Process Management
The ps command enumerates the processes running on your system. The ps command is similar to the Task Manager in Windows OS, in that it lists the running processes (programs).
[root@server ~]# ps PID TTY TIME CMD 2980 pts/1 bash 2997 pts/1 ps[root@server ~]# which ps/bin/psAs per existing standards required binaries are to exist in /bin directory and ps is one such binary.
[root@server ~]# rpm -ql procps-3.2.3-7EL/bin/ps/lib/libproc-3.2.3.so/sbin/sysctl/usr/bin/free/usr/bin/pgrep/usr/bin/pkill/usr/bin/pmap/usr/bin/skill/usr/bin/slabtop/usr/bin/snice/usr/bin/tload/usr/bin/top/usr/bin/uptime/usr/bin/vmstat/usr/bin/w/usr/bin/watch/usr/share/doc/procps-3.2.3(Output filtered)The ps with the –e option will list all the processing running on the system
[root@server ~]# ps -e PID TTY TIME CMD 1 ? init 2 ? ksoftirqd/0 3 ? events/0 4 ? khelper 5 ? kacpid 18 ? kblockd/0 28 ? pdflush 29 ? pdflush 31 ? aio/0 19 ? khubd 30 ? kswapd0 105 ? kseriod 176 ? scsi_eh_0 188 ? kmirrord/0 197 ? kjournald 1042 ? udevdThe command ps –aux or ps aux (BSD Style) will list all process and their ids and will provide detailed information about the processes running on the system.
[root@server ~]# ps -auxWarning: bad syntax, perhaps a bogus '-'? See /usr/share/doc/procps-3.2.3/FAQUSER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMANDroot 1 0.0 0.2 1664 556 ? S 0:00 init [5]root 2 0.0 0.0 0 0 ? SN 0:00 [ksoftirqd/0]root 3 0.0 0.0 0 0 ? S< 07:36 0:00 [events/0]root 4 0.0 0.0 0 0 ? S< 07:36 0:00 [khelper]root 5 0.0 0.0 0 0 ? S< 07:36 0:00 [kacpid]root 18 0.0 0.0 0 0 ? S< 07:36 0:00 [kblockd/0]root 28 0.0 0.0 0 0 ? S 0:00 [pdflush]root 29 0.0 0.0 0 0 ? S 0:00 [pdflush]root 31 0.0 0.0 0 0 ? S< 07:36 0:00 [aio/0]root 19 0.0 0.0 0 0 ? S 0:00 [khubd]root 30 0.0 0.0 0 0 ? S 0:00 [kswapd0]root 105 0.0 0.0 0 0 ? S 0:00 [kseriod]root 176 0.0 0.0 0 0 ? S 0:00 [scsi_eh_0]root 188 0.0 0.0 0 0 ? S< 07:36 0:00 [kmirrord/0]root 197 0.0 0.0 0 0 ? S 0:00 [kjournald]root 1042 0.0 0.1 2452 448 ? S<s 0:00 udevdroot 3022 0.8 1.1 5484 3040 pts/2 S 0:07 /usr/lib/vmware-tools/bin32/vmwareroot 3087 0.0 0.3 2808 772 pts/1 R+ 0:00 ps -aux-a all w/ tty, including other users -t by tty
-u by effective user ID (supports names)
-x processes w/o controlling ttys
PROCESS STATE CODES
Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process.
D Uninterruptible sleep (usually IO)
R Running or runnable (on run queue)
S Interruptible sleep (waiting for an event to complete)
T Stopped, either by a job control signal or because it is being traced.
W paging (not valid since the 2.6.xx kernel)
X dead (should never be seen)
Z Defunct ("zombie") process, terminated but not reaped by its parent.
For BSD formats and when the stat keyword is used, additional characters may be displayed:
< high-priority (not nice to other users)
N low-priority (nice to other users)
L has pages locked into memory (for real-time and custom IO)
s is a session leader
l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+ is in the foreground process group
Note: Use ps –aux | less command to display output one page at a time.
[root@server ~]# ps -aux | grep sshd
Warning: bad syntax, perhaps a bogus '-'? See /usr/share/doc/procps-3.2.3/FAQ
root 2037 0.0 0.6 5892 1652 ? Ss 0:00 /usr/sbin/sshd
root 3152 0.0 0.1 2444 352 pts/1 R+ 0:00 grep sshd
The above command filters the ps –aux and lists only the sshd process.
[root@server ~]# ps -aux | grep tty
Warning: bad syntax, perhaps a bogus '-'? See /usr/share/doc/procps-3.2.3/FAQ
root 2199 0.0 0.1 3112 408 tty1 Ss+ 0:00 /sbin/mingetty tty1
root 2201 0.0 0.1 2972 404 tty2 Ss+ 0:00 /sbin/mingetty tty2
root 2202 0.0 0.1 2192 408 tty3 Ss+ 0:00 /sbin/mingetty tty3
root 2203 0.0 0.1 2476 408 tty4 Ss+ 0:00 /sbin/mingetty tty4
root 2452 0.0 0.1 1476 408 tty5 Ss+ 0:00 /sbin/mingetty tty5
root 2525 0.0 0.1 2464 408 tty6 Ss+ 0:00 /sbin/mingetty tty6
root 3154 0.0 0.2 5028 672 pts/1 S+ 0:00 grep tty
The above command filters all processes and lists only tty (Tele Type Terminals) processes.
