One rather old laptop and one server were the test objects for this howto. Both systems do not have any RAID devices and use a simple partition scheme from a default basic Lenny install. If your setup deviates much from this, it's highly recommended to read all details of the Debian Release Notes before you continue. Be warned. All commands are run as root and Debian recommends to use apt-get for the Squeeze upgrade process. As with all upgrades, begin with a backup of your critical data, and that will be the users data in /home/your-users but I would also back up the content of all configurations files. The latter can quickly be archived: tar -czvf host.etc.tar.gz /etc Move your files for safe storage on a backup drive. Edit your Apt source list file To prepare for the installer, we need to get to a point where the package system is in a clean state. Move the preferences file from the directory if used. If you have a very complicated Debian source file, I would recommend that this is simplified to near the original install. Open up a command line editor and reduce /etc/apt/source.list to something similar to only: [code] deb http://ftp.se.debian.org/debian/ lenny main contrib non-free deb-src http://ftp.se.debian.org/debian/ lenny main contrib non-free deb http://security.debian.org/ lenny/updates main deb-src http://security.debian.org/ lenny/updates main deb http://volatile.debian.org/debian-volatile lenny/volatile main deb-src http://volatile.debian.org/debian-volatile lenny/volatile main [/code] Naturally your country code is likely to be different from mine se. Update the packages for Lenny With a few commands we will make sure that the existing package system is in good shape before the system is upgraded to Squeeze. apt-get update Ready for first upgrade: apt-get upgrade Follow this with: apt-get dist-upgrade Check that no packages are on hold or in any half installed state. The system usually contains many many packages, and before the real upgrade stage we must fix such problem packages. Ensure that we do not have any packages on hold with: dpkg --audit dpkg --get-selections | grep hold No packages can be on hold. For the final go ahead test use: aptitude Press g and the list shows which packages need your attention. Fix any packages in the action list, until the message says: No packages are scheduled to be installed, removed or upgraded Only then you are done and ready to pass this point. Update the source list for Squeeze Update once more the /etc/apt/sources.list: deb http://ftp.se.debian.org/debian/ squeeze main contrib non-free deb-src http://ftp.se.debian.org/debian/ squeeze main contrib non-free deb http://security.debian.org/ squeeze/updates main deb-src http://security.debian.org/ squeeze/updates main and at the command line type: apt-get update Squeeze upgrade in two careful steps It's recommenced to use a two stage upgrade approach with kernel, udev and the preparation for grub2. After the first completed the full distribution upgrade is performed. Start with the upgrade like so: apt-get upgrade Now to the kernel; we need to find your flavor, i.e. the exact version numbers and architecture and install it with: uname -r apt-get install linux-image-2.6.26-2-amd64 If the system is old like my laptop it would install with: apt-get install linux-image-2.6.26-2-686 Prepare grub2 and udev for the new system: update-grub apt-get install udev Once previous steps have completed, it's time to restart the system: reboot Almost there When the system has restarted, continue with the full upgrade phase: apt-get dist-upgrade Starting the system with the first menu item shows if grub2 works properly, if so run: upgrade-from-grub-legacy which will install grub2 in the Master Boot Record (MBR) on the disk. Further information are found on Debian main site. Via Howtoforge