Some warnings before you start: Back up your system! The following steps are only recommended for those, who know what they do with their command line terminal. And everything you do – you do it on your own risk!

• Problem 1: I use apt-get instead of aptitude … but you should not use both systems at the same time!
• Solution: You can just use apt-get instead of aptitude. So the commands are:
  
$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get install update-manager-core
$ sudo do-release-upgrade

  Be sure NOT to restart at the end of the upgrade … see problem 3 why!
• Problem 2: The do-release-upgrade script starts but aborts by telling me that I don’t have enough diskspace on my boot-partition:
  
The upgrade aborts now. The upgrade needs a total of 52.4M free space on disk '/boot'. Please free at least an additional 18.1M of disk space on '/boot'. Empty your trash and remove temporary packages of former installations using 'sudo apt-get clean'.

• Solution: Start to clean up your packages by using the suggested command:
  
$ sudo apt-get clean

  … but this was not enough on my server. So I figured out that I have a bunch of old kernel versions on the boot partition – which also can be removed. Check which kernel versions are installed by using the following command:
  
$ dpkg -l | grep linux-image

  In my case, I was able to delete the old linux-image-2.6.15-29 and the linux-image-2.6.17-12. Be sure to keep at least the Gutsy Gibbon version!
  
$ sudo apt-get remove --purge linux-image-2.6.15*
$ sudo apt-get remove --purge linux-image-2.6.17*

  Then you need to update your menu.lst:
  
$ sudo update-grub

  After doing this I check the kernel list file by looking into the file with the vi-editor:
  
$ sudo vi /boot/grub/menu.lst

  If everything looks right within the automatic kernel list at the end of the file I go on.
• Problem 3: The Ubuntu-geeks solved thisone themselves, but when I upgraded from Feisty Fawn to Gutsy Gibbon, I ran into big trouble: The do-release-upgrade functioned well, but when I restarted the server it did not boot properly anymore! The kernel list was not setup properly by the do-release -upgrade script!
• Solution: Therefor I always finish the do-release-upgrade script without restarting the server;
  then I re-update the menu.lst by
  
$ sudo update-grub

  after doing this I check the kernel list file by looking into the file with the vi-editor:
  
$ sudo vi /boot/grub/menu.lst

  If everything looks right within the automatic kernel list at the end of the file.
  
$ sudo restart


When you are finished with the upgrade and restarted your server … you should be able to access the server again via ssh. Then you can check the version of the installed linux version by typing:

$ lsb_release -a

The result should look like this :

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 8.04
Release: 8.04
Codename: hardy

I hope this howto / problem solving saves some time for you