Learn Linux with Free Lessons & Tips

Permissions in Linux 

rwx|rwx|rwx   =user | group | others

R==4

W==2

X==1

what's the total?

421|421|421

777

So 7 has 4, 2,1==which means full. Permission (that is read write and execute)

So it means u + g + o == got full permission 

What is a Process

An instance of a program is called a Process.

Any command that you give to your  Linux machine starts a new process.

It is possible that for the same program we have multiple processes.

Types of Processes

• Foreground Processes

• Background Processes

Processes in action

Process  running on system are actions running on system.

Jobs are specific to a user for that given shell where it is been run.

You can check the number of processes running by using command,

 ps aux

And also get the count of total processes by using command,

 ps aux | wc

A job run by user or root is specific to his profile and for that given shell.

It has nothing to do with system processes running.

Example,

You can write a job specific to shell, like,

 dd if=/dev/zero of=/dev/null

This job does nothing and shows nothing.

Input file - /dev/zero

Output file - /dev/null

Every command that we start from a shell is considered a shell job.

If we type command ls

So, this is shell job.

 They start and stop immediately since they have done their work.

 Hence it is important to know the difference between a job and process.