance Computing because compare to Ethernet device it will provide High data transfer, it will provide Following features,
1)High throughput
2)Quality of Service
3)fail over
4)Provide High bandwidth,
Infiband throughput is upto 2.5 gigabytes per second.
By using Infinband we will get better Performance For HPC - High Performance Computing.
Infini Band Command- HPC
#/etc/init.d/openibd status
here we can try status,start,restart,
Ibstat Give the status about that command.
# ibstat
CA 'mthca0'
CA type: MT25204
Number of ports: 1
Firmware version: 1.2.0
Hardware version: a0
Node GUID: 0x0002c902002a798c
System image GUID: 0x0002c902002a798f
Port 1:
State: Initializing
Physical state: LinkUpOFED-1.5.3
Rate: 10
Base lid: 0
LMC: 0
SM lid: 0
Capability mask: 0x02510a68
Port GUID: 0x0002c902002a798d
Link layer: IB
If thee ste is State: Initializing to change state as Active try the following command, then try it.
# /etc/init.d/opensmd start
Compare to Ethernet Infni band is 25% better performance while transfer through infiniband ip
EXAMPLE:1 GB transfer it take 49 s [ethernet]
1 GB transfer it take 29 [infiniband]

/usr/bin/env: python2.3: Permission Denied No Such File Or Directory

2011-05-04T03:43:00.000-07:00

/usr/bin/env: python2.3: Permission denied
/usr/bin/env: python2.3: No such file or directory
# /usr/bin/env python2.4
/usr/bin/env: python2.4: No such file or directory
if you try from the Standard user
# /usr/bin/env python2.4
/usr/bin/env: python2.4: Permission denied

PROBLEM - ERROR MESSAGE

The problem is I have already installed the python2.3.
But MPI program Or Cluster application they are default set to use the python 2.4.So I need to redirect from python2.4 to python2.3.
Using Soft Link we can resolve that problem.
For python2.3 it is working perfectly for python2.3.
# /usr/bin/env python2.3
Python 2.3.4 (#1, Feb 18 2008, 17:16:53)
[GCC 3.4.6 20060404 (Red Hat 3.4.6-9)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>

SOLUTION

To Resolve these problem for python2.4
1)create the soft link for python2.4 to python2.3
#ln -sf (DESTIONATION) (SOURCE)
-s soft link
-f force
#ln -sf /usr/bin/python2.3 /usr/bin/python2.4
Then try it the problem has been cleared
/usr/bin/env: python2.4: No such file or directory
/usr/bin/env: python2.4: Permission denied

Hard Disk Partition Disk Label In Linux

2011-04-29T03:52:00.000-07:00

Linux Operating system , partition and there root grub.conf file parameter
hdx,y
x represent Hard disk,
Y represent Parition,
/dev/sda1 - (hd0,0)
/dev/sda2 - (hd0,1)
/dev/sda3 - (hd0,2)
/dev/sda4 - (hd0,4)
/dev/sda5 - (hd0,5)
Second Hard disk
/dev/sdb1 -(hd1,0)
/dev/sdb2 -(hd1,1)
/dev/sdb3 -(hd1,2)
/dev/sdb4 -(hd1,3)
/dev/sdb5 -(hd1,4)
If you want to make the second partition as boot partition
1)copy the boot partition document into /dev/sdax
2)create install using setup command
CHANGE BOOT PARTITION
Refer the below link

Operating system partition and there parameter.

Change Linux Boot Partition /dev/sda5 root(hd0,4) to /dev/sda1 root (hd0,0),

2011-04-28T23:58:00.000-07:00

Scenario : Under Linux Operating system, I have the two boot partition /dev/sda1 and /dev/sda5.currently it is booting from /dev/sda5 I want to change boot partition into /dev/sda1. How to change,How to address Master boot record boot partition from /dev/sda4 to /dev/sda1
Solution: when ever the Linux operating system boot, first it will load mbr (master boot record) these mbr load the grub loader(grub.conf).
To change these /dev/sda4/grub.conf to /dev/sda1/grub.conf mab follow the procedure.
1)grub>find /boot/grub/stage1
root(hd0,0)
root(hd0,4)
If you get any error message like

"Error 15: File not found"

Then try following command,
While we check "find /boot/grub/stage1" if it is not found,
Then can check "find /grub/stage1"
grub> find /grub/stage1
(hd0,0)
(hd0,4)
From these
Here I have two boot partition so it show the two parameter,(hd0,0), (hd0,4)
we need to confirm which partition we want to install that grub
2)grub>root (hd0,0)
3)grub>setup (hd0)
Running "install /grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
From there last line we can confirm the grub conf file located (hd0,0)/grub/grub.conf
4)Go to /dev/sda1-/etc/fstab add boot partition.
/etc/fstab
/dev/sda1 /boot
How to change Linux Booting partition from /dev/sda4 root(hd4,0) to /dev/sda1 root(hd0,0)
Change the boot partition.

Unable Start Stop NFS Daemon Failed

2011-04-25T03:39:00.000-07:00

I try to install the client system through kickstart with NFS service,
For client installation it is unable to get the kick start file, it asking for kick start file,these type of issue will happened when nfs service is failed.So I try to start restart the nfs service, While start nfs deamon start and stop are failed.
# service nfs start
Starting NFS services: [ OK ]
Starting NFS quotas: [ OK ]
Starting NFS daemon: [FAILED]
If the nfs Service is stop,

1)due to that unable to get Kickstart file it can not go ahead for installation.
2)So we have to restart the nfs service
while I restart I cann't start the service, It still show the Starting nfs service daemon is FAILED.
3)List out list of process which are used nfs service
# ps -ef | grep nfs
root 13282 177 0 17:10 ? 00:00:00 [nfsd4]
root 13290 1 0 17:10 ? 00:00:00 [nfsd]
root 13291 1 0 17:10 ? 00:00:00 [nfsd]
root 13392 177 0 17:10 ? 00:00:00 [nfsiod]
4)Kill the service
#kill -9 13284
# kill -9 13282
Like wise I kill the all the process
5)Then restart the nfs service it was starting nfs service perfectly.
Then the client will get kickstart file through nfs service and installation was completed succefully.

Linux Diff Command Diff Vimdiff Gvimdiff

2011-04-12T03:38:00.000-07:00

diff it can be used to compare the Two files
vimdiff perform the diff using vim
gvimdiff Perform vimdiff and provide Graphical editor
diff -w file1 file2
-w ignore the white space
diff command it telling about
'<' -Mention First File word (or) character Located in the first file

'>' -Mention Second File Word (or) Character have extra word in the second file

"---" mention it will compare the same line for the two files.
< Installing setup-2.5.58-7.el5.noarch rhel5
---
> Installing setup-2.5.58-7.el5.noarch
We can also use the Vimdiff -> it is vim editor,
It will compare the two file using different colors and we can can compare the n no of files like,
#vimdiff file1 file2 file3
gvimdiff -Graphical vimdiff editor.
COMPARE DIRECTORY
test1,2,3 file are locate only under the /tmp/p1 these file are not persent under /tmp/p2
#diff /tmp/p1 /tmp/p2
Only in /tmp/p1: test1
Only in /tmp/p1: test2
Only in /tmp/p1: test3

Segmentation Fault Run Time Error | Trace Out Debugging Using gdb

2011-04-11T23:47:00.000-07:00

That computer Physical Memory managed by the OS. It has different segmentation,
It will used for the storing data,variables,text,garbage values,
when we try to access memory location if it outside, or not able to read/write, or due to security it is not allow to access due to that segmentation fault occur.
Segmentation fault. It is Run Time Error.
1)if we are not assign the pointer in the correct format. like,
char *s = "hello world";
*s = 'H';
Pointer it is read only data type.
Reason- Already Pointer assign hello world, then we can't overwrite the value,.
Here it is attempting to write the read -only data due to that we are facing Segmentation Fault.
2)int i;
scanf("%d",i);
printf("%d",i);
return(0);
it will also generate Segmentation Fault Error.
Main Reason
1)rarely Compute Hardware is broken,
2)Bug in the program Source Code.
3)It can also appear when you try to access an array beyond the end of an array under C programming.
We can trace out these error using gdb command | Debugging Segmentation Fault

gdb- GNU Project Debugger

How to Run the Program under gdb
# gdb segfault
GNU gdb Fedora (6.8-37.el5)
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "i386-redhat-linux-gnu"...
(gdb) run >>Run The Program Under gdb
Starting program: /root/cprogrm/segfault
Program received signal SIGSEGV, Segmentation fault.
0x0804836f in main () at one.c:4
4 *s = 'H';
(gdb) backtrace
#0 0x0804836f in main () at one.c:4
These Type Error Will occur in C Programming, Vasp Programming when user give Large Matrix in Poscar file Input,Debugging Segmentation Fault

Smatrcl Check Harddisk Drive Health Condition

2011-04-11T05:01:00.000-07:00

Using smartctl command we can check the hard disk whether It is going to bad or not,it is self-monitoring tool, used to detect the reliability of the hard disk.
1)Fist we need to enable the smartctl.
-s value [ -s option is used to enable or disable hard disk]
# smartctl -s on -data /dev/hdc
smartctl version 5.38 [i686-redhat-linux-gnu] Copyright (C) 2002-8 Bruce Allen
Home page is http://smartmontools.sourceforge.net/
=== START OF ENABLE/DISABLE COMMANDS SECTION ===
SMART Enabled.
-d is used to specified the type.
ata, scsi, marvell, sat, 3ware,
# smartctl -d ata -H /dev/hdc
smartctl version 5.38 [i686-redhat-linux-gnu] Copyright (C) 2002-8 Bruce Allen
Home page is http://smartmontools.sourceforge.net/
=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED
If the hard disk health is good condition then we will get result :PASSED.
or we will get Failed

Pbsnodes Error Message Cannot resolve default server host

2011-04-07T00:15:00.000-07:00

After I installed torque whenever I tried pbsnodes I got the the following error message
#pbsnodes

