
1. Using ps aux,you can obtain a useful overview of all the processes running on the Red Hat. The a option means to show all processes, x means to show even processes that don’t have a control terminal, and u selects the “user oriented” output format. Here’s an example of ps aux output:
# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT TIME COMMAND
root 1111 0 0 0 0 ? SN 0:00 /usr/sbin/sshd
root 1134 0 0 0 0 ? Ss 0:00 rpc.statd
root 1235 0 0 0 0 ? S 0:00 rpc.idmapd
root 1445 0 0 0 0 ? Sroot 1556 0 0 0 0 ? Ss 0:00 udevd
root 2134 0 0 0 0 ? Sroot 2275 0 0 0 0 ? SN 0:00 sendmail: accept
root 2545 0 0 0 0 ? Sroot 2956 0 0 0 0 ? SN 0:00 [ksoftirqd/0]
Additional note:
• USER – Username of the process’s owner
• PID – Process ID
• %CPU – Percentage of the CPU this process is using
• %MEM – Percentage of real memory this process is using
• VSZ – Virtual size of the process
• RSS – Resident set size (number of pages in memory)
• TTY – Control terminal ID
• STAT – Current process status:
– R = Runnable D= In uninterruptible sleep
– S = Sleeping (< 20 sec) T = Traced or stopped
– Z = Zombie
Additional flags:
– W = Process is swapped out
– < = Process has higher than normal priority
– N = Process has lower than normal priority
– L = Some pages are locked in core
– s = Process is a session leader
• TIME CPU – time the process has consumed
• COMMAND – Command name and arguments
2. Another useful set of arguments for Red Hat is lax, which provides more technical information. The a and x options are as above (show every process), and l selects the “long” output format. ps lax is also slightly faster to run than ps aux because it doesn’t have to translate every UID to a username. Below are ps lax example, includes fields such as the parent process ID (PPID), nice value (NI), and the type of resource on which the process is waiting (WCHAN).
# ps lax
F UID PID PPID PRI NI VSZ RSS WCHAN STAT TIME COMMAND
1 0 1146 1 16 0 1221 482 syslog Ss 0:00 init [5]
1 0 1884 1 34 0 0 444 worker S 0:00 rpc.statd
5 32 1996 1 21 0 0 255 - S 0:00 xinetd -sta
5 0 2186 1 17 0 2252 111 - S1 26 2221 1 11 0 3345 764 syslog Ss 0:00 [events/0]
1 0 2377 1 16 0 5143 897 worker SN 0:00 klogd -x
5 33 2435 1 16 0 8895 210 syslog SN 0:00 sshd