The Linux Juggernaut

RAM plays an important role in the performance of a system. So we should monitor this memory usage to troubleshoot system. free is the basic command to get details of RAM and swap usage.

#free

Example :

# free
total used free shared buffers cached
Mem: 3059872 2842016 217856 0 33936 2012684
-/+ buffers/cache: 795396 2264476
Swap: 2000052 67672 1932380

When you see its giving total size, used and free size in bytes. If … Continue Reading

What is a”Core file” ? Ans : A core file is created when a program is crashed/stoped abnormally due to some bug. This will be huge size which contains all the memory info, crash info which is used for programmers to debug the issue and find a solution or patch to that bug.

Why we system administrators are interested in that core files?
Ans : This is because of their size. As we do … Continue Reading

A “defunct” processes is also known as a “zombie” processes. A Zombie process is referred as dead process which is receding on your system thought its completed executing. In one shot we can say its a dead processes. This process will be in your process table and consuming your memory. Having more defunct process will consume your memory which intern slows your system. We have to kill the defunct process in order to free RAM … Continue Reading

Some times its required for us to know what is the RAM used by an application. Suppose in your machine Apache service or Mysql service is consuming up all your RAM. So how to check it? Is there any direct command to do this? The answer to this is no. We have to use two commands to do this. Here is the way to see what is the ram used by a particular Application.… Continue Reading

To see all the process run by a perticular user
#ps -u username u

Example
#ps -u rajesh u

or

To see all the files opened by user
#lsof grep username

Example
#lsof grep rajesh

To see memory used by a perticular user
#ps -u username u awk ‘{print $2}’

Example
ps -u krishna u awk ‘{print $2}’

Now you will get all the PID’s run by user Krishna. So try to get memory usage … Continue Reading

Q. I know the subject is not quite what I want to know, but there is a command to list running processes and I can’t remember what it is? There are many commands to accomplish this. Here is the list.

To see all the process running on a system
#ps -A

Example output :

PID TTY TIME CMD
1 ? 00:00:01 init
2 ? 00:00:00 kthreadd
3 ? 00:00:00 migration/0
4 ? 00:00:00 ksoftirqd/0
5 … Continue Reading