Ubuntu EOL (End-Of-Life)

If you only need access to some old repositories the only step you need to apply is adding/editing few lines in /etc/apt/sources.list.

## EOL upgrade sources.list
# Required
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-updates main restricted universe multiverse
deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-security main restricted universe multiverse

# Optional
#deb http://old-releases.ubuntu.com/ubuntu/ CODENAME-backports main restricted universe multivers

Now just execute apt-get update and you can use those repositories.