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- In this video, we are
going to explain what you

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can do to manage process priority.

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The thing is that every
user process by default

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is started with the same priority

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And to adjust priorities,
user can use the nice command

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to start processes with
an adjusted priority.

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Non-privileged users
can only run processes

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with a lower priority.

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Privileged users can increase

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and decrease process priority.

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And if you are going to
use the nice command,

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the priority that you
will use reaches from -20,

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which is the highest
priority to positive 19,

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which is the lowest priority.

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If you want to adjust priorities
for learning processes,

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you can use renice,

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but you can also use top
to nice your processes.

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Let me demonstrate.

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All right, let's start
with this nice command.

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Nice - - help just to
show you how it is used.

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So we can see that nice is worked

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with options and command and argument.

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And the command is - n for the adjustment.

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So - n adds the integer n to the niceness.

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And if you don't do anything,

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the integer that is added is the 10.

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10 means that the process is
becoming the least favorable,

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in terms of priority, because
it's a positive value.

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You want it to have more attention,

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give it an a negative value.

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So if I use

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nice - n - 10 dd if=/dev/zero of=/dev/null

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So if I use nice - n -
10 on the dd command,

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I am getting permission denied.

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Does that make sense?

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Yes, it does.

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Because only user route
can increase the priority.

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So I need to do in order to do that.

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So there we go.

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And oops, I'm running it as
a foreground process now.

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I don't want to do that.

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So control z and bg to continue running it

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as a background process.

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Now I'm going to run
it once more this time

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without the nice command.

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And then we are going to monitor and see

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if we see any differences.

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And this one needs to be a
background process as well.

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Now, how can we best observe

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the differences and
similarities between processes?

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By using top.

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And what do we see?

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We see something interesting.

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And the interesting thing is
that we have two processes,

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and these two processes,
these two nice processes,

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are running with the same priority.

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That's not what I expected,
but it totally makes sense,

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because if you press
one in top, we can see

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that this is a two CPU
system and the dd process can

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run on one CPU at the same time.

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So it doesn't really matter

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that one of these processes
is a higher priority.

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One of them is occupying one CPU,

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and the other one is
occupying the other CPU.

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And you will notice

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that all the other
processes will be running

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on the other CPU as well.

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And that's the result

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of this increased priority
of this one dd process.

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Now you will see the difference,

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if we start one more dd
process, there we go.

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And let's get back to top once more

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because what do we see now?

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We see process with PID 6525,

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which has a nice value of minus 10,

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and which has a CPU priority of 95%.

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And then we see the two other processes,

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the dd processes with
the normal nice value

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and they are running with 47% CPU usage.

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Here you see the CPU usage

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and here we see the nice values.

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So zero is not adjusted.

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Minus 10 means we do have
an adjusted nice value.

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And all this adjusted nice
value influences a priority.

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By default user processes
will learn with priority 20.

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If you tweak the nice value,
then this priority is changing.

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Let me use r, r for renice,
because from within top

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you can change priorities as well.

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I want to renice 6548.

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Notice that I'm running top

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at the moment as an ordinary user,

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and I am allowed to
renice my own processes

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and I'm going to give it a priority 15.

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And what do we see?

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We see that process.

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Oh, it's descending in the list.

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We see that 6548 now as a priority 35,

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nice value of 15, and it almost
gets no CPU cycles anymore.

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And that is how you can use nice

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to adjust process priority in Linux.