Update your system

Arch Linux based systems

You can fully update/upgrade your main system by using pacman. Keep in mind, it does not include AUR

$ pacman -Syu

If you want to include AUR - Arch User Repository Packages installed, you have to use an AUR Helper. In my case I use yay:

$ yay -Syu

The -S option tells pacman (or yay or any other AUR Helper) to synchronize the local database with the main repository database.
The -y option updates the local system cache.
The -u tells the package manager to actually upgrade the packages.

Basically, this whole command synchronizes the local pacman database with the main repository database and then updates the system.

When installing packages in Arch, avoid refreshing the package list without upgrading the system.

In practice, DO NOT run pacman -Sy package_name instead of pacman -Syu package_name, as this could lead to DEPENDENCY ISSUES.

You can perform a full system update/upgrade by running this combination of commands:

$ sudo apt update && sudo apt upgrade -y

The apt update option updates the local cache from the Debian repository to check for new available versions of the installed packages.
The apt upgrade is the command that actually updates your Debian system.
The -y option let the apt upgrade command to run automatically after the first command finishes successfully.