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Hello again, and now, in this lesson, we

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are going to cover process management.

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What is a process management?

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Anything that has to do with the process, how

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we manage it, how we start it, how we

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stop it, and how we bring it in the

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foreground, how we bring it in the background,

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all that stuff is process management.

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Let's go over all the commands

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that are associated with managing processes,

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the first one, are the set of commands that

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we have, for putting a process in the background.

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So why do we need to put a process in the background?

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Let's talk about that first.

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When you run a process on your terminal, meaning when you

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open up a console or when you open up a PuTTY

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terminal, when you run a process on your terminal, it will

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run it and it will not give you your prompt back.

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So if you want to do certain other tasks or you

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want to exit out of it, it will stop your process.

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So how do you run it in the background?

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So the command is Ctrl-z.

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First you run the process, then type

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Ctrl-z, it will stop the process,

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then you type jobs to list what is being stopped,

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and then you type bg, which is

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to put the process in the background.

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Then we have Foreground.

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So if you are done with all other tasks that

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you're doing on your terminal and you want to bring

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the process that you had put in the background initially

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and you wanted to see the process of it, then

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you type fg for Foreground, and that process will become

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live again on your console.

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To run a process even after you exit, meaning

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if you exit or if you close your terminal

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while your process is running, what will happen?

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It will stop the process.

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So how do you prevent it?

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There's a command called nohup.

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It means don't send any kind of signal to stop it.

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So nohup, the process, and followed by the

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sign ampersand or and sign, which is on top

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of your number seven key on your keyboard.

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Another command for that is nohup, the

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process, and redirect sign, /dev/null, and two,

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redirect, ampersand, one, and ampersand

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again. Why do we have all that stuff there?

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Because certain times when you run certain commands,

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like nohup, it gives some kind of

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warning, some kind of information about that process.

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So you don't want to see that.

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You want all that garbage to go out to /dev/null. So

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/dev/null is kind of an output to a

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door that you don't want to see the output for.

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Then to kill a process by name,

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you guys already know how to kill

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a process by process ID, right?

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So you kill, followed by the

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process ID kills the process.

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What if you want to kill a process by its name?

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So let's say if you have a process called top, right?

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So you run the command top.

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If you want to kill it by the name, you

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just simply type pkill, followed by the name of

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the process which is top. Process priority nice,

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there is a command called nice.

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And why do we use it?

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Because if we want to prioritize

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by different level of process.

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Meaning if a process is very important then the other, it

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has to be prioritized right. So the niceness scale goes from

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-20 to 19. The lower the number the more priority that

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task gets. Now why do we really need to go with

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the priority of the task, doesn't that processor CPU takes care

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of that, right, it does take care of that.

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But remember one thing. If you have one

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CPU in your computer or laptop, it means

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it will process one program at a time.

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So think of it as a juggling.

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So if you have two hands and you have five

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balls to throw it in the air, what will happen?

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Can you hold all five balls in your hands? No, right.

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So think of balls as programs that you need to process.

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So you would have to juggle it one after the other.

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So what nice does is, nice tells hey, this ball or

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this process is important to me, so make sure this stays

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in the hand most often than any other balls.

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So that's what nice does.

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We'll talk about that when we open up

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our terminal session. Then how to monitor a process is

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by running the command top and how to list all

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the processes that you have running in your computer,

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the command is ps, followed by of course

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many different options that you could use.

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So anyway, let's get into our Linux machine.

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I have it open right here, our console.

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So I am logged in as myself.

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I want to become root.

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So become root.

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Now I want to log into the PuTTY section as well,

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so this way I could run certain different programs from one

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terminal and kill it on the other terminal. So for that

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to log into the PuTTY, what do I need?

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I need an IP address of my machine.

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The command is ip addr, or ifconfig whichever you prefer.

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But if you're running latest version of Linux, then

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you probably not going to have ifconfig, so run

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ip command, and the IP address you'll see right

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here it says 192.168.56.101.

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So go into your PuTTY terminal.

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I have my PuTTY terminal right here, and I'm going to type

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it in my IP address which is 192.168.56.101.

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Hit enter, login as root.

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The first one is Ctrl-z.

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So I'm going to run a command called sleep.

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sleep is a command which will delay certain programs.

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Let's say if you're running a program ABC, and you wanted

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to run a second set of program, but you wanted to

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wait for 10 seconds, so you put in a sleep command.

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That's what it does, it just waits for 10 seconds,

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and it goes to the next set of instructions.

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So let's say if I type sleep 5, it will wait

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for 5 seconds, until I got my prompt back.

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You'll see, I got the prompt

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back right away after 5 seconds.

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So that's what sleep does.

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Don't focus too much on sleep, focus on what

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I'm going to teach you about process management.

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So I'm going to leverage this

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lesson on the command sleep,

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so this way it will be easier to understand.

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So if I run the command sleep 100, what will happen?

