How to kill a process

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 SOLUTION 已验证 - 已更新 2014年四月8日20:06 - 

English 

环境

• Red Hat Enterprise Linux (All Versions)

问题

• How to kill a process ?

决议

Kill command is use to send signal to a process or to kill a process. We typically use kill -SIGNAL

There are other ways to effectively kill a process — killing a process by name, killing a process by specifying part of the name, killing a process by pointing out the process with cursor etc.,

1. Kill Command – Kill the process by specifying its PID

   All the below kill conventions will send the TERM signal to the specified process. For the signals, either the signal name or signal number can be used. You need to lookup the pid for the process and give it as an argument to kill.

   Raw

   $ kill -TERM pid
   
   $ kill -SIGTERM pid
   
   $ kill -15 pid
   

   Example: Kill the firefox process.

   Raw

   $ ps -ef | grep firefox
   1986 ?        Sl     7:22 /usr/lib/firefox-3.5.3/firefox
   
   $ kill -9 1986
   

   Note: It is not a good idea to use kill -9 always, Most programs require some sort of cleanup when it exits. These programs setup a signal handler to perform these cleanup duties as a result of SIGTERM and SIGINT. They would setup a signal handler for SIGKILL if they could, but SIGKILL (kill -9) is untrappable. Using SIGKILL dont give opportunity to cleanup while exiting and dont give opportunity to delete any temporary files, shutdown sockets, remove shared memory segments, close open files, or some other task. This may corrupt database or other important temporary files.

   A process should be sent a SIGTERM signal.

   Raw

   kill 5987
   kill -s TERM 5987
   kill -TERM 5987
   kill -15 5987
   

2. Killall Command – Kill processes by name

   Instead of specifying a process by its PID, you can specify the name of the process. If more than one process runs with that name, all of them will be killed.

   Example: Kill all the firefox processes

   Raw

   $ killall -9 firefox
   

3. Pkill Command – Send signal to the process based on its name

   You can send signal to any process by specifying the full name or partial name. So there is no need for you to find out the PID of the process to send the signal.

   Example: Send SIGTERM to all the process which has sample in its name.

   Raw

   $ pkill sample
   

Pkill Example:

Before sending signal, you can verify which are all the process is matching the criteria using “pgrep -l”, which displays the process ID and process name of the matching processes.

In this example, all the processes are designed to log the signal to signal-log, along with its PID.

Raw

$ pgrep -l sample
12406 sample-server.p
12425 sample-server.p
12430 sample-garbagec

$ pkill -USR1 sample

$ cat signal-log
Name: ./sample-server.pl Pid: 12406 Signal Received: USR1
Name: ./sample-server.pl Pid: 12425 Signal Received: USR1
Name: ./sample-garbagecollector.pl Pid: 12430 Signal Received: USR1

Note: The part of name which you specify should be in the character within the first 15 character of the process name.

诊断步骤

• Check process status. If the process is 'Z' status, you cannot kill it.

Raw

# ps aux|grep -i PROCESS NAME

Raw

To check if signal is block for a specific process run below command

cat /proc/<pid>/status |grep ^Sig
SigQ:   1/62809
SigPnd: 0000000000000000
SigBlk: 0000000056727a01
SigIgn: 0000000000381000
SigCgt: 00000001c98044ff

From above output it is confirmed signals no (1,10,12,13,14,15 etc) are blocked for this process.