[root@server ~]# ps -t tty1
PID TTY TIME CMD
2199 tty1 mingetty
[root@server ~]# ps -t tty2
PID TTY TIME CMD
2201 tty2 mingetty
The above command lists only -tty processes, -t option.
The who command also displays information about tty/pts terminals.
[root@server ~]# who
root :0 Dec 20
root pts/1 Dec 20 (:0.0)
root pts/2 Dec 20 (:0.0)
[root@server ~]# who -a
Dec 20 216 id=si term=0 exit=0
system boot Dec 20
run-level 5 Dec 20 last=S
Dec 20 1497 id=l5 term=0 exit=0
Dec 20 2199 id=1
Dec 20 2201 id=2
LOGIN tty3 Dec 20 2202 id=3
Dec 20 2203 id=4
Dec 20 2452 id=5
Dec 20 2525 id=6
Dec 20 2571 id=x
root ? :0 Dec 20 ? 2829
root + pts/1 Dec 20 . 2978 (:0.0)
root + pts/2 Dec 20 2978 (:0.0)
The pstree utility
[root@server ~]# which pstree
/usr/bin/pstree
[root@server ~]# rpm -qf /usr/bin/pstree
psmisc-21.4-4
[root@server ~]# rpm -ql psmisc-21.4-4
/sbin/fuser
/usr/bin/killall
/usr/bin/pstree
/usr/bin/pstree.x11
/usr/share/locale/de/LC_MESSAGES/psmisc.mo
/usr/share/locale/en/LC_MESSAGES/psmisc.mo
/usr/share/locale/fr/LC_MESSAGES/psmisc.mo
/usr/share/locale/it/LC_MESSAGES/psmisc.mo
/usr/share/locale/pt/LC_MESSAGES/psmisc.mo
/usr/share/locale/sv/LC_MESSAGES/psmisc.mo
/usr/share/man/man1/fuser.1.gz
/usr/share/man/man1/killall.1.gz
/usr/share/man/man1/pstree.1.gz
The pstree command displays the processes in a tree like view.
Process Selections
The free command lists the amount of total memory, used, free, shared, buffers, cached and the swap usage.
[root@server ~]# free
total used free shared buffers cached
Mem: 256044 247204 8840 0 15440 140916
-/+ buffers/cache: 90848 165196
Swap: 524280 0 524280
[root@server ~]#
The free command with the –m option returns the memory and swap in megabytes.
[root@server ~]# free -m
total used free shared buffers cached
Mem: 250 241 8 0 15 137
-/+ buffers/cache: 88 161
Swap: 511 0 511
Use the free command with the –m and –s (seconds) to update the memory usage every 3 seconds.
[root@server ~]# free -m -s 3
total used free shared buffers cached
Mem: 250 241 8 0 15 137
-/+ buffers/cache: 89 160
Swap: 511 0 511
total used free shared buffers cached
Mem: 250 241 8 0 15 137
-/+ buffers/cache: 89 161
Swap: 511 0 511
Use the top command to display information about the processes running on the system. The top command updates the information displayed every 3 seconds.
[root@server ~]# top
top - up , 3 users, load average: 0.05, 0.11, 0.15
Tasks: 76 total, 1 running, 73 sleeping, 2 stopped, 0 zombie
Cpu(s): 6.0% us, 5.6% sy, 0.0% ni, 88.4% id, 0.0% wa, 0.0% hi, 0.0% si
Mem: 256044k total, 247976k used, 8068k free, 15540k buffers
Swap: 524280k total, 0k used, 524280k free, 140992k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2675 root 15 0 38508 15m 5096 S 6.8 6.0 1:09.98 X
2978 root 15 0 38348 14m 8680 S 2.9 5.6 0:17.09 gnome-terminal
24855 root 16 0 2612 940 756 R 0.7 0.4 0:00.12 top
3022 root 15 0 5484 3056 2496 S 0.3 1.2 0:29.69 vmware-toolbox-
1 root 16 0 1664 556 480 S 0.0 0.2 0:00.86 init
2 root 34 19 0 0 0 S 0.0 0.0 0:00.12 ksoftirqd/0
3 root 5 -10 0 0 0 S 0.0 0.0 0:00.22 events/0
4 root 5 -10 0 0 0 S 0.0 0.0 0:00.02 khelper
5 root 15 -10 0 0 0 S 0.0 0.0 0:00.00 kacpid
18 root 5 -10 0 0 0 S 0.0 0.0 0:00.14 kblockd/0
28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pdflush
29 root 15 0 0 0 0 S 0.0 0.0 0:00.44 pdflush
31 root 8 -10 0 0 0 S 0.0 0.0 0:00.00 aio/0
19 root 15 0 0 0 0 S 0.0 0.0 0:00.00 khubd
30 root 15 0 0 0 0 S 0.0 0.0 0:00.12 kswapd0
105 root 25 0 0 0 0 S 0.0 0.0 0:00.00 kseriod
176 root 22 0 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_0
188 root 6 -10 0 0 0 S 0.0 0.0 0:00.00 kmirrord/0
197 root 16 0 0 0 0 S 0.0 0.0 0:00.87 kjournald
Pressing SHIFT+f will bring up a menu to select more options in the top command.
