Gathering System Information; System Processes - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

Chapter 38.

Gathering System Information

Before you learn how to configure your system, you should learn how to gather essential system
information. For example, you should know how to find the amount of free memory, the amount of
available hard drive space, how your hard drive is partitioned, and what processes are running. This
chapter discusses how to retrieve this type of information from your Red Hat Enterprise Linux system
using simple commands and a few simple programs.

38.1. System Processes

The ps ax command displays a list of current system processes, including processes owned by other
users. To display the owner alongside each process, use the ps aux command. This list is a static
list; in other words, it is a snapshot of what was running when you invoked the command. If you want a
constantly updated list of running processes, use top as described below.
The ps output can be long. To prevent it from scrolling off the screen, you can pipe it through less:
ps aux | less
You can use the ps command in combination with the grep command to see if a process is running.
For example, to determine if Emacs is running, use the following command:
ps ax | grep emacs
The top command displays currently running processes and important information about them
including their memory and CPU usage. The list is both real-time and interactive. An example of output
from the top command is provided as follows:
top - 15:02:46 up 35 min,
Tasks: 110 total, 1 running, 107 sleeping,
Cpu(s): 41.1% us, 2.0% sy,
Mem: 775024k total,
Swap: 1048568k total,
PID USER PR NI
4624 root 15
4926 mhideo 15
6475 mhideo 16
4920 mhideo 15
1 root 16
2 root 34 19
3 root 5 -10
4 root 6 -10
5 root 5 -10
29 root 5 -10
47 root 16
50 root 11 -10
30 root 15
49 root 16
To exit top, press the q key.
4 users, load average: 0.17, 0.65, 1.00
0.0% ni, 56.6% id,
772028k used,
176k used, 1048392k free,
VIRT RES SHR S %CPU %MEM
0 40192 18m 7228 S 28.4
0 55564 33m 9784 S 13.5
0 3612 968 760 R
0 20872 10m 7808 S
0 1732 548 472 S
0 0 0 S
0 0 0 S
0 0 0 S
0 0 0 S
0 0 0 S
0 0 0 0 S
0 0 0 S
0 0 0 0 S
0 0 0 0 S
0 stopped, 2 zombie
0.0% wa, 0.3% hi,
2996k free, 68468k buffers
441172k cached
TIME+ COMMAND
2.4 1:23.21 X
4.4 0:25.96 gnome-terminal
0.7 0.1 0:00.11 top
0.3 1.4 0:01.61 wnck-applet
0.0 0.1 0:00.23 init
0.0 0.0 0:00.00 ksoftirqd/0
0.0 0.0 0:00.03 events/0
0.0 0.0 0:00.02 khelper
0.0 0.0 0:00.00 kacpid
0.0 0.0 0:00.00 kblockd/0
0.0 0.0 0:01.74 pdflush
0.0 0.0 0:00.00 aio/0
0.0 0.0 0:00.05 khubd
0.0 0.0 0:01.44 kswapd0
0.0% si
525