Cannot resolve default server host 'master.rhel5.com' - check server_name file.

pbsnodes: cannot connect to server master.rhel5.com, error=15008 (Access from host not allowed, or unknown host)

(or)

Cannot connect to default server host 'master.rhel5.com' - check pbs_server daemon.

pbsnodes: cannot connect to server master.nice.com, error=111 (Connection refused)

change the /etc/sysconfig/network change the hostname

PROBLEM

while Installed and configured pbs torque in the /var/spool/torque/server_name we will add there
server name For here I entered the wrong server Host name.
SOLUTION
we need to confirm whether Master Server Host name and /var/spool/torque/server_name both are same or not.It is not same then we need maintain the same host name for server and /var/spool/troque/server_name, then check it the problem has been resolved.
NOTE: we need to maintain the same Host name in /var/spool/torque/server_name for node (client system) also. Error Message :Cannot resolve default server host 'master.rhel5.com' - check server_name file.
pbsnodes: cannot connect to server master.rhel5.com, error=15008 (Access from host not allowed, or unknown host)
(or)
Cannot connect to default server host 'master.rhel5.com' - check pbs_server daemon.
pbsnodes: cannot connect to server master.nice.com, error=111 (Connection refused)
change the /etc/sysconfig/network change the hostname

Ganglia Error Message gmond dead but subsys locked

2011-04-06T04:30:00.000-07:00

After I installed ganglia, I restart the gmond service.
it is restart perfectly, But while I check the gmond status,
I got the following error message.

PROBLEM

[root@node6 ~]# /etc/init.d/gmond status
gmond dead but subsys locked
SOLUTION
As per the Ganglia manual document, They suggest we need to add the route 239.2.11.71 for ethernet, try the following command then check it,
#route add -host 239.2.11.71 eth0
To add permanently we need to add the line to the following file
/etc/sysconfig/network-scripts/ifup-route - restart system and service then check it,# /etc/init.d/gmond status
gmond (pid 5243) is running... Error message :gmond dead but subsys locked

pbs_mom Is Not Running On The Node

2011-04-05T21:12:00.000-07:00

After Install the torque. I try to restart the pbs service then I check the pbs status.
[root@node2 ~]# /etc/init.d/pbs status
pbs_mom is not running
So Once again I try to restart the service While restarting I didn't get any error message.But it is not starting the pbs service properly.
[root@node2 ~]# /etc/init.d/pbs restart
Restarting PBS
Stopping PBS
Starting PBS
PBS mom

PROBLEM

[root@node2 ~]# /etc/init.d/pbs status
pbs_mom is not running

SOLUTION

ADD the correct host name for /etc/sysconfig/network file
HOSTNAME=compute.rhel5.com
Restart the system then restart pbs service then check it the problem Has been resolved.Error: pbs_mom is not running at the node.

givm Xlib connection to refused by server Xlib No protocol spectified

2011-04-05T20:47:00.000-07:00

while trying gvim command from the root user it will open that graphical with vim editor,But when we try non-root user I can't open the gvim editor.
#gvim filename.txt

Xlib: connection to ":0.0" refused by server

Xlib: No protocol specified

E233: cannot open displayXlib: connection to ":0.0" refused by server

Xlib: No protocol specified

PROBLEM
user try gvim command it will try to access X (Graphical) server.But That connection is refused by server
SOLUTION
Add the standard user ( non root user) to the xhost server
# xhost
access control enabled, only authorized clients can connect
SI:localuser:root
Default the gvim editor is enable only for the root user. To enable the non root user.
standard user. we have to run the following command.
xhost +local:username
#xhost +local:user2
Then try it gvim graphical vim editor it will open for the standard user.
Error:Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified
E233: cannot open displayXlib: connection to ":0.0" refused by server
Xlib: No protocol specified

PXE OS Error Message Is Not PXE Operating System

2011-03-31T00:39:00.001-07:00

when I was creating the Pxeos I got the following error message.
Pxeos Error message
While creating pxeos

You must enter directory of the Operating System Software

This directory must include the images/pxeboot directories

Error Mounting: mount: no such partition found

while pxeboot

linux(imagename) is not PXE Operating System

when we want to install the client Operating system from the server using kickstart method,we need to create the pxeboot, while creating it is not created perfeclty.I got the following error message.

ERROR MESSAGE

pxeos -a -i "$OS_IDENTIFIER" -p NFS -D O-s $IPADDR -L /export/$IMAGE_NAME $IMAGE_NAME
You must enter directory of the Operating System Software
This directory must include the images/pxeboot directories
Error Mounting: mount: no such partition found
pxeboot -a -O "$IMAGE_NAME" -K nfs:$IPADDR:/export/$IMAGE_NAME/kshclhpc2.cfg -r 10000 $PXE_NTWK
linux is not PXE Operating System
Check the NFS service whether It is booting perfeclty or not.

PROBLEM

1)check the image contain the image/pxeboot directory with following 4 files
a)initrd.img b)README c)TRANS.TBL d)vmlinuz
2)Or check the NFS Service status

SOLUTION:

1)if you face the first problem copy the DVD content files correctly
2)For second one,
try to restart the nfs service.
a)try to Restart NFS Service, if you face any problem in NFS Service
try the following link NFS ERROR MESSAGE (or) check the the server IP/subnetmask configuration.
b)If NFS is restarted perfectly try the following command
#exportfs -> it should show the mounted directory for pxeos Image.
Then try it your problem will be solved.
imagename is not PXE Operating System

Qsub Error Message Specified Queue | MSG=cannot locate queue

2011-03-31T00:19:00.000-07:00

qsub: No default queue specified MSG=cannot locate queue
While Installating torque we need to create the default queue
using qmgr command- if we didn't create the default queue for torque Resource Manager then it will through Following error message.
Error Message
qsub: No default queue specified MSG=cannot locate queue.

PROBLEM

TORQUE Resource Management queue not specified.

SOLUTION

we need to specified torque pbs queue using qmgr command.
How To Create The Qsub Queue
qmgr it is bps management system.
qmgr -c it is used to execute the single command.
So run the following command

qmgr -c "set server scheduling=true"
qmgr -c "create queue batch queue_type=execution"
qmgr -c "set queue batch started=true"
qmgr -c "set queue batch enabled=true"
qmgr -c "set queue batch resources_default.nodes=1"
qmgr -c "set queue batch resources_default.walltime=3600"
qmgr -c "set server default_queue=batch"
qmgr -c "set server operators += TORQUEADMIN@SERVERNAME"
qmgr -c "set server managers += TORQUEADMIN@SERVERNAM
Once queue created successfully you need list out that object Using the following command.
$qmgr -c 'p s'
create queue batch
set queue batch queue_type = Execution
set queue batch resources_default.nodes = 1
set queue batch resources_default.walltime = 01:00:00
set queue batch enabled = True
set queue batch started = True
# Set server attributes.
set server scheduling = True
set server acl_hosts = master.iitk.ac.in
set server default_queue = batch
set server log_events = 511
set server mail_from = adm
set server scheduler_iteration = 600
set server node_check_rate = 150
set server tcp_timeout = 6
set server next_job_number = 64
then you can submit the job
$qsub test.sh
To Check the job status - try the following command
$qstat & $qstat -q
qsub: Bad UID for job execution MSG=root user root not allowed- login as user then try it,
qsub: No default queue specified MSG=cannot locate queue.

Pxeos How To Create pxeos Operating System For Net boot

2011-03-28T23:18:00.000-07:00

pxeos - pxeboot configuration utility, When we try to install the Client Operating system through nfs,http,ftp,before going to install we need to create the pxeos.
SAMPLE EXAMPLE
#pxeos -a -i "<description>" -p <nfs|http|ftp> -D 0 -s client.example.com -L <net-location>
-k <kernel> -K <kickstart>
# pxeos -a -i rhel5.6 -p NFS -D 0 -s 10.1.1.1 -L /export/rhel5.5/ rhel5.5
Important Pxeos Option
-a — add OS to PXE configuration.
-i " <description> " — Replace " <description> "description of OS Image.
-p <nfs|http|ftp> — mention the service NFS | HTTP | FTP which one is used for the installation.
D <0|1> — Specify "0" refers to the it is not a diskless configuration.
-s client.example.com (OR) -s 10.1.1.1 — Provide the name of the NFS, FTP, or HTTP server after the -s option.
-L <net-location> — Indicate the Location of DVD Content Document,
-k <kernel> — Specify the kernel file
-K <kickstart> — specify kickstart file.(kshclhpc2.cfg)
<os-identifier> — Specify th
Once Pxeos created To list out pxe os
#pxeos -l
rhel5.7
Description:    rhel5.6
Protocol:       NFS
isDiskless:     False
Server:         10.1.1.1
Location:       /export/rhel5.5
pxeos configuration utility
/usr/sbin/pxeos
/tftpboot/linux-install/pxelinux.cfg/pxeos.xml
/usr/share/system-config-netboot/
system-config-netboot -< it will load network booting tool graphically.
Pxeos Error message
pxeos -a -i "$OS_IDENTIFIER" -p NFS -D O-s $IPADDR -L /export/$IMAGE_NAME $IMAGE_NAME
You must enter directory of the Operating System Software
This directory must include the images/pxeboot directories
Error Mounting: mount: no such partition found
pxeboot -a -O "$IMAGE_NAME" -K nfs:$IPADDR:/export/$IMAGE_NAME/kshclhpc2.cfg -r 10000 $PXE_NTWK
linux is not PXE Operating System
Check the NFS service whether It is start NFS service perfectly or not while booting.

