Slackware Linux Essentials
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11.4 `kill`

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On occasion, programs misbehave and you'll need to put them back in line. The program -for this kind of administration is called kill(1), and it can be -used for manipulating processes in several ways. The most obvious use of kill is to kill off a process. You'll need to do this if a program -has run away and is using up lots of system resources, or if you're just sick of it -running.

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In order to kill off a process, you'll need to know its PID or its name. To get the -PID, use the ps command as was discussed in the last section. -For example, to kill off process 4747, you'd issue the following:

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-% kill 4747
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Note that you'll have to be the owner of the process in order to kill it. This is a -security feature. If you were allowed to kill off processes started by other users, it -would be possible to do all sorts of malicious things. Of course, root can kill off any process on the system.

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There's another variety of the kill command called killall(1). This program does exactly what it says: it kills all the -running processes that have a certain name. If you wanted to kill off all the running vim processes, you could type the following command:

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-% killall vim
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Any and all vim processes you have running will die off. -Doing this as root would kill off all the vim processes running for all users. This brings up an interesting -way to kick everyone (including yourself) off the system:

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-# killall bash
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Sometimes a regular kill doesn't get the job done. Certain processes will not die with -a kill. You'll need to use a more potent form. If that pesky PID 4747 wasn't responding -to your kill request, you could do the following:

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-% kill -9 4747
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That will almost certainly cause process 4747 to die. You can do the same thing with -killall. What this is doing is sending a different signal to the -process. A regular kill sends a SIGTERM (terminate) signal to the process, which tells it to finish -what it's doing, clean up, and exit. kill -9 sends a SIGKILL (kill) signal to the process, which essentially drops it. -The process is not allowed to clean-up, and sometimes bad things like data corruption -could occur by killing something with a SIGKILL. There's a -whole list of signals at your disposal. You can get a listing of signals by typing the -following:

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-% 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  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
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The number must be used for kill, while the name minus the -leading “SIG” can be used with killall. Here's -another example:

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-% killall -KILL vim
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A final use of kill is to restart a process. Sending a SIGHUP will cause most processes to re-read their configuration -files. This is especially helpful for telling system processes to re-read their config -files after editing.

11.4 kill

11.4 `kill`