Linux Sysadmin Basics -- 6 -- Processes Overview

What are processes in Linux? What's the lifecycle of a process? What important attributes does the Linux kernel track about processes, and how can I start peeking under the delicious, Linux-y covers?

All of this (and so much more!) will be covered in this unit about processes. This video is the overview that will get you started.

[Thomas-yvyw]

This one was really hard to follow so I had to take notes, it's not that complicated.

PROCESSES :
basically a program that runs

"has 2 parts" :
1. adress space that it can use, where it can write to
2. kernel data structure keeping following information :

* PID : primary key for processes
* parent id : pid of process that started this one, if parent dies then child process is reparented to "init" process
* UID : tells which user owns the process (same for groupID)
* EffectiveUserID : (EUID) process spawned by user but shouldn't have same permissions as user (same for EgroupID)
* Niceness : if NI high then it's low priority and let's lower NI processes take resources

Life cycle of a process :
created by parent process by forking itself,
giving child that starts other programs/processes
death : exiting with return value given to parent process

case of init: (for ubuntu)
started at kernel boot, runs all startup scripts

[DmitryFromForest]

That was unexpectedly emotional. Processes that are done tell the kernel, it kills them and notifies their parent. Man, thank you so much for all these videos. I'm so glad I stumbled upon your channel! I'm genuinely enjoying the way you explain things.

[ivanhornak]

"so init is sort of the mommy for all the processes whose parent's have died" :D

[moijafcor]

pstree is a great command to visualize in a tree view parents processes and their children. If the list overfloods your console, pipe it up to less for scrolling and pagination: pstree | less

[CustomNameHere]

Great series!
Could you please do a tutorial on the Linux boot process?
Much appreciated.

[robindoermann]

We're inert deterministic processes too, buddy!

[DarkWhisperer]

Could you do like a video on a SysAdmin every day's Tasks? Please...

[PunmasterSTP]

Processes? More like “Perfect video this is!” Thanks for another banger.

[info]

You kinda lost me on this one when you started talking about stuff that's not on the screen. I kept expecting to find out that you were giving the definition for PID, User, Pri, Ni, VIRT, etc.

Still good to know. I just don't think I retained much of it....

[thequalizer_ttv]

What’s more good practice for someone just entering the field. I want to learn more information!

[Ulghart]

Well, init is now in the past. Every distribution has switched to systemd as far as I am concerned.

[SakosTechSpot]

So the parent forks itself and creates a child. I get it now!

[Ulghart]

I always used nmon in unix systems. Linux doesn't have it but it can be installed, so I did. I still think that is more detailled than top and htop. Have you ever used it ? What's your opinion?

[mrthomasfritz]

What is the difference between a zombie process and an orphan process?
A zombie process is not the same as an orphan process. An orphan process is a process that is still executing, but whose parent has died. They do not become zombie processes; instead, they are adopted by init (process ID 1), which waits on its children.

[jonassteinberg]

process: an instance of a program in memory

[suhanguo]

thank you for the videos, they're super helpful. I'm wondering if you have any recommendation on how to practice Linux commands, say if there are practice problems I can access?

[stefanspinu]

You said you can see the parent ID of a PiD, but never said how to... so how can we see the parent ID?

[abdelrahmannawar]

so should I watch the rest of the processes videos ? as ubuntu now uses systemd ?

[Shvmadogg]

Have you tried freeBSD before and if so, what are your opinions about it?

[malikfaseeh]

fork() execlp(), exit(), and wait() system calls please make video about these commands.