Linux Important File Type Extension .so .a .f .c .rpm .py .sh .o

2011-03-22T02:18:00.000-07:00

.f file extensions
[root@jkumar GotoBLAS2]# file ftest.f
ftest.f: ASCII C program text
.h file extension
# file common_linux.h >> Header file
.so file extension

so Shared Object Files.
.so - FORTRAN 90 shared object
.so - Apache module file
.so - Executable and linkable format file
1)The Executable and Linking Format (ELF, formerly called Extensible Linking Format) it is standard file format for Object code,Shared Libraries, executable and core dumps.
2)ELF it is flexible and extensible
3)These is not any platform depented.
4)it will adopt to any Operating system.

.o for object files,
.a for shared object files
.py python shell script executable.
.sh Shell script.
.rpm red hat Package Manager
.conf configuration file

ls -l Command De pants upon the First character Output we can find out the file type.
l -symbolic link
d -directory
b - block-type special file
S - socket
c - character-type special file
p - named pipe

Ssh Login Error Connect To Host IP port 22: Connection Refused

2011-03-21T02:00:00.000-07:00

While I try to connect the 10.0.0.1 using ssh I got the following error message
1)ssh 10.0.0.1

ssh: connect to host 10.0.1 port 22: Connection refused

But it is ping to that ip with out any issue. But
while I try to connect i can't login with ssh it through error message.
because 10.0.0.1 /etc/init.d/sshd stop
so I try to restart
2)[root@localhost ~]# /etc/init.d/sshd restart
Stopping sshd: [FAILED]
Starting sshd: /var/empty/sshd must be owned by root and not group or
world-writable.[FAILED]

3)[root@localhost ~]# ll /var/empty/sshd
total 8
drwxr-xr-x 2 rhel5 rhel5 4096 Feb 4 08:40 etc
/var/empty/sshd it should be owned by root
problem /var/empty/sshd not owner of the root user
4)[root@localhost ~]# chown root:root /var/empty/sshd
So change the ownership permission to the root-
Then I try it,It is resolved, I can connect from the master.
[root@localhost ~]# /etc/init.d/sshd restart
Stopping sshd: [FAILED]
Starting sshd: [ OK ]ssh: connect to host 10.0.1 port 22: Connection refused

How To Install Java In Linux Redhat Firefox Plugin Addon

2011-03-10T21:45:00.000-08:00

To Install Firefox in Linux system Close Firefox and open terminal
1)[root@browser plugins]# locate libnpjp2.so
/usr/java/jre1.6.0_24/lib/i386/libnpjp2.so
if these library package is not available go to the following link
http://www.java.com/en/download/linux_manual.jsp
Download and install the package.
then you will get that library package.
Create the Soft link from the java library package to Firefox plugin,
2)ln -s /usr/java/jre1.6.0_24/lib/i386/libnpjp2.so /usr/lib/mozilla/plugins/

3)file libnpjp2.so

libnpjp2.so: symbolic link to `/usr/java/jre1.6.0_24/lib/i386/libnpjp2.so
4)Go to the following link For To Verify Java Installed or not.
http://www.java.com/en/download/installed.jsp
5)it will verify whether current browser has been installed java or not if install mean
you will get message like, "Congratulations!
You have the recommended Java installed (Version 6 Update 24)." or it will still loading that rotating icon.

How To set alias Command Permanently /etc/bashrc

2011-03-02T23:54:00.000-08:00

To work in the Linux user friendly or simplify work.
1)we can use Linux Shortcut.
2)create alias setting
3)write basic Shell scripting
4)set Environmental Variable.

Create Alias Command bashrc
If we are using any frequent command we can use use these option.
1)For example Frequently I go the Download Directory.
cd /tmp/Download. So I create the Alias setting for these
2)alias dwd="cd /tmp/Download" under >> /etc/bashrc
if we add these line to /etc/bashrc any user can use these setting
if it is ~/bashrc only the specified user only can only use that alias.
3)after add that line we need to restart the system to update bash.
But it will take the time. To save these time in there terminal type the command
#bash
4)Then open the terminal and try it.

Monitor Screen Resolution Problem Attention Out of range Screen Resolution Error message

2011-03-02T23:46:00.000-08:00

In Linux Operating System. I change Desktop Screen Resolution.
#system-config-display or System>Administor>Display.
Here I change the Screen Resolution Display From 800*600 To 640 * 480.
While I fire the Ok Button I got the message box with
"Display settings changed

You need to log out and restart the X server for the changes to take effect.

Configuration was written to /etc/X11/xorg.conf, original configuration saved as /etc/X11/xorg.conf.backup."
PROBLEM:
After I restart the System while starting the Graphical window I got the following error message.
Attention
Out of range
H:106.1KHz V:84.9Hz
SOLUTION:
1)After I restart the system the modified screen resolution 640*480 it does not support monitor.So that I got the error message "Attention Out of range".
2)Then I go the directory /etc/X11.
3)Here System main take the backup copy of the old screen resolution configuration file form /etc/X11/xorg.conf to /etc/X11/xorg.conf.bakp
4)I rename backup file #mv /etc/X11/xorg.conf.backup /etc/X11/xorg.conf
5)Restart the system Then try it The problem will be resolve. If you still face the problem go to the #system-config-display or System>Administor>Display. and change to the old setting.

Hot To Set Environmental Variable In Different Bash C Shell

2011-03-02T01:45:00.000-08:00

Environmental Variable Seting it will differ depends upon the Bash,
How to find the Current Shell
#cat /etc/passwd | grep accelrys
accelrys:x:504:504:Accelrys Inc:/home/accelrys:/bin/csh
Shell is Command Line Interpreter.
Most of Linux/Unix Shell Have Bourne Shell and C Shell.
[root@master home]# cat /etc/passwd | grep root
root:x:0:0:root:/root:/bin/bash or
[root@master home]# echo $SHELL

/bin/bash

[accelrys@master ~]$ echo $SHELL

/bin/csh

Set Environment Variable
export VARIABLE=value # for Bourne, bash, and related shells
setenv VARIABLE value # for csh and related shells
set VARIABLE=value //DOS on Windows
C:\> set p
Path=c:\.. ..
PATHEXT=.COM;.EXE;.BAT;
c:\>echo %VARIABLE%

In the all the LInux system PATH it has already variable, Now I will add some other append variable.
#export PATH=$PATH:/home/rhel5/
[root@jkumar ~]# echo $PATH
/usr/lib/qt-3.3/bin:/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin:/root/bin:/home/rhel5
we can also add through bash_profile.
export dwd=/home/username/download/ add these line to $HOME/.bash_profile
Save and exit
Set Environmental Variable In Different Shell

Http Server Error Message Exception KeyError Unable To Change Directory

2011-03-02T00:44:00.000-08:00

After I configure http service.While I restart the service.
I got the following error message.
[root@rhel6 ~]# /etc/init.d/httpd start
Starting httpd: [FAILED]
1)read the log file
2)#cat /var/log/httpd/error_log | grep error
) in ignored
[Thu Feb 24 12:20:19 2011] [error] Exception KeyError: KeyError(140472509999072,) in ignored
[Thu Feb 24 12:20:19 2011] [error] Exception KeyError: KeyError(140472509999072,) in ignored
PROBLEM
Unable to find the python script
SOLUTION
1)create the Soft link for the python script
#ln -s /usr/local/lib/libpython2.6.so.1.0 /usr/lib64/libpython2.6.so.1.0
#ln -s /usr/local/bin/python2.6 /usr/bin/python2.6
Then try it, if you still face the error message.
Read the log message

2)#cat /var/log/httpd/error_log | grep error
ERROR MESSAGE
[Thu Feb 24 12:20:20 2011] [error] Unable to change directory to /root
SOLUTION
In these case /root is Present Working Directory PWD.
change the present working directory then try it.
Depend upon the log message we need to clear the problem.

Install Package With Configure Make Make Install .tgz Command

2011-02-24T21:51:00.000-08:00

Most of Linux Open Source Software Package come with .tgz tarball format.
These Packages install with three command
1)./configure
2)make
3)make install

./configure

a)configure it is just shell script
b)configure it check lot of dependency on the current system.
c)output it has short question with [YES/NO] answer.
d)if any of the major requirement is missing then it will not continue.
e)if it is fulfill there requirement,Then
it will build new Make file.

SAMPLE CONFIGURE OUTPUT

checking for memory.h... yes
checking whether struct hostent contains h_addr_list... yes
checking that we can build MPI programs with Fortran 77... no

MAKE

while we run the make command first it is look for makefile then it will build there program as per makefile instruction,
if the make run successfully, then it is almost finish.

MAKE INSTALL

it will find the Install in the makefile.
when run make command without any parameter makefile begin from the start.
But when we run make with Install Parameter then make it will search the label install in the file and run only that section. In these process it will copy some of the binary file to the /usr/local/bin so that all the user can run that command.

Configure With Different Option
./configure --with-fc=0
If we want to disable some Feature like fortran compiler
./configure --with-fc=0 Disable the Fortran complier
./configure --with-mpi=0 Disable MPI
./configure --help
./configure --prefix=Installation Directory Path
./configure CC=gcc Setting the Environment Variable
./configure --enable-application= we can enable the application - browser,mail,calendar,mail,
./configure --includedir=DIR [ Include the C Header Files ]

How To Check Whether Tar backup Differ From the Original Source File Or Not

2011-02-23T01:22:00.000-08:00

Using tar -df option we can find out the difference between tar backup and the original Source files. And we can check whether tar it take Backup complete or not.
it will check size,time,file present or not
Sample Output

size is differ

Mod time differs

Not found in archive >> backup.tar doesn't contain the file
No such file or directory >> backup.tar file it has file but not persent in source file
Syntax
#tar -dvf Backup.tar sourceDirectory*
#tar -dvf rhel5.tar rhel5/*
-d Difference
-v verbose
-f user Archive.
1)Our present working directory it should be current directory of source file
Example
#tar -dvf home.tar home/*
#tar -dvf /root/home.tar home/*>> These are Correct

2)Here we Don't Give Like That | Wrong Syntax
#tar -dvf /root/home.tar /home/*
Original Source Document it does not come with '/' like /root/home* (or) /home*
Example if the original source file is /root/rhel5 mean
our pwd should be /root/
Because while compress file it compress like
[root@master /]# tar -df home1.tar
home/
home/indraveer/
home/indraveer/.login.old
home/indraveer/.profile.old
it compress like.

