- In this video, I want to explain Linux processes and jobs.
Anything that runs on Linux runs as a process,
and processes have a process ID, and they can be managed
by sending signals to it.
Signals are special operating system instructions.
There is Sigterm, also known as Signal 15,
which is a default signal that instructs a process to stop.
There is Sigkill or Signal Nine,
which is a signal to force a process to stop immediately.
I'll tell you how to do that later in this lesson.
Then there are jobs.
Jobs are user processes that have been started
from a specific shell.
And the nice thing about jobs is that users can manage
their own jobs.
And all processes originate as child from systemd.
Let me make a drawing to show you how this is organized.
- In this video.
I would like to explain a little bit
about processes and how they are hierarchically organized.
So it all starts with systemd.
Systemd is PID One.
It's a model of all processes.
And you will notice that all other processes are a child
of Systemd.
You'll find kernel processes between square brackets.
If you use a command like PSX, for instance,
you'll find your service processes
like your SSHD, and you'll find many, many more.
And then at some point, there will be the gnome terminal.
The gnome terminal is a process that is typically started
for a graphical terminal.
And as a child of this known terminal,
there is bash, and bash is your shell.
Now, if in this shell you are running commands,
like a command, let's say, sleep 60,
which will sleep for 60 seconds,
or ls-l.
All of these are children of the bash shell.
They are a part of the process tree.
And because they are a part of the process tree
you can manage these as processes,
but if they are your own, then these are the one
that can also be managed as jobs.
In the next couple of lessons,
I will show you how to manage these processes
as well as the jobs.