Free

See free space with:

free

and make it human readable with:

free -h

Or -m for megabytes.

Proccesses

See running items in current terminal with

ps

or more with

ps -a

Or the entire system with

ps -e

Or the entire system with more information, BSD style, with:

ps aux

And then search for a particular program with

ps aux | grep cmus

Pause a job with ^z. Put it in the background with the '&' suffix.

List jobs in the current shell with

jobs

And then you can pull number 1 up again with

fg 1

Or continue running a stopped job with:

bg 1

This changes how nice a program is, from -20 to 19.

Install a program, but nicely, at nice value '10':

nice -10 sudo apt -y install libreoffice

Aggressively use Steam, with a nice value of '-13'.

nice --13 steam&

Find out that Steam's fucking everything up, so you change its nice value with 'renice':

renice --5 -p 3781

Nerf all of roach-1's processes:

renice 10 -u roach-1

... or the entire group

renice -14 -g hackers