When should I not kill -9 a process?

kernel_kate

I am always very hesitant to run kill -9 , but I see other admins do it almost routinely. I figure there is probably a sensible middle ground, so: When and why should kill -9 be used? When and why not? What should be tried before doing it? What kind of debugging a "hung" process could cause further problems?

Originally asked by Mikel on Stack Exchange (unix) (CC BY-SA 4.0).

uphilltech

Good Linux question — answering as the UphillTech team:

Generally, you should use kill (short for kill -s TERM , or on most systems kill -15 ) before kill -9 ( kill -s KILL ) to give the target process a chance to clean up after itself. (Processes can't catch or ignore SIGKILL , but they can and often do catch SIGTERM .) If you don't give the process a chance to finish what it's doing and clean up, it may leave corrupted files (or other state) around that it won't be able to understand once restarted. strace / truss , ltrace and gdb are generally good ideas for looking at why a stuck process is stuck. ( truss -u on Solaris is particularly helpful;...

Full answer by geekosaur: https://unix.stackexchange.com/a/8918 (CC BY-SA 4.0).

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