3)#tar -tf backup.tar >> list the achieve files
4) How to exract the tar file to the particular Location
#tar -xvf scartch.bak -C /
#tar -xvf Sourcefile.tar -C DestinationDirectory
-C change Destination Directory

Linux Folder Chkconfig Add Service Ubuntu Change Root Password Tee command

2011-02-22T20:43:00.000-08:00

Linux How to Open the folder IN the Same Window
Default Linux setting whenever we open the Folder it will open the New Folder.So it will increase the no of windows in the Desktop.it will create the Lot of complex to work.
To Make it user friendly.

1)Open the folder>
Edit>preference>Behavior>Always Open in Browser Windows.

2) How to add New service to chkconfig
#chkconfig --add ServiceName
Example
#chkconfig --add pbs

3) For Ubuntu version How to login to to the root
Actually All the Ubuntu version root is not enable using sudo command we can do the all the root Super User privilege.
#sudo command
#sudo passwd root
Using the above command we can update the ubuntu root password.

4)ls | tee ls.log
It will list out files and directory at the same time it will write to the output to the
ls.log file.

Login Remote System ssh Without Password | Linux Redhat Rhel5

2011-02-17T04:35:00.000-08:00

First we need to create rsa Key
1)#ssh-keygen -t rsa
-t rsa it will create the RSA(Rivest, Shamir and Adleman) Key
it will creat the key with file name "id_rsa.pub" under the current user Home Directory.
If it is root mean /root/.ssh/id_rsa.pub
if it is redhat mean /home/redhat/.ssh/id_rsa.pub
ssh-copy-id it will install public key to the remote machine
then copy the id to the remote system, For first time it will ask the password.
Next it will not ask the password.
#ssy-copy-id -i /root/.ssh/id_rsa.pub remoteuser@remoteip
2)#ssh-copy-id -i /root/.ssh/id_rsa.pub hpc@151.8.27.214
While Copy the key it will ask the Password For enter the Login credentials.
AFter copy completed.
3)then try to login from the remote sytem. It doesn't ask any of the password.

VNCVIEWER Error Message: vncviewer unable to open display

2011-01-31T21:24:00.000-08:00

I try to connect Remote system(GUI- Remote Desktop) through ssh for that Purpose I used VNC.
VNC - Virtual Network Computing,Remotely control another Computer Like Remote Desktop.
It is used to Trouble shooting the problem.While I try
[root@remote ~]# ssh 151.8.19.140
Last login: Tue Feb 1 15:47:03 2011 from 151.8.19.145
[root@ha2 ~]# vncserver
New 'ha2.hcl.in:5 (root)' desktop is ha2.hcl.in:5
Starting applications specified in /root/.vnc/xstartup
Log file is /root/.vnc/ha2.hcl.in:5.log
[root@ha2 ~]# vncviewer :5
VNC Viewer Free Edition 4.1.2 for X - built Jan 26 2009 11:52:08
Copyright (C) 2002-2005 RealVNC Ltd.
See http://www.realvnc.com for information on VNC.
vncviewer: unable to open display "

ERROR MESSAGE

vncviewer: unable to open display

PROBLEM

while Login through ssh we Didn't enable the X11.
X11 refers to the GUI - Graphical User Interface
SOLUTION
while login though ssh use the option '-X' To enable X11.
-X enable X11
-x Disable X11.
Then it will work
[root@remote ~]# ssh -X 151.8.19.141
Last login: Tue Feb 1 10:18:55 2011 from 151.8.18.160
[root@ha1 ~]# vncserver
New 'ha1.hcl.in:4 (root)' desktop is ha1.hcl.in:4
Starting applications specified in /root/.vnc/xstartup
Log file is /root/.vnc/ha1.hcl.in:4.log
[root@ha1 ~]# vncviewer :4
VNC Viewer Free Edition 4.1.2 for X - built Jan 26 2009 11:52:08
Copyright (C) 2002-2005 RealVNC Ltd.
See http://www.realvnc.com for information on VNC.
Tue Feb 1 10:19:26 2011
CConn: connected to host localhost port 5904
CConnection: Server supports RFB protocol version 3.8
CConnection: Using RFB protocol version 3.8
Then I got the Graphical Window For the Remote System.

Create New File System To New Partition No such file or directory

2011-01-31T20:13:00.000-08:00

I create the New Partition under /dev/sda sata Hard disk(dev/sda3). After create the the partition using fdisk then while I create the file system using mkfs.ext3 command I got the following error message.
[root@node2 ~]# mkfs.ext3 /dev/sda3
mke2fs 1.39 (29-May-2006)
Could not stat /dev/sda3 --- No such file or directory
The device apparently does not exist; did you specify it correctly?
I try to mount with the following command
[root@node1 ~]# mount -t ext3 /dev/sda3 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/sda3,
missing codepage or other error
(aren't you trying to mount an extended partition,
instead of some logical partition inside?)
In some cases useful info is found in syslog - try
dmesg | tail or so

PROBLEM

Linux Operating System It does not find the New Partition from the Hard Disk.
SOLUTIONActually From the resource they suggest me to restart the Operating System But, It will take time,
We can Avoid To restart the Server using
#partprobe using these command we can Update the partition Table.
So Linux Kernel it can find the New Partition.
Then we can create the file system with out reboot the system.
HereAfter Using mkfs command we can create the file system.
[root@node1 /]# partprobe
[root@node1 /]# mkfs.ext3 /dev/sdb2
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
36519936 inodes, 73021449 blocks
3651072 blocks (5.00%) reserved for the super user
...............
ERROR MESSAGE
#mount /dev/sdb2 /mnt
After Mounting check using #df -T check whethere file system is created perfectly or Not.
#df -T
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/sdb1 ext3 36904824 7261744 27738176 1% /mnt
[root@node2 ~]# mkfs.ext3 /dev/sda3
mke2fs 1.39 (29-May-2006)
Could not stat /dev/sda3 --- No such file or directory
The device apparently does not exist; did you specify it correctly?
I try to mount with the following command
[root@node1 ~]# mount -t ext3 /dev/sda3 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/sda3,
missing codepage or other error
(aren't you trying to mount an extended partition,
instead of some logical partition inside?)
In some cases useful info is found in syslog - try
dmesg | tail or so

SSH Login Error Message: MANPATH: Undefined variable man.csh

2011-01-24T20:49:00.000-08:00

Server, When I Login From the Master to the client Node.
I got the following error message.d
[redhat5@master ~]$ ssh node6
Last login: Tue Jan 25 11:45:11 2011 from node1.modeling.in
MANPATH: Undefined variable.
[redhat5@node6 ~]$
Reason
MANPATH VARAIBLE is declare but these value is not assign.
SOLUTION
So create the man.csh file under the /etc/profile
csh refers to the C ShellSSH Login Error Message
#/etc/profile.d/man.csh
cat man.csh
if ($?MANPATH) then
setenv MANPATH "${MANPATH}:/usr/man"
else
setenv MANPATH "/usr/man"
endif
setenv command is used to set environment variable.
After create the file then again try it.
It will work perfectly.MANPATH: Undefined variable.

Useful Linux KeyBoard Shortcut Hot Keys

2011-01-23T21:49:00.000-08:00

1)ctrl+c -> kill the current process
2)ctrl+z -> kill the process to the background
3)ctrl+d -> Log out the current terminal
4)~ (tidle) refer to the home directory
cd ~/Desktop/
5)alt+f1 Access the K-menu (k-menu similar to star button in windows)
6)alt+print screen take the screen shot only to the current window
7)print Screen Take the snapshot for the entire window
8)ctrl+u - Delete the whole statement
9)ctrl+w - Delete the single word
10)ctrl+t - Swap the last two character
11)Alt+u - Make the Upper Case
12)Alt+l - Make the Lower Case
13)ctrl+atl+l - Lock the Desktop

#dateconfig (or) system-con fig-date
#hwbrowser Give the Graphical window for Hardware Details
1 Byte = 8 Bit
1 Kilobyte = 1024 Bytes
1 Megabyte = 1048576 Bytes
1 Gigabyte = 1073741824 Bytes
Red hat Fedora Scientific Linux Keyboard Shortcut or Hot Keys.

Restore Recreate Lost MBR Grub Boot Loader Linux

2011-01-21T00:39:00.000-08:00

Problem - lost grub.conf & MBR Master Boot Record
In my system due to unclean shutdown, grub.conf and mbr are corrupted.So when I restart the system it is going to the grub window.I restart the Operating system using rescue mode.
After I loading we need to do the following things
SOLUTION Restore MBR grub loader
1)Find where the grub.conf file are located.
grub> find /boot/grub/stage1
(hd0,0)
2)Find the File system of the root partition
grub> root (hd0,0)
File system type is ext2fs, partition type 0x83
3)using setup command install grub.conf file
grub> setup (hd0)
Checking if "/boot/grub/stage1" exists... yes
Checking if "/boot/grub/stage2" exists... yes
Checking if "/boot/grub/e2fs_stage1_5" exists... yes
Running "embed /boot/grub/e2fs_stage1_5 (hd0,0)"... failed (this is not fatal)
Running "embed /boot/grub/e2fs_stage1_5 (hd0,0)"... failed (this is not fatal)
Running "install /boot/grub/stage1 (hd0,0) /boot/grub/stage2 p /boot/grub/grub.conf "... succeeded
Done.
NOTE:if boot Parition is present in root (hd0,5) then we have to install like
setup (hd0) that is correct method setup. Because it will install in to the mbr of hard disk 0. (hd0,5) it is Not correct one.Because we can't give any gurantee it will install into the mbr of hd0.
4)Now load the kernel and initrd
grub> kernel /boot/vmlinuz-2.6.18-164.el5 ro root=LABEL=/ rhgb quiet
[Linux-bzImage, setup=0x1e00, size=0x1c31b4]
grub> initrd /boot/vmlinuz-2.6.18-164.el5
Possible files are: vmlinuz-2.6.18-164.el5 vmlinuz-2.6.18-164.el5xen
There initrd these boot loader initialized a ram disk.
Finally type the #boot command it will boot your operating system.