Note: zombie processes tend to be in deep sleep.
[root@server ~]# top --help
top: procps version 3.2.3
usage: top -hv | -bcisS -d delay -n iterations [-u user | -U user] -p pid [,pid ...]
The top command with the –u username option will display usage of a particular user.
[root@server ~]# top -u root
top - up , 3 users, load average: 0.07, 0.05, 0.06
Tasks: 77 total, 1 running, 73 sleeping, 3 stopped, 0 zombie
Cpu(s): 2.8% us, 3.8% sy, 0.0% ni, 93.4% id, 0.0% wa, 0.0% hi, 0.0% si
Mem: 256044k total, 248564k used, 7480k free, 15648k buffers
Swap: 524280k total, 0k used, 524280k free, 141020k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
2675 root 15 0 38508 15m 5112 S 3.3 6.0 1:21.08 X
2978 root 15 0 38216 14m 8680 S 1.6 5.6 0:21.18 gnome-terminal
3022 root 15 0 5484 3056 2496 S 1.0 1.2 0:38.82 vmware-toolbox-
24886 root 17 0 3612 944 760 R 0.7 0.4 0:00.04 top
2189 root 16 0 6524 4004 1612 S 0.3 1.6 0:10.54 hald
2956 root 25 10 32156 18m 10m S 0.3 7.5 0:06.61 rhn-applet-gui
2972 root 15 0 21324 9224 6936 S 0.3 3.6 0:03.83 mixer_applet2
1 root 16 0 1664 556 480 S 0.0 0.2 0:00.93 init
2 root 34 19 0 0 0 S 0.0 0.0 0:00.12 ksoftirqd/0
3 root 5 -10 0 0 0 S 0.0 0.0 0:00.25 events/0
4 root 5 -10 0 0 0 S 0.0 0.0 0:00.02 khelper
5 root 15 -10 0 0 0 S 0.0 0.0 0:00.00 kacpid
18 root 5 -10 0 0 0 S 0.0 0.0 0:00.15 kblockd/0
28 root 20 0 0 0 0 S 0.0 0.0 0:00.00 pdflush
29 root 15 0 0 0 0 S 0.0 0.0 0:00.47 pdflush
31 root 8 -10 0 0 0 S 0.0 0.0 0:00.00 aio/0
19 root 15 0 0 0 0 S 0.0 0.0 0:00.00 khubd
30 root 15 0 0 0 0 S 0.0 0.0 0:00.12 kswapd0
105 root 25 0 0 0 0 S 0.0 0.0 0:00.00 kseriod
176 root 22 0 0 0 0 S 0.0 0.0 0:00.00 scsi_eh_0
188 root 6 -10 0 0 0 S 0.0 0.0 0:00.00 kmirrord/0
197 root 15 0 0 0 0 S 0.0 0.0 0:00.92 kjournald
Changing Priority (renice)
- Open a new terminal and run the top command.
- Open a new terminal and run the sequence command seq 1000000 > seqmilrecord.txt
- Go back to terminal one where you ran top and sort the process in order of high cpu usage.
- Press n to change priority of a process.
- Enter the PID of the process in our case it was seq.
- Enter new renice value to increase or decrease priority of the seq command. Where -19 is the highest value where process gets a highest priority and 20 is the lowest value, meaning the lowest priority.
Killing a Process
Press k in the top menu to kill a process and type in the PID of the process you want to kill (shut).
The kill command.
The kill command is used to kill a process by sending signal to the process using the Process ID(PID).
kill –l
Will list all signals supported by the kill command.
kill processid
Will kill the process whose id was given to kill.
Killall command
The killall command kills all the processes of the given process name.
#killall seq
Will kill all seq processes running in other shells (in background &).
Note: The information listed by ps, top etc is pulled from a filesystem /proc which is mounted in memory. Below is a example of cpuinfo kept in the /proc filesystem.
[root@server ~]# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 3
model name : Intel(R) Pentium(R) 4 CPU 2.40GHz
stepping : 8
cpu MHz : 2389.200
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 5
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss pni ds_cpl
bogomips : 4702.20
The uptime command displays information about the time since the system has been up and running.
[root@server ~]# uptime
up , 3 users, load average: 0.02, 0.08, 0.14
The jobs command is used to display the jobs running in the background. The fg (Foreground) commands is used to display foreground processes running in the shell. Both are inbuilt inside the shell and are not separate binary files.
[root@server ~]#pstree
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