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If the parent process never attempts to do so, they will remain on the process 
list. This in and of itself may not really be a big issue, since these processes aren't 
technically doing anything. But if their presence is causing problems and you can't 
kill them, you could try to send 
SIGKILL
 to the process. There should be no harm in 
killing a zombie process, but you would want to give them time to be reaped first.
To send signal 
9
 to a process, you would use the 
-9
 option of the 
kill
 command. 
It should go without saying, though, to make sure you're executing it against the 
proper process ID:
sudo kill -9 31258 
Just like that, the process with a PID of 
31258
 will vanish without a trace. Anything 
it was writing to will be in limbo, and it will be removed from memory instantly. If, 
for some reason, the process still manages to stay running (which is extremely rare), 
you probably would need to reboot the server to get rid of it, which is something I've 
only seen in a few, very rare cases. An example of this is a zombie process, which is a 
process that runs but isn't impacted by having signals sent to it, since such a process 
won't be scheduled for CPU time anyway. When it all comes down to it, if 
kill -9
 
doesn't get rid of the process, nothing will.
Another method of killing a process is with the 
killall
 command, which is probably 
safer than the 
kill
 command (if for no other reason than there's a smaller chance 
you'll accidentally kill the wrong process). Like 
kill
, 
killall
 allows you to send 
SIGTERM
 to a process, but unlike 
kill
, you can do so by name. In addition, 
killall
 
doesn't just kill one process, it kills any process it finds with the name you've given 
it as an option. To use 
killall
, you would simply execute 
killall
 along with the 
name of a process:
sudo killall myprocess 
Just like the 
kill
 command, you can also send signal 
9
 to the process as well:
sudo killall -9 myprocess 
Again, use that only when necessary. In practice, though, you probably won't use 
killall -9
 very often (if ever), because it's rare for multiple processes under the 
same process name to become locked. If you need to send signal 
9
, stick to the 
kill
 
command if you can.

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Chapter 7