Restore Grub trouble shooting related command
fsck.ext3 /dev/hda1 >>check the file system.
grub-install --root-directory=/mnt /dev/hda1 >> install grub boot loader
chroot /mnt/sysimage >> it will change the default root directory to /mnt/sysimage
mount -t ext2 /dev/hda2 /mnt/sysimage >> if hardisk unable to mount we can using these command
Login to the resuce mode for Linux redhat centos fedora to resolve the grub and mbr corrupted file.
grub> find /boot/grub/stage4
Error 15: File not found
if you get Error 15 File not found Then try with following command
grub> find (hd0,0)/boot/grub/stage1
(hd0,0)
grub>root (hd0,0)
grub>setup (hd0,0)
Error 15: File not found
grub>kernel (hd0,X)/boot/
/dev/sda1 will be hda(0,0)
/dev/sda2 will be hda(0,1)
/dev/sdb1 will be hda(1,0)
/dev/sdb2 will be hda(1,1).Error 15: File not found

How To Run Teamviewer Under Root User | exec: /opt/teamviewer/teamviewer//bin/wrapper:

2011-01-20T02:23:00.000-08:00

while run team viewer From the root User I got the following error message
Team Viewer must not be executed as root! or team viewer will not open.
Actual team viewer shell script they write the shell script if we execute team viewer from the root user [ root user id=0 ] display the error message or it will not open. shell script located under /usr/bin/teamviewer
[root@rhel5 bin]# cat teamviewer

#!/bin/sh

userid=$(id -u)

tv_ver="6"

if [ $userid = 0 ] # root user id is 0

then

echo TeamViewer must not be executed as root!

exit 1

Here from the other resource they suggest to disable the line like adding Hash symbol # ,make the command line . From
Line: userid=$(id -u) to
Line: fi/usr/bin/teamviewer: line 13: /opt/teamviewer/teamviewer//bin/wrapper: No such file or directory
/usr/bin/teamviewer: line 13: exec: /opt/teamviewer/teamviewer//bin/wrapper: cannot execute: No such file or directory

SOLUTION

It is better I will suggest just edit the uid is equal to 12 instead of 0 then try it you will get the team viewer even though if you are root user.
[user id 12 is the system user so it will not affect you any more].
/usr/bin/teamviewer: line 13: /opt/teamviewer/teamviewer//bin/wrapper: No such file or directory
/usr/bin/teamviewer: line 13: exec: /opt/teamviewer/teamviewer//bin/wrapper: cannot execute: No such file or directory

NFS ERROR: NFS Server Hostname failed:RPC Error: Program not registered

2011-01-20T01:58:00.000-08:00

server I configured with NFS.
/etc/export file I add the entry what are directories need to mount
In the client /etc/fstab add the entry to mount directory from server to client
IN THE CLIENT
While I try with #mount command To check what are things are mounted.
server shared directory it is not mounted to the client. So I try to remount
#mount -a it will mount directory according to the /etc/fstab file
while I try thes I got the following error message

mount: mount to NFS server '128.150.72.58' failed: RPC Error: Program not registered

I check in the server whether rpc support nfs. Because rpc - Remote Procedure Call is required share nfs File System.
TROUBLESHOOTING ISSUE
1)rpcinfo -p
[root@master1 ~]# rpcinfo -p [ it will show portnumber what are thing related to rpc]
program vers proto port
100000 2 tcp 111 portmapper
100000 2 udp 111 portmapper
100024 1 udp 1006 status
100024 1 tcp 1009 status
100011 1 udp 739 rquotad
100011 2 udp 739 rquotad
100011 1 tcp 742 rquotad
100011 2 tcp 742 rquotad
100021 1 udp 54266 nlockmgr
100021 3 udp 54266 nlockmgr
100021 4 udp 54266 nlockmgr
100021 1 tcp 58009 nlockmgr
100021 3 tcp 58009 nlockmgr
100021 4 tcp 58009 nlockmgr
100005 1 udp 813 mountd
100005 1 tcp 816 mountd
100005 2 udp 813 mountd
100005 2 tcp 816 mountd
100005 3 udp 813 mountd
100005 3 tcp 816 mountd
From these troubleshooting I found NFS it is not associated with RPC.
SOLUTION
So,I restart the NFS service.
In the first time NFS is not shutdown properly.
so, I restart it again. then I try it
[root@master1 ~]# rpcinfo -p | grep nfs
100003 2 udp 2049 nfs
100003 3 udp 2049 nfs
100003 4 udp 2049 nfs
100003 2 tcp 2049 nfs
100003 3 tcp 2049 nfs
100003 4 tcp 2049 nfs
So Here I confirm RPC Provide service to nfs.
Then in the client again I try to remount it with mount -a option.
it is mounted perfectly with out any issue.Then the problem has been clearled.
Mount to NFS Server Hostname failed:RPC Error: Program not registered.

What last+found Directory in Linux Operating System | ext3 Corrupted or Damaged Files

2010-12-19T03:28:00.000-08:00

What is Purpose of last+found Directory.
1)last+found it will store corrupted or damage files when the unclean Power failure occur or system shutdown occur.
2)when we create the ext3 file system.
'lost+found' directory is created.
under these directory if any of the file has been damaged or crash the files will be store under 'lost+found'.
3)After the unclean or power failure of the system when the system boot it will check the fsck command
last+found Directory ext3 file system in Linux.
Whenever we create new file system under linux /Unix it will create lost+found directory,
it will be used for file system check & repair fsck utility In .
When the file system is mounted,
we can't used fsck command.
fsck it will check

Linux Swap Partition what is purpose of Swap parition

2010-12-14T15:29:00.000-08:00

Combine memory of physical memory and swap space it is amount of virtual memory .
Physical RAM- chunks of memory called pages.
Paging is one of the Memory-Management System.
1)Computer Can store and retrieve data from the Secondary Storage For use of Main Memory.
2)OS retrieve data from Secondary Storage in Same size block called Pages.

swapping is an area on disk temporarily hold process memory image.
swap space keeps some physical memory free at all the times.
Swapping it is required fro the following reason
1)Because the system requires more memory than physical memory.
2)significant number of pages used by an application using the startup process or bootup process. it will happen only the system startup process only for initialization. system can swap these pages and free memory for other application disk cache
using #swapon -s
command we can find out where is swap partition is installed.
#swapon -s
Filename Type Size Used Priority
/dev/sda2 partition 20774904 52 -

unable to umount device is busy use lsof fuser umount -l

2010-12-14T15:15:00.000-08:00

while we want to increase the partition size or remove the partition we try to umount the particular partition.In that time when we use umount the particular partition it is unable to umount we will get the message.
Device is busy.

For an example
#umount /dev/sda1
if we get anything unable to umount busy
umount: /: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
fuser identify process which are using the file and socket.
# fuser -m /dev/sda1
it will show the list of process which are things using these disk
/dev/sda1: 2400
1rce 2rc 3rc 4rc 5rc 6rc 7rc 8rc 9rc 10rc 11rc 12rc 13rc 14rc 15rc 16rc 17rc 18rc 19rc 20rc 21rc 22rc 23rc 25rc 26rc 27rc 28rc 29rc 30rc 36rc 37rc 39rc 41rc 44rc 45rc 46rc 47rc 48rc 49rc 233rc 234rc 235rc 236rc 309rc 310rc 351rc 380rce 384rce 524rce 526rc 545rce 587rc 594rc 601rc 702rc 837rce 848rce 859rce 860rce 866rce 870rce 871rce 881rce 883rce 953rce 978rce 1099rce 1234rce 1270re 1274re 1287re 1288re 1290re 1292rce 1294rce 1295rce 1343rce 1347rce 1368rce 1440e 1521re 1529rce 1548rce 1578rce 1581rce 1582rce 1587rce 1591rce 1596rce 1601rce 1606rce 1612rce 1614rce 1616rce 1617rce 1618rce 1619rce 1620rce 1622rce 1624rce 1625rce 1630rce 1636rce 1706rce 1723rce 1728rce 1729rce 1732rce 1734rce 1736rce 1752rce 1753rce 1754rce 1755rce 1756rce 1757rce 1768rce 1770rce 1773rce 1782rce 1794rce 1815rce 1848rce 1851rce 1852rce 1899rce 1946rce 1950rce 1954rce 2217rce 2274rce 2318rce 2374rce 2383rce 2400rce 2591rce 2592rce 2608rce 2617rce 2750rce 2773rce 2774rce 2845rce 2854rce 2862rce 2880rce 2901rce 2936rce 3250rc 3251rc

These device is using the above process.
#kill -9 pid
Using kill command kill that process what are process occupy that device.
then try it.
other wise we can use lazy umount command | -l refers to the lazy
#umount -l /dev/sda5
if you still face the problem
check whether that particular partition is used by the nfs.
If it is used by the nfs then just shutdown the nfs service.
Then try it. It will work.
[root@master ~]# /etc/init.d/nfs stop
Shutting down NFS mountd: [ OK ]
Shutting down NFS daemon: [ OK ]
Shutting down NFS quotas: [ OK ]
Shutting down NFS services: [ OK ]
[root@master ~]# umount /dev/sda5
lazy umount it will cleanup all reference of the file system and it is not busy any more.

