Processes and jobs, before we get into this lesson, I want you to understand what exactly each term
means in the Linux environment.
Well, first we have applications which are also referred to as service, an application or a service
as like a program that runs in your computer.
And then application could be anything like in Windows.
You have Microsoft Word, PowerPoint and Linux.
You have programs or applications like A.P. and EF-S, Apache and a whole bunch of different programs.
So that is an application and service that runs on your computer.
Then you have a script.
What exactly a script is a script is something that is written in a file and then packaged it to in
a way that it will execute.
So any application that is running in your computer, for example, Apache, you would have to run that
as a script and that would run in the background.
So that's actually a script and also all those different commands that we run in a Linux environment.
All of them are also referred to scripts.
Then we have a process.
What is a process?
When you run an application or when you start up an application, it actually generates a process where
this process ID now processes could be one associated to that application, or it could be multiple
processes.
Then we have Damon.
The daemon is I could tell you when I compare it with the process is something that continuously runs
in the background or it doesn't stops.
So when you run a demon, which is also a process, but it keeps on running the background and it keeps
listening to the incoming traffic or outgoing traffic.
Then there is a thread on threads, every process could have multiple threads associated with it.
An application that is running in your background, let's say an office when you run that application
in your Linux machine.
It could have many multiple threads if a machine, a remote machine, tried to connect to you through
an office.
It will generate one thread for it, and it will generate a second, third or third thread for other
computers at attaching to it.
Then we have a job, a job as something that is created by scheduler like a work order to run those
applications and services and process and service commands.
We have a first command, a system.
Seitel This command is now choosed in Red Hat.
And it is being replaced.
So there were the old command that was running an earlier version of Red Hat or Centaurs, a service
service is now being replaced with a newer command system, CTL.
Then we have a Pia's command.
This command allows you to see what are the processes running in your Linux system.
You could use two different options with that to find out exactly the process that you are looking for.
Then you have a top command.
Now, when you run the top command, you will see all your processes running in your system, depending
on which process you wanted to see first based on its load.
And it also tells you your memory information, CPU information that is being used by that process.
Then we have a kill command.
The kill command kills the process it kills by the process name or kills by the process ID.
So when you start an application again, going back to our example of Apache, when you run an application
FTP, which associated with Apache, it has a process ID to would.
You could stop that process by running system.
Ctrl stop.
Or you could simply kill, followed by the process name or process ID will cover kill.
Come out later.
And this lesson then we have crontab.
Crontab Command is used to schedule these these applications or this process or these services for you
in your system.
You will run crontab at minus e to edit it, and there are different options, a little color with the
crontab.
So when that crontab, when that process or application is scheduled in crontab, that becomes a job.
And the last command that will cover is act at command is just like crontab.
The only difference between add and crontab is at a schedule as one time basis or as an ad hoc process.