To begin, edit
/etc/apt/sources.list and change all occurrences of lenny to squeeze. A quick vi macro if you use it would be
%s/lenny/squeeze/g. Once finished, you file should look similar to the one below.
# main repo deb http://ftp.debian.org/debian/ squeeze main deb-src http://ftp.debian.org/debian/ squeeze main deb http://security.debian.org/ squeeze/updates main deb-src http://security.debian.org/ squeeze/updates main
Next we'll update the package lists:
Before we can finish with the dist-upgrade, we need to update core system utilities that will be used during the dist-upgrade.
apt-get install apt dpkg aptitude
Finally, once this has completed, the following command will complete the software update part of the task:
This will bring all of your system and installed packages up-to-date with the current release of Squeeze. Any third-party .debs installed from non-standard sources or by hand will need to be updated/reinstalled manually.
The installer will ask you if you want to use Dash, and unless you have a compelling reason not to, we recommend you choose to use it.
Any service restart prompts during the process are normal and typically take less than a few seconds. If an error is detected, the installer will attempt to fix it for you, or provide the error. It will typically restart SSH as well, but do not fret, it will keep your session active!
There is no need to make any kernel or grub-related changes unless you are explicitly running a pv-grub kernel (hint: most users are not), and in fact neither of these need to be installed. When the installer asks you about these (such as grub install devices), you can just skip/breeze right through them.
Squeeze does not appear to boot properly on 2.6.18 kernels, so ensure that you have selected a 2.6.3x or newer kernel.
Reboot your VPS as normal to bring it up on the new kernel and make sure all of your services started OK!