How To Change Root Password Redhat Linux In Single User Mode

2010-12-11T11:42:00.000-08:00

1)While It shows booting option Kernel boot menu will appear.
click any single character it show the list of booting Os title
2)click ‘e’ charcet e means edit

Here it will show the there paramet root(hd0,0) and
2)kenel /boot/vmlinuz-2.6.18-53.el5 ro root=LABEL=/ rhgb quiet
3)initrd /boot/initrd-2.6.18-53.el5.img

Here choose the second kerenl option then add the word “single” at the end of the second option of the kernel
2)kenel /boot/vmlinuz-2.6.18-53.el5 ro root=LABEL=/ rhgb quiet single
After add the word press ‘b’ character it will boot theat kernal with single user mode
then enter it will boot as the single user mode.
here you can change the root password by typing #passwd command
After change the password#init 6 restart the linux system then try it.

Basic About ORACLE DATABASE control file redolog files Table Space DDL DML

2010-12-10T12:00:00.000-08:00

ORACLE DATABASE is a collection of data in a unit,
purpose of data is store and retrieve data,
To maintain the quality of the database server prevent unauthorized access and provides quality solution whenever unclean shutdown occur.

CONTROL FILES
control file it contain the physical information of the data.
all the oracle database contain the control files.it contain,
database name,timestamp,location,redlo files,
REDO LOG FILES
all the oracle database contain two or more redo log files.
set of redo log file called redo log database.
To prevent the failure redo log failure maintain the multiplexed redo log file.
so two or more copies of redo log maintain the different disk.
if unexcepted power failure occur by applying redo log file we can getback the database.
Logical Oralce Database Structure
Table space
database divided into the logical unit called table space.
Data Defination Language ( DDL )
create,alter,maintain,drop,
Maintain the permit a user to grant other user privilage to access database
Data Manipulation Language (DML)
insert,update,delete,select query retreive data from the databse,
Transcation Control Statements
Commit,rollback,savepoint,

How To Find The Parent Process Tree Directory Structure | Change The Process Priority

2010-12-10T11:37:00.000-08:00

By using Ps command we can find out the process id for the particular process.we can use to maintain the system in the proper manner. For example we are opening opera, but opera it is not opening, it will hang up the system, in these case we can find out the process id for the opera. and using kill command we can kill that particular process

#ps -ef | grep opera
rhel5 2190 1712 10 14:05 ? 00:00:03 /usr/lib/opera/opera
rhel5 2210 2190 21 14:05 ? 00:00:03 /usr/lib/opera//operapluginwrapper 52 69 /opt/mint-flashplugin/libflashplayer.so
rhel5 2211 2190 0 14:05 ? 00:00:00 /usr/lib/opera//operaplugincleaner 2190
rhel5 2231 2136 0 14:05 pts/1 00:00:00 grep --colour=auto opera
#kill -9 219
-f give the full details
-F give the Extra Full Details
Syntax
#ps U Username
[root@vps ~]#ps U mysql >> find out the particular user Details
PID TTY STAT TIME COMMAND
1109 ? Sl 757:51 /usr/sbin/mysqld --basedir=/ --datadir=/var/lib/mysql
How to find the Process Tree
ps -axf
x -proces w/o controlling tty
f-full
#ps -axf
15230 pts/0 Ss 0:00 | \_ -bash
15396 pts/0 T 0:00 | \_ mysql
28459 pts/0 T 0:00 | \_ mysql
5785 pts/0 T 0:00 | \_ mysql
8826 pts/0 T 0:00 | \_ mysql
17588 pts/0 T 0:00 | \_ find / -name init.d*
18777 pts/0 T 0:00 | \_ find / -name init.d
813 pts/0 T 0:00 | \_ find / -name eth0*

We can also get the process tree using pstree command
-p refers to the process id
#pstree -p
pstree - display a tree of process.
pstree parent of all the process is init.
How To find out the particular command process id
Using command find the Process id
# pidof ssh
2136
Using Process id find the Command
Method -1
ps -p 42 -o comm=
# ps -p 1154 -o comm=
wpa_supplicant
# ps -p 385 -o comm=
udevd
Method -2
#ps -ef | grep processid
How to renice the process priority

User Define Ps command display
#ps -o pid,command

How to fine parent child process> ptree pid
nice command
nice value vary from -20 to 20.
-20 Most Favorable scheduling(Highest)
19 Least Favourable scheduling (Lowest)
How to change the value
#nice -n 10 gmplayer
#renice -n
#/bin/nice -n 3 command-name
TO MORE ABOUT PS COMMAND
http://studentwebsite.blogspot.com/2009/10/how-to-use-ps-command-in-linux-rhel5.html

To see the Directory structure we can use the following command
#tree Directory name
#tree $HOME
#tree /
To Display the Directory with size
we can use the following command
#tree -s >> size
#tree -d >> direcotry
#tree -a >>hidden files
#tree -p >> along with files

Using Single Ethernet Device How To Configure Multiple Virtual IP

2010-12-10T11:12:00.000-08:00

How to configure Additional IP Address In Linux
In the LInux operating system using one Ethernet device we can create the multiple virtual ip
like that eth0:1,eth0:2,eth0:3,eth0:4
1)copy the file from
/etc/sysconfig/network-scripts/ifcfg-eth0 to ifcfg-eth0:1
2)change the Device name from
Device=eth0 to Device=eth0:1
3)/etc/sysconfig/network-scripts/ifcfg-eth0:1modify IPADDR
4)start the secondary interfaceifup eth0:1

Shell Script Login Remote System Using SSH Update Server Status

2010-11-23T13:38:00.000-08:00

By using shell script Login into the remote system using ssh and update there server status.I use the Important Linux command which one I used in the following shell script.

expect - maintain the interactive program.it will talk to other process via script. it is mainly used in the shell scripting to send the password & user name. These name come from send/expect.
expect >> wait for string from the process
send >> send the string to the process
while the interaction if expect get the string match with assword. it will send the password value.

expect \"*?assword:*\"
send -- \"$PASS\r\"

spawn >> start process

To write Bournce - Again Shell script To update the server details Using - expect -send -spwan command

#!/bin/bash
HOST="remote-hostname"
USER="remote-user"
PASS="remore-user-password"
CMD=$@
VAR=$(expect -c "
spawn ssh -o StrictHostKeyChecking=no $USER@$HOST $CMD
match_max 100000
expect \"*?assword:*\"
send -- \"$PASS\r\"
send -- \"\r\"
expect eof
")
echo "==============="
echo “shell script Output”l
echo $VAR
Run the Shell Script
#sh execute.sh 'exim -bpc'
How To use spawn command
spawn ssh -o StrictHostKeyChecking=no $USER@$HOST $CMD
-bash: spawn: command not found
spawn command start with expect or you will get the error message

Correct Format
expect -c “spawn ssh -o StrictHostKeyChecking=no $USER@$HOST $CMD”
Wrong Format
spawn ssh -o StrictHostKeyChecking=no $USER@$HOST $CMD”
-bash: spawn: command not found

Linux Important Command Service Important Step

2010-11-22T16:59:00.000-08:00

Open list of files particular protocol	lsof –i TCP,lsof –i TCP:80,
list of open file particular service,user	lsof –c http,user
Backup tar,gzip,bunzip2,cpio	tar –cvf backup.tar sourcefile file,bunizp2 sourcefile,find / -name *.c \| cpio –o –format=tar cfile.tar
RAID-3 , RAID -5	Parity separate disk, parity across disk
RAID -0,RAID -1	Striping , mirroring,
Iptables –chain –Accept-Reject-Drop, rules	-A,-s,-d,-p,-j,-i,
Log file,	/var/log/messages,/var/log/lastlog,dmesg
http log file	/var/log/httpd/error_log,/var/log/httpd/access_log
Shutdown option	Shutdown –r,-f,-h
Raid	Mdadm –c /dev/md0 –l1 –n2 –x1 /dev/had(1,2)
Zombie Process	Kills –S SIGCHILD [processed], ps –el \| grep ‘s’
/etc/passwd	Usernme:xyx:3:4:Commend:Home Directory:shell login
/etc/fstab	/dev/sda3 /mnt ext3 defaults 1 0 deviceName MountPoint FileSystem mount optiong dumb fsck order
Cut	Cut -d –f3,4 /etc/passwd
Booting option	BIOS –MBR-kernel-init-Run Level
Networkg monitor command	Netstat \| Routing table,masquerade connection, Netstat –r,netstat –an \| grep 80, Network statics netst -s
Difference Between ext2 to ext3 file system	Availablity, Data Integrity, Speed, Easy Transition
Ext2 to ext3 \| Ext3 to ext2	tune2fs –j /dev/hda1 \| #tune2fs –O ^has_journal /dev/hda10
Port Number SSH-IMPAS-mysql-smpts	22-993-3306-465-
/proc File system	Details about kernel,Hardware,Running process /proc/PID, mdstat,cpuinfo,meminfo,modules ,mount,partition
Kernel job	System initialization ,Memory Management, Network Management ,Security,
Userid ,groupid, stick bit	setuid: chmod 4000 setgid: chmod 2000 sticky bit : chmod 1777
Sudo	/etc/sudoers,visudo , [username] [system name] = [paths] restart rhel5 sys1.redhat.com=/etc/httpd/restart
vmstat	Monitor virtual memory Id-idle time wa –watingi for input Us-[user time] –time spending on kernel mode Sys-[sys time]-time spending on kernel mode
Umask	Root 022 user 002


SERVICES
/usr/share/doc/dhcp-3.0.5/dhcpd.conf.sample	subnet 192.168.0.0 netmask 255.255.255.0 { -- line 4 range dynamic-bootp 192.168.0.128 192.168.0.254; –line 21
Web Server	/var/www/html /etc/httpd/conf/httpd.conf
NIS	1)install yp* package 2)add the /etc/sysconfig/network NIS Domain=rhel5 3)portmap & ypserv restart 4)Add Host /usr/lib/yp/ypinit –m 5)Add the user 6)/var/yp ->make client Add the NIS domain using setup 3)
NFS	/etc/exports 2) restart 3)showmount –e ip
User quota	1)etc/fstab , usrquota , 2)mount –o remount /home 3)quotacheck –cf /home 4)eduquota –u username
LVM Reduce or Extended	1)resize2fs /dev/vg1/data 12M 2)lvreduce –L 12M /dev/vg1/data
LVM Create	1)pvcreate /dev/had6 /dev/hda7 /dev/hda8 2)vgcreate /dev/vg0 /dev/hda6 /dev/hda7 /dev/hda8 3)lvcreat –L 20M –n /dev/vg1/data
ACL	1)setface –m u:username:permission file
Samba	1)install samba* 2)add samba user 3)change ownership 4)create the samba password 4)/etc/samba/smb.conf,path,writable,read only

