I need some help upgrading. I'm trying to upgrade my Ubuntu server 11.04 and it's failing with the following message:

root@li220-189:~# do-release-upgrade
Checking for a new ubuntu release
Your Ubuntu release is not supported anymore.
For upgrade information, please visit:
http://www.ubuntu.com/releaseendoflife

Get:1 Upgrade tool signature [198 B]
Get:2 Upgrade tool [1471 kB]
Fetched 1471 kB in 0s (0 B/s)
authenticate 'oneiric.tar.gz' against 'oneiric.tar.gz.gpg'
extracting 'oneiric.tar.gz'
WARNING:root:estimate_kernel_size_in_boot() returned '0'?

Please report this as a bug and include the files /var/log/dist-upgrade/main.log and /var/log/dist-upgrade/apt.log in your report.

The upgrade has aborted.

Running:

apt-get --purge clean

before doing the upgrade did the trick. Maybe just lucky but we now have our server up to the 12.04LTS