IntelliJ IDEA: How to Permanently Turn On Line Numbers

How to permanently turn on line numbers in IntelliJ IDEA (and other JetBrains IDEs):

1. Go to File > Settings...
2. Then go to Editor > General > Appearance.
3. Check the Show line numbers box.
4. Click Apply and OK.
5. Line numbers are now permanently turned on.

Video: https://www.youtube.com/watch?v=uLRh_z40lLE