Add a new user (with supporting info)
	$ adduser userid
	follow prompts

Login a terminal as another user
	$ su userid

List users & groups they're in
	$ groups
	$ groups userid

Add/delete group
	$ sudo groupadd group
	$ sudo groupdel group

List groups (& members in)
	$ getent group
	$ getent group group

Set a user's secondary group(s)
	$ sudo usermod -Ggroup(s) userid
Append to a user's secondary group(s)
	$ sudo usermod -a -Ggroups userid
Set a user's primary group
	$ sudo usermod -ggroup userid

List directory contents with permissions
	$ ls -l
List directory recursively
	$ ls -R

Change file permissions / user owner / group owner
	$ sudo chmod options permissions filename(s)
	$ sudo chown userid filename(s)
	$ sudo chgrp group filename(s)