I started upgrading some of our Etch boxes to Lenny and this is how i did it.
1. Make sure you have installed all updates for the current debian version you are running in our case debian etch. To do this run:
aptitude update and
2. That should update all etch packages on your system. If you run into any missing gpg key problems after running the update please read this aptitude update gpg key problems Then open up you sources list file with you favourite editor.
3. You can either use vi’s great search and relace function or you can add a new list of sources thats up to you. If you use the search and replace function please make sure to check if that archive also offers packages for lenny. The same applies for any custom sources or backports. This is my sources.list file for lenny:
deb http://ftp.debian.org/debian/ lenny main contrib
deb-src http://ftp.debian.org/debian/ lenny main contrib
deb http://security.debian.org/ lenny/updates main contrib
deb-src http://security.debian.org/ lenny/updates main contrib
deb http://volatile.debian.org/debian-volatile lenny/volatile main
deb-src http://volatile.debian.org/debian-volatile lenny/volatile main
4. Upgrade the sources to lenny:
5. Check if you have sufficient hard disk space before you start the upgrade
aptitude -y -s -f --with-recommends dist-upgrade
6. Upgrade aptitude first.
aptitude install dpkg aptitude apt
7. Then do a Minimal system upgrade with
8. Upgrade the rest of the system
After all thats done if you didn’t encounter any problems your done. Before you reboot check you boot loader just to make sure the new kernel is listed on lenny it should be 2.6.26 something then you should be good to reboot.
Source and further documentation Debian handbook