Rsync	-e,-a.-z,-v,-=r
TCP	Connection,3 way handshake,acknologment,low speed
UDP	Connectionless protocol, no 3 way handshake ,no acknologment ,high speed DNS is Normally use UDP DNS,DHCP,TFTP
Iptables	Iptables –A Input –s 0/0 –d 12.12.0.5 –p TCP –j ACCEPT
Awk	ls –l \| awk ‘{ print $3 }’
Df	Partition
Du	Folder size
Network Monitor Analysis	Monitor network traffic- capture Network Traffic
Network	/etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-IP Address
Mysql

Request Time Out	Turn off firewall
Destination Host unreachable	Maintain the Same IP

Unix Important Run Level | Difference between Linux and Unix Run level

2010-11-22T14:26:00.000-08:00

Unix Operating System It has Six Run Level
0 System is running under PROM Monitor
s or S – Single user mode with critical file system mounted and accessible
1- Single User Administrative State with access available file system.
2- Multi user mode without networking
3- Multi user mode with networking
4 –Not used
5 –Shut Down & power off
6- Reboot to the Default Run Level

Difference between Unix & Linux Run Level | comparison Between Unix and Linux run level
Same Run Level Linux and Unix System
1,2,3,4,6 these Rune level are same
Different run level

Linux	Unix
0- single user mode	0 system running under PROM
5 Graphical user mode	5 shut down
S,s Not available	S,s single user mode with critical file system

Solaris Administration Package Information Patches Information

2010-11-22T14:23:00.001-08:00

Pkgtrans-Translate package from one format to another
Pkgadd- install package
Pkgrm – Remove the Package
Pkginfo-Display the package information
Pkgchk-check the Package Installation state

/var/sadm/pkg directory maintain the record of al installed package
#pkginfo –l
#pkginfo –l SUNWman Information about specific package

PATCH IN Sun Solaris OE
Patch contains the collection of files and directories.Some patch contain the product enhancement

Maintain The Data Consistencies Using fsck Command

2010-11-22T14:20:00.000-08:00

System maintain the Data consistencies using fsck command.
It is Maintain the Data Consistency in the Following Format
1)Data block consistency, 2)Cylinder Ground
Block Consistency 3)Super Block Consistency,
4)Lost+found Directory 5)inode consistency
Fsck usage in Unix
#fsck /dev/rdsk/c0t0d0s7
#fsck /export/home
#fsck –o f,p /dev/rdsk/c0t0d0s5 – check repair the file system
f- Force
p- Non Interactive - Automatic Repair - without ask yes/no

To use backup super block
#fsck –o b=32 /dev/rdsk/c0t0d0s7
Unix Command quot – Summarize File system Owner ship
In the Linux Operating system while Booting it will check file system,it is metion the /etc/fstab whether it is need to check or not the file system while booting.

Unix Important File System -Unix File System UFS UDFS tmfs swapfs

2010-11-22T14:16:00.000-08:00

UFS- Unix File System- it contain the Disk Label,bootblk,Primary superblock,First cylinder Group,Backup Super block,Cylinder Group Block,Inode Table,Data block, then it contain the same thing in the Secondary Group.
Bootstrap Program -Boot Block-bootblk –- only the root file system has an active boot block.

How To Create New ufs file system.
#newfs /dev/rdsk/c1t0d0s0
udfs – Universal Disk Format File system
tmfs- Temporary File system- tmpfs file system is create and destroyed every time system is rebooted.
Swapfs- Swap file system kernel manage swap space on disk

How To Configure Kick Start In Red hat Linux

2010-11-19T13:15:00.000-08:00

By using Kick start we can do remote installation using NFS,http,FTP,CD-ROM,
if we want to install lot of system with same configuration,
we can create the configuration file (ks.cfg -kick start file) This method is known as Kick start.
#yum install system-config-kickstart >> install the kick start
#system-config-kickstart >> open the kick start GUI Windows
while in these set-up it will ask the basic setting about
Basic configuration,Installation Method,Boot Loader Option,Partition Information,Network configuration,Authentication,Firewall Configuration,Display configuration,Package selection,Pre-installation script,Post-installation script,
Generate ks.cfg file
Add the following line.
@admin-tools
@base
@base-x
@core
@dialup
@editors
@games
@gnome-desktop
@graphical-internet
@graphics
@java
@office
@printing
@sound-and-video
@text-internet
Then save these file as ks.cfg
For NFS through Kicks start installation
#mkdir /rhel5kickstart
#cp ks.cfg /rhel5kickstart
ADD the following line under /etc/exports
/rhel5kickstart *(rw)
#service nfs restart
If we use the http web server copy the ks.cfg file into /var/ww/html web server Document Root Directory.
In the client System
#Boot:linux ks >> if it NFS
#boot:linux ks=http://192.168.0.1/ks.cfg >> we need to configure web server | kickstart file ks.cfg

How To Install FTP in Redhat Linux vsftpd-very secure ftp daemon

2010-11-19T13:05:00.000-08:00

1)Install the vsftp package
#yum install vsftp*
2)switch on the vsftp
#chkconfig vsftpd on
Then check whether vsftpd is installed and working perfeclty or not
We can also verify whether vsftpd function is running or not
#netstat -a | grep ftp
#netstat -tulpn | grep :21
-l list the listening server socket
-p display PID/program name for socket
-n numeric
How To Connect The FTP
#ftp IPADDRESS
Enter the User Name And Password or anonumous
After connect we can get the information regarding send and receive file using help command
Important ftp Configuration file
/etc/vsftpd/ftpusers >> list of user allowed or denied Permanently(userlist_enable , userli
/etc/vsftpd/user_list >> list of user allowed or denied
/etc/vsftpd/vsftpd.conf >> configuration file
if userlist_deny=NO, only allow users in this file
else if userlist_deny=YES (default), never allow users in this file
FTP Port Number
ftp 20 data
ftp 21 control

How To Create Primary Extended Logical Linux windows File System

2010-11-19T04:00:00.000-08:00

Whenever we create the file system. it will create the Primary Partition,Extended Partition,Logical Partition, it is applicable for all Linux and Windows Operation System,
Primary Paritition>> Operating System will be install. We will create the four primary partition.
Then Extended Partition will be created. under these extended partition Logical partition will be create.
For Example If we create the extended partition up to 4GB.Under the 4GB we can create the Logical Partition.Like
LogVol00 / ext3
LogVol01 swap
/dev/sda1 /boot

If we create the custom Layout it will create the partition like following
/dev/sda1 / ext3
/dev/sda2 /usr ext3
/dev/sda3 swap
/dev/sda4 Extended
/dev/sda5 /disk3 ext3
/dev/sda6 /disk2 ext3
Here /dev/sda4 is Extended under these Extended we /dev/sda5,6 these two logical partition will be create.

Write C-Program To Create Message Queue Print Message queue id | Remove The Message Queue.

2010-11-18T15:20:00.000-08:00

Create Print Message queue id | Remove The Message Queue.
#include&alt;sys/types.h>
#include&alt;sys/ipc.h>
#include&alt;sys/msg.h>
main()
{
key_t key = 100;
int i,msqid;
msqid = msgget(key,IPC_CREAT | 0666);
if (msqid &alt; 0)
perror ("faild to creat message q");
else
perror("creat message q");
}
Create Message Queue

Print message queue id.
#include &alt;sys/types.h>
#include &alt;sys/ipc.h>
#include &alt;sys/msg.h>
#define KEY ((key_t) 98765L)
#define PERMS 0666
main()
{
int i, msqid;
for(i = 0; i &alt; 10; i++)
{
if ( (msqid = msgget(KEY, PERMS | IPC_CREAT)) &alt; 0)
perror("cant creat message q");
printf("msqid = %d\n", msqid);
if (msgctl(msqid, IPC_RMID, (struct msqid_ds *) 0) &alt; 0 )
perror("cant remove message q");
}
}
print message queue id.

Remove the message queue.
#include&alt;sys/ipc.h>
#include&alt;stdio.h>
#include&alt;sys/msg.h>
#include&alt;errno.h>
main()
{
key_t key = 100;
int i,msqid;
if(msgctl(msqid,IPC_RMID,0)&alt;0)
{
perror("msgctl fail ");
}
} Remove the message queue.

Write a c-program to create a semaphore.

2010-11-18T15:16:00.000-08:00

c-program to create a semaphore.
#include&alt;stdio.h>
#include&alt;sys/types.h>
#include&alt;sys/ipc.h>
#include&alt;sys/sem.h>
main()
{
int semid, key,nsems;
key = (key_t)0x20;
nsems = 1;
semid = semget(key,nsems,IPC_CREAT | 0666);
printf("created semaphore id %d\n,semid");
}
c-program to create a semaphore.

Write a c-program to create a shared memory.

2010-11-18T15:15:00.001-08:00

c-program to create a shared memory.#include<stdio.h&alt;
#include<sys/types.h&alt;
#include<sys/ipc.h&alt;
#include<sys/shm.h&alt;
main()
{
int shmid;
shmid = shmget((key_t)0x1000, 10, IPC_CREAT | 0666);
if(shmid < 0)
{
printf("creation of shared memory segment failed");
}
printf("successfully created with shmid %d \n",shmid);
}c-program to create a shared memory.

Write A C-Program To Demonstrate Socket For Stream Server.

