How can I use an old Ubuntu distribution with repositories?

The repositories for older releases that are not supported (like 11.04, 11.10 and 13.04) get moved to an archive server. There are repositories available at
The reason for this is that it is now out of support and no longer receiving updates and security patches.
I would urge you to consider a supported distribution. If your computer is too old in terms of memory or processor then you should consider a distribution such as Lubuntu or Xubuntu.

If you want to continue using an outdated release then edit /etc/apt/sources.list and change and to
You can do this with sed: sudo sed -i -re ‘s/([a-z]{2}.)?|’ /etc/apt/sources.list
sudo apt-get update # && sudo apt-get dist-upgrade