Job Control#
Commands#
Niceness and Priority#
40 niceness values. -20 is highest and 19 is lowest. Default is 0. Child processes inherit niceness of parent. Users can renice processes they own. root can renice any process.
- nice (1) - run a program with modified scheduling priority
- renice (1) - alter priority of running processes
Print process list with priority and niceness columns:
ps -efl
[root@server1 ~]# ps -efl | head
F S UID PID PPID C PRI NI ADDR SZ WCHAN STIME TTY TIME CMD
4 S root 1 0 0 80 0 - 43106 ep_pol Mar02 ? 00:00:01 /usr/lib/systemd/systemd rhgb --switched-root --system --deserialize 31
1 S root 2 0 0 80 0 - 0 kthrea Mar02 ? 00:00:00 [kthreadd]
1 I root 3 2 0 60 -20 - 0 rescue Mar02 ? 00:00:00 [rcu_gp]
1 I root 4 2 0 60 -20 - 0 rescue Mar02 ? 00:00:00 [rcu_par_gp]
1 I root 5 2 0 60 -20 - 0 rescue Mar02 ? 00:00:00 [slub_flushwq]
1 I root 6 2 0 60 -20 - 0 rescue Mar02 ? 00:00:00 [netns]
1 I root 8 2 0 60 -20 - 0 worker Mar02 ? 00:00:00 [kworker/0:0H-events_highpri]
1 I root 10 2 0 60 -20 - 0 rescue Mar02 ? 00:00:00 [mm_percpu_wq]
1 I root 12 2 0 80 0 - 0 rcu_ta Mar02 ? 00:00:00 [rcu_tasks_kthre]
View default niceness with nice command:
[root@server1 ~]# nice
0
Process Signals#
List available signals with kill -l:
[root@server1 ~]# kill -l
1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP
6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1
11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM
16) SIGSTKFLT 17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ
26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO 30) SIGPWR
31) SIGSYS 34) SIGRTMIN 35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3
38) SIGRTMIN+4 39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8
43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13
48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12
53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7
58) SIGRTMAX-6 59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2
63) SIGRTMAX-1 64) SIGRTMAX
Most common process signals:
| Signal Number | Signal Name | Action |
|---|---|---|
| 1 | SIGHUP | Hang up signal causes a process to disconnect itself from a closed terminal that it was tied to. Also used to instruct a running daemon to re-read its configuration without a restart |
| 2 | SIGINT | The ^c (Ctrl+c) signal issued on the controlling terminal to interrupt the execution of a process. |
| 9 | SIGKILL | Terminates a process abruptly. |
| 15 | SIGTERM | Sends a soft termination signal to stop a process in an orderly fashion. This is the default signal if none is specified with the command. |
| 18 | SIGCONT | Same as using the bg command to resume. |
| 19 | SIGSTOP | Same as using the Ctrl+z to suspend a job. |
| 20 | SIGTSTP | Same as using the fg command. |
Commands#
- kill (1) - terminate a process
- pkill (1) - look up, signal, or wait for processes based on name and other attributes