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I will have to wait 100 seconds

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until I get my prompt back, right?

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So I want to run that process in the background.

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So I will do Ctrl-z, it has stopped the process.

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Now it's not running actually in the background.

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To run that in the background, you have to

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type the command bg, which is for background.

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But let's say if you are running multiple process, and

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all of them stop, some of them are running.

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So the command to check what other

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processes that are stopped right now,

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so you just type command jobs, and you

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will see there is one process that's been

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stopped by the command Ctrl-z.

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If you want to run that process, bring

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it and send it to the background,

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then you type bg.

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This will send this process in the background.

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See, it is running now.

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So when you type jobs, you'll

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see right here, it's not stopped.

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See, it's running, but it is running in the background.

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You could also check by ps -ef command, by typing sleep.

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And you'll see right here, sleep 100.

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The other sleep 60,

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you could ignore that, this runs all the time

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if you're running virtual machine.

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Anyway, sleep 100 is still running.

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What if you want to bring it

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in the foreground, then you type fg.

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See, it's brought back that process in the foreground.

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And now you notice I do not have my prompt back. Why?

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Because the process is still running.

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So what if I wanted to put it back in the background?

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Okay, so 100 seconds are done.

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I got my prompt back.

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If I wanted to put it back in

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the background, I would have type Ctrl-z. Okay?

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Now, the next one we have is about nohup process.

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What is a nohup.

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Well, nohup is if you run a

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process and then you close your terminal.

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Meaning this terminal, if I close it right now, let's

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say if I'm running a command sleep 100, it is

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going to run, or it's going to wait for 100.

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Now, if I go to my console, clear the screen

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and I type ps -ef and do grep sleep,

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you'll see the sleep 100 is running, right?

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So if I wanted to,

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[No audio]

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have this terminal, let's close

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this terminal, I have a couple of terminal open.

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So if I close this and then do ps -ef sleep,

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now you'll see both sleep 100 are gone.

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So every time you run a process,

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it attaches itself with that terminal.

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Now, how do we run a process without

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interrupting that process when we close a terminal?

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So, let's go to our PuTTY session

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again, to run a process in the background and when you

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close the terminal, it won't impact it, you run nohup,

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[No audio]

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and name of the process, which is sleep 100,

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[No audio]

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let's put a sleep 75 just to differentiate it, and ampersand.

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So you hit Enter, and you will see,

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now it's running that process in the background.

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So when you do jobs and you'll see

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it is running, but it is not impacting

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your terminal, it's not attached to your terminal.

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So even at this time, if you

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close it, this process will still run.

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Now, what about this, nohup:

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ignoring input and appending output to 'nohup.out'.

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Well, every time you run a nohup command,

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it actually creates a file called nohup.out.

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So what it has, it has all the

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information, all the things that you have typed

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in there, it will just record everything.

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But if you just don't want to see that message comes

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up on the screen, or many times when you run certain

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commands, it gives you a message that this command was created

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on this day, and so many other stuff.

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So to get rid of that message, you could

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type nohup sleep 73 just to differentiate again,

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greater than sign, /dev/null, two,

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greater than sign, ampersand, one, ampersand again, hit enter.

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And now you will see, you did not get

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all that stuff that you were getting it before.

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Because what we are saying is whatever that comes up

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on the screen, those error messages, a warning, or those

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even informational messages, just send it to /dev/null,

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don't send it on the screen.

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So send it in the back.

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Now, what if you want to

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see what's running in the back?

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We run jobs and you'll see this

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one process is running in the background.

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Now, again, what if you wanted to bring

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that process in the forefront in the foreground?

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Just type fg, and you'll see it is running and

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it is on the foreground and you will not get

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your prompt back until it waits for 73 seconds.

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Once it's finished in 73 seconds,

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then we'll get a prompt back.

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Anyway, let's Ctrl-c out of it, which

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will completely stop, because if you type jobs

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now, you won't see any jobs.

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The next lesson, or sorry, the next topic

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of this lesson is about process priority.

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Which means run a process with a certain priority.

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So you could just simply type nice, space,

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-n, and space, what's the priority

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you want to give it, -20 which is the

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highest one, no I don't want it to mess

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up my other processes in the system.

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So I'll just say, simply say five

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and then I'll do sleep -10.

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I hit Enter.

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Now what it's doing

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is, it's telling CPU, hey, CPU I have

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this process sleep ten and please give this

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process priority five, which is not too high,

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which is not too low,

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it will tell that to the CPU, and CPU will process

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that according to the command of nice, that's what nice is.

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If you want to run your process to be the top

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priority it is very important, then I would say run nice

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-n -20, the name of the process, hit enter, and

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CPU will say hey, that's it, I have nothing to do

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but to take care of this process right away.

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That's about the nice of the priority.

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The other ones we already covered, which is the process

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monitoring, and of course the list of process to see

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what other processes are available in the system.