advanced package tool
Favoured by Debian-based distros
apt-get install <package> - just install a package
apt-get update - re-fetch package index files
apt-get upgrade - upgrade all currently installed packages. No packages will be removed, and no new packages will be installed
apt list --installed - list all installed packages
apt-cache policy - list all package repos
apt-cache policy <package> - show where an installed package was installed from, or whether a package is installed at all (useful resource)
apt-cache show <package> show information about a package that isn't installed
Add a line such as the following to
deb [<http://archive.raspbian.org/raspbian>](<http://archive.raspbian.org/raspbian>) testing main
You probably then want to adjust the priority of that repo. For a Docker repo you want to increase the priority so it installs that Docker package; for a testing repo you want to decrease it so it doesn't update all your existing packages!
/etc/apt/preferences.d/limit-testing with a line such as
Pin: release a=testing\\nPin-Priority: 50
Then view your repos with
apt-cache policy, as above.