Updates

Fix the repositories:

1. sudo nano /etc/apt/sources.list
2. Remove the "#" from the start of each repository. This will uncomment them and make sure that they're included the next time you update.

Set up automatic updates:

1. sudo apt install unattended-upgrades (this will most likely be preinstalled)
2. Ensure that it's configured correctly. run the command "sudo nano /etc/apt/apt.conf.d/50unattended-upgrades". Find the line that says "Unattended-Upgrade::Allowed-Origins", and look inside of its curly braces. Uncomment any lines including "${distro_codename}", but keep lines that end with "-proposed" or "-backports" commented. This will ensure that only security and recommended updates will be installed.
3. sudo nano /etc/apt/apt.conf.d/20auto-upgrades. Set each line equal to "1" (with the quotation marks). This will tell it to update and upgrade each day.
4. sudo systemctl enable unattended-upgrades && sudo systemctl start unattended-upgrades