25 Linux Important Points Tricks Tips

1)Don't give full permission to /var/ directory
REASON: it contain important process(PID) related file and it'll affect the ssh connectivity & OS.
2)Don't Give full permission to /tmp directory.
REASON:it will affected gnome related files & You won't get the proper graphical display.
Error Message:
Failed to contact configuration server; some possible causes are that you need to enable TCP/IP networking for ORBit, or you have stale NFS locks due to a system crash. See http://www.gnome.org/projects/gconf/ for information. (Details - 1: IOR file '/tmp/gconfd-oracle/lock/ior' not opened successfully, no gconfd located: No such file or directory 2: IOR file '/tmp/gconfd-oracle/lock/ior' not opened successfully, no gconfd located: No such file or directory)
3)After installed & configure production server take the backup of fstab file it is very very Important.
4)Id "x" respawning too fast: disabled for 5 minutes
These issue we will face in the client node,
Reason: If NFS is not mounting Properly to the client node from the master node, then we will face these problem.
5)cat /proc/cpuinfo | grep sibling - Get the no of core available on physical cpu(or)socket.
6)Difference Between /dev/random & /dev/unrandom
/dev/random
1)it has major device number 1 & Minor number device is 8
2)it is slow key generation compare to /dev/unrandom
3)used for Security of cryptography for application-one time pads
- key generation
#dd if=/dev/random bs=1 count=1024 > random.key
1024+0 records in
1024+0 records out
1024 bytes (1.0 kB) copied, 52.2677 seconds, 0.0 kB/s
It is used to Generate the random key.
7)Sas Vs Sata Hard disk
SAS - Serial Attached SCSI
1)Sata Transfer Rate is 6GB/s
SATA - Serial ATA
1)Sata Transfer Rate is 3 GB/s
/dev/unrandom
1)it has major device number is 1 and Minor number device is 9
2)To generate the large file used for some kind of testing.
8)BIOS Setup Features
Turbo Boost Technology – Maximize potential Frequency when it is required
CPU Cache - Enable Faster to Local Memory Reduce the inter Process Communication Traffic - Improve CPU utilization- Performance - Helping Process remain focus on task with less interruption.
Thermal Technology - used to maintain the minimal Power consumption using sensor.
9)HP ProLiant servers Intergrate Light Out Advantage
1)Remote Power Capabilities
2)Graphical Remote Console 8X fasterwith ILo3.
3)Team collaboration up to 6 users.
4)Total Control 

ILO Accesss - Particular system console.
Onboard Administrator - The the console for the complete BLADE System. 10)Serial and Parallel Job(Distributed Computing)
1)A problem broken into discrete series of instruction,
Instructions are executed one after and another.
One Instruction may execute at moment at time.

2)Distributed Computer - A problem is divided into multiple task and solved concurrently
Multiple instruction it execute at moment at time,
11)How to configure outlook express or Mozilla thunder bird.
To configure Mail Box Requirement
1)Login Username/Password
2)Incoming/Outgoing Mailserver Pop3 IP and Pop3 IP should ping from that Local IP.
Configuration
1)POP3 Mail Sever -Incoming(Getting mail) server settings(IP/USERNAME- POP3 protocol-110)
2)SMTP Mail Server -Outgoing(Sending mail) server SMTP(IP/User name-SMTP Protocol-25)
12)Get Log file for Particular Processor or service
a)get the process id for that process or service for example if process id is 3067
b)ls -l /proc/3067/fd [list the process file descriptor ]
c)From these output we can find out.
13) a)Even though file has the full permission. we can't remove, create soft link or move the file.
In these case we have to check the attributes using lsattr change attribute chattr.
# lsattr /usr/bin/ssh
s----a------- /usr/bin/ssh
b)lsattr and chattr - `e’ attribute indicates that the file is using extents for mapping the blocks on disk.It may not be removed or changed using chattr

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