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In this video we'll talk about the
way how you can manage processes with Kill.

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So how does that work? Well, Kill is used
to send signals to a process based on the pid.

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Kill all is a convenient command line utility that
can do the same, but it's based on process name.

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You have already seen me using
killall DD a couple of times.

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Common signals are signal 15, which is sick
term, and that instructs the process to stop.

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This is a nice signal because the
process will have time to finish its work.

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Signal 9 is not so nice because that will
force the process off and nothing will be stopped.

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Other signals are specific to the commands that you are
running. You won't run them very much. You know what

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I want to do? I want to show you
the difference between signal 9 and signal 15 from top.

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So here I'm going to start top again and I'm pressing K. Now
the process that I want to kill is process 7148. That is top itself.

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And next it's asking for a signal. And the
default signal that it wants to send is signal 15,

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which is Sigterm. And sigterm is just fine with
me. So I'm pressing enter and now it's gone.

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Now what is the point that I want to
make? Well, the point that I want to make

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is that if we do it again, this time
7211, which is stop again and I'm going to

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send it signal nine, then this is what
is happening. You see what's happening? Nothing is cleaned.

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Now this is a very clear demo that signal 9
doesn't allow the process to clean up anything at all.

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The result is that if you use Signal
9 on important applications, you might cause some

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damage here. So don't use signal 9, at
least not before you have used signal 15.

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If you do a signal 15, you wait a couple of minutes and the
process is still there, then it might be okay to do a signal 9.

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But normally you should
try to avoid signal 9.

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In case you wonder how can we clean up the
screen. Well, just use clear. Clear is the magical command

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that will always work and it will clear your
screen. And as you can see, little bit stronger reset.

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If the screen output is really a mess,
then you use reset to regenerate new prompt.