For a good linux tutorial, you can see the Software Carpentry Course [here] (https://swcarpentry.github.io/shell-novice/).
Here is a cheat sheet of unix/linux commands that are good to know:
ssh - secure shell, allows you to communicate with another machine.
shutdown — shut down machine.
reboot — restart machine.
exit — exit terminal session.
date — show the current date and time.
whoami — who you are logged in as.
man command — show the manual for command.
df — show disk usage.
du — show directory space usage.
free — show memory and swap usage.
whereis app — show possible locations of app.
which app — show which app will be run by default.