Fixing repository sources in old linux distro [Ubuntu and its forks]

You've decided to run an old linux distro on your machine and you find you can't install anything because of outdated repository information.

sudo apt-get install vlc


Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package vlc


You'll need to edit /etc/apt/sources.list and change 'archive.ubuntu.com' to 'old-releases.ubuntu.com'. This can be achieved with sed.

sudo sed -i -e 's/archive.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list

Then update with sudo apt-get update

You should be able to install new applications from repositories.

[Source.]