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In this video I'll tell
you about processes and jobs.

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Anything that runs on
Linux runs as a process.

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And if processes get stalled or are creating trouble in any
other way, you need to know a little bit about process management.

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First thing to know is that the process has
a process id, also known as a pid, and it

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can be managed by sending signals to it using
the KILL command. Signals are special operating system level instructions.

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SIGTERM is a normal signal that instructs
a process to stop and Sig kill

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or signal 9 is a signal
to force a process to stop immediately.

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Jobs are user processes that have been started from a
specific shell. All processes originate as children from systemd. Let

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me make a drawing so that I can explain
the relation between the different types of processes on Linux.

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Okay, so how are
processes created on Linux?

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Well, it all
starts with the kernel.

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The kernel refers to systemd,
and systemd is PID number one.

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It's top of all processes. It's
the start of the process hierarchy.

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Now systemd is going to start multiple processes
and many of these processes are the services.

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These services are also
referred to as daemons.

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A daemon is daemon, like
the HTTPD daemon. That's a service

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that is making sure that
functionality is provided by your server.

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Now, a process by itself is manageable
using its pid. Processes might be multi threaded.

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And if a process is multi threaded, it can
be serviced by multiple CPUs at the same time.

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Now, somewhere in the process hierarchy there's also
your graphical user interface where you or your

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shell. But let's talk about the system that
we are using here, where at some point

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you'll find gdm, the GNOME display manager.
From this GDM you have the GNOME shell.

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You might not exactly find it as GNOME shell,
but this GNOME shell is a graphical user interface itself.

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And in this GNOME shell
you start your terminal window,

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and in this terminal
window you start your shell.

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And that is where we are at the
location where Bash is used. This is the

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location of the individual user if an
individual user is going to run any tasks.

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These tasks are manageable by the
user as jobs. In the next couple

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of videos you'll learn how to
work with these daemons, processes and jobs.