2010-11-18T15:14:00.001-08:00

Demonstrate Socket For Stream Server.
include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<errno.h>
#include<netinet/in.h>
main(int argc,char *argv[])
{
int sockfd,newfd,child,nbytes,nbyte;
struct sockaddr_in myaddr;
char buff[512];
if(argc!=2)
{
printf("usage: server port\n");
}
if((sockfd=socket(AF_INET,SOCK_STREAM,0))<0)
{
perror("socket failed");
}
myaddr.sin_family=AF_INET;
myaddr.sin_port=htons(atoi(argv[1]));
myaddr.sin_addr.s_addr=htonl(0);
if(bind(sockfd,(struct sockaddr *) &myaddr,sizeof(myaddr))<0)
{
perror("bind failed");
}
if(listen(sockfd,5)<0)
{
perror("listen failed");
}
for( ; ; )
{
if((newfd=accept(sockfd,0,0))<0)
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{
perror("accept failed");
}
if((child=fork())<0)
{
perror("fork failed");
}
if(child==0)
{
close(sockfd);
while((nbytes=read(newfd,buff,512))!=0)
{
if(nbytes<0)
{
perror("read eroor");
}
nbyte=sizeof(buff);
if(write(newfd,buff,nbytes)!=nbytes)
{
perror(" write failed:server");
}
}
}
}
}
Demonstrate Socket For Stream Server.

Write A C-Program To Demonstrate Socket For Stream Client.

2010-11-18T15:12:00.000-08:00

Demonstrate Socket For Stream Client.
#include<stdio.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<arpa/inet.h>
#include<errno.h>
#include<netinet/in.h>
#define SERV_HOST_ADDR "192.168.1.42"
main(int argc,char *argv[])
{
int sockfd,nbytes,nbyte,newfd;
char buff[512];
struct sockaddr_in seraddr;
if(argc!=3)
{
printf("usage port: client serverport,servaddr\n");
}
if((sockfd=socket(AF_INET,SOCK_STREAM,0))<0)
{
perror("socket failed");
}
seraddr.sin_family=AF_INET;
seraddr.sin_port=htons(3490);
seraddr.sin_addr.s_addr=inet_addr(SERV_HOST_ADDR);
if(connect(sockfd,(struct sockaddr *) &seraddr,sizeof(seraddr))<0)
{
perror("connection failed");
}
while((nbytes=read(0,buff,512))!=0)
{
if(nbytes<0)
{
perror("read fail");
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}
if(write(sockfd,buff,nbytes)!=nbytes)
{
perror("write failed");
}
}
if((nbyte=read(sockfd,buff,512))!=nbytes)
{
perror("read failed");
}
if(write(newfd,buff,nbytes)!= nbytes)
{
perror("write failed");
}
}Write a c-program to demonstrate socket for stream client.

Demonstrate Socket For Datagram Client Unix C Program

2010-11-10T13:00:00.000-08:00

Important Funciton and Keyword For socket Data gram For client
Initialize the variable
int sockfd,nbytes,addrlen;
Check Using If function, struct sockaddr_in *, &myaddr,sizeof(myaddr is Greater Than zero
if(bind(sockfd,(struct sockaddr_in *) &myaddr,sizeof(myaddr))<0)
struct sockaddr_in myaddr,servaddr;

Source Code Programming For Socket Data gram Client

#include<stdio.h>
#include<errno.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
main(int argc,char * argv[])
{
int sockfd,nbytes,addrlen;
char buff[512];
struct sockaddr_in myaddr,servaddr;
if(argc!=2)
{
printf("usage port: client");
}
if((sockfd=socket(AF_INET,SOCK_DGRAM,0))<0)
{
perror("socket failed: client");
}
myaddr.sin_family=AF_INET;
myaddr.sin_port=htons(INADDR_ANY);
myaddr.sin_addr.s_addr=htonl(0l);
if(bind(sockfd,(struct sockaddr_in *) &myaddr,sizeof(myaddr))<0)
{
perror("bind failed: client");
}
if((nbytes=read(0,buff,512))<0)
{
perror("read failed: client");
}
servaddr.sin_family=AF_INET;
servaddr.sin_port=htons(atoi(argv[1]));
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servaddr.sin_addr.s_addr=htonl(0l);
if(sendto(sockfd,buff,nbytes,0,(struct sockaddr *)
&servaddr,sizeof(servaddr))!=nbytes)
{
perror("send failed: client");
}
if(write(1,buff,nbytes)!=nbytes)
{
perror("write failed: client");
}
}socket for datagram client Unix C Program

Demonstrate Socket For Server Linux Unix C programming

2010-11-10T12:56:00.000-08:00

cpp-program to demonstrate socket for server.
Important Function And keyword.
Initialize the socket
int sockfd=socket(AF_INET,SOCK_STREAM,0);
Get the Hostname
gethostname(hostname,48);
Assign the PortNumber
cout<<", port: "<<<"\n\n";
Source Code Programming For Server Socket
#include<
sys/socket.h>
#include<arpa/inet.h>
#include<iostream.h>
#include<sys/types.h>
#include<string.h> i
nt makelistener() { int sockfd=socket(AF_INET,SOCK_STREAM,0); if(sockfd<0)
{
cerr<<"could not create socket\n";
return -1;
}
struct sockaddr_in s1;
bzero((char *) &s1,sizeof(s1));
s1.sin_family=AF_INET;
s1.sin_addr.s_addr=INADDR_ANY;
s1.sin_port=0;
if(bind(sockfd,(sockaddr *) &s1,sizeof(s1))<0)
{
cerr<<"could n't bind address to socket\n";
return -1;
}
char hostname[48];
gethostname(hostname,48);
size_t length;
length=sizeof(s1);
getsockname(sockfd,(sockaddr *) &s1,&length);
cout<<"\nlistening on host: "<<hostname;
cout<<", port: "<<ntohs(s1.sin_port)<<"\n\n";
if(listen(sockfd,1)<0)
{
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cerr<<"couldn't listen().\n";
return -1;
}
cout<<"ready for incoming connections\n";
return sockfd;
}
int main()
{
int sockfd=makelistener();
if(sockfd<0)
return -1;
for( ; ;)
{
cout<<"server waiting for connections\n";
struct sockaddr_in s2;
size_t length=sizeof(s2);
int conn=accept(sockfd,(sockaddr *) &s2,&length);
cout<<"server accepted connection\t: "<<conn<<"\n";
char data[128];
char message1[128];
int ack1;
int msglen=read(conn,data,128);
cout<<"server got "<<msglen<<" byte message: "<<data<<"\n";
write(conn,&msglen,sizeof(msglen));
cout<<"enter message for client\n";
cin.getline(message1,128);
write(conn,message1,strlen(message1));
read(conn,&ack1,sizeof(ack1));
cout<<"the client got "<<ack1<<" bytes\n";
close(conn);
return 0;
}
return demonstrate socket for server

cpp-program To Demonstrate Socket For Client.

2010-11-10T12:49:00.000-08:00

C Program To Demonstrate Socket For Client. Her I mention the Important Function to perform the socket.
cin.getline(server_host,80);
struct hostent *hostptr=gethostbyname(server_host);
bcopy(hostptr->h_addr, (char *) &dest.sin_addr, hostptr->h_length);#include<iostream.h>

Source Coding For socket Client

#include<sys/types.h>
#include<netdb.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<stdio.h>
#include<string.h>
int serverconnect()
{
char server_host[80];
u_short server_port;
cout<<"enter the hostname the server is running on\n";
cin.getline(server_host,80);
cout<<"enter the port number the server is listening on\n";
cin>>server_port;
cin.ignore(1,'\n');
int sock;
sock=socket(AF_INET,SOCK_STREAM,0);
struct sockaddr_in dest;
bzero((char *) &dest,sizeof(dest));
struct hostent *hostptr=gethostbyname(server_host);
if(NULL==hostptr)
{
cerr<<"error looking up host "<<server_host<<"\n";
return -1;
}
dest.sin_family=AF_INET;
bcopy(hostptr->h_addr, (char *) &dest.sin_addr, hostptr->h_length);
dest.sin_port=htons(server_port);
cout<<"trying to connect\n";
if(connect(sock, (sockaddr *) &dest, sizeof(dest)))
{
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cout<<"couldn't connect\n";
return -1;
}
cout<<"connection established\n";
return sock;
}
int main()
{
int conn=serverconnect();
if(conn<0)
return -1;
char data[128];
char message[128];
int ack;
cout<<"enter message for server: \n";
cin.getline(message,128);
write(conn,message,strlen(message));
read(conn,&ack,sizeof(ack));
cout<<"the server got "<<ack<<" bytes\n";
int msglen=read(conn,data,128);
cout<<"client got "<<msglen<<" bytes message: "<<data<<" \n ";
write(conn,&msglen,sizeof(msglen));
close(conn);
return 0;
}
demonstrate socket for client.

Unix Basic Shell SCript Programming- Check Case Sensitive- Find Numer of Links

2010-11-09T13:49:00.000-08:00

Write a shell program to know whether the given character is a number or
small case letters or capital letters by using ‘case’.
clear
echo "enter a character"
read c
case $c in
[0-9]) echo "these r numbers";;
[a-z]) echo "these r small";;
[A-Z]) echo "these r caps";;
*)
echo "invalid argument";;
esac
check number or small case letters or capital letters by using ‘case’.
Write a shell program to perform add, sub, mul, div by choice.
clear
echo "1.add"
echo "2.sub"
echo "3.mul"
echo "4.div"
echo "enter a,b values"
read a
read b
read ch
case $ch in
1)c=` expr $a + $b `
echo $c;;
2)c=` expr $a - $b `
echo $c;;
3)c=` expr $a \* $b `
echo $c;;
4)c=` expr $a / $b `
echo $c;;
*)echo "invalid
Write a shell program to know the number of links of a file.
clear
echo "enter a file"
read fn
ls -l $fn | awk '{print $2}'
shell program to know the number of links of a file.