To kill a process we use kill command, kill command sends a signal to process. To kill a process you must know process name or process ID. There two command which can be used to kill a program – kill and killall.
Syntax
kill signal PID
Example
kill -9 3726 kill SIGTERM 3726
It should be noted that all user cannot kill all processes. A user can kill only process process belonging to himself. But a user cannot kill processes belonging to other user or system level processes. A root user can kill processes belonging to other user or system level processes.
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Below table has details about signal and their effect.
| SIgnal Name | Signal Value | Signal effect |
| SIGNUP | 1 | Hangup |
| SIGKILL | 9 | Kill Signal |
| SIGTERM | 15 | Terminate |
SIGHUP is safest way to kill an application , after closing an process it reloads it along with configuration file and open and closes log file. SIGKILL closes process without saving anything and most unsafe of three. SIGNTERM may kill application immediately some applications may stop and some may not.
Kill multiple process
You can use kill command to kill multiple process in one go.
Syntax
kill signal PID1 PID2 PID3
Example
kill -9 3726 3789 4082 kill SIGTERM 3726 3789 4082
Kill multiple instance of process
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Several command like chrome may have multiple instances running in system. To kill all instance of a process use command killall
Syntax
killall signal process_name
Example
killall -9 chrome kill SIGTERM chrome
This will kill all running instance of chrome process.
