Introduction to Linux in HPC/Processes

This tutorial covers the basic principles and treatments of processes in the multi-user operating system Linux. It will explain the viewing (and killing) of processes with a text-based process manager and the execution of processes in background/foreground.

Video

( Slides as pdf)

Quiz

What does PID stand for?

	Packet Identifier
	Process Identifier
	Protocol Identifocation

How are the permissions of a process set?

	By inheritance of owner's permissions.
	Manually by user
	Explicitly at startup by parameters.

How are the permissions of a process set?

Assign the commands their correct meaning

pstree	top	fg/bg
			... overview of running processes and sub-processes
			... sending processes to foreground/background
			... text-based task manager

Exercises in Terminal

1. Start a process, bring it into background/foreground.

Hint:

     To bring a process to background:
        Press Ctrl-Z (pause the process).
        Type bg (bring it to background).
     To bring a process to foreground:
        Display running "jobs" and identify the job ID: jobs
        Type fg <job-ID> (bring it to foreground).

2. Start the task manager and identify the process with the largest memory usage.

Hint:

     Start the process manager: top
     Activate highlighting for current sort column: press 'x'
     Select column to sort for: press '>' or '<' until column '%MEM' is acitve
     (optional) Reverse sorting: press 'R'

3. Start the task manager and filter processes of your user account.

Hint:

     Start the process manager: top
     Select username to filter: press 'u' and type in username

4. Start a process (e.g. sleep 10m) and kill it from a second console.

Answer:

     Start the process: sleep 10m
     Go to a second console.
     Start the process manager: top
     Filter process from your user account: press 'u' and type in your account name.
     Identify the job ('sleep') and note the associated PID.
     Kill it: press 'k' and type in the PID from previous step.

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