Ytdyklly

There's a saying in my language which can be roughly translated as "You can't turn mince back into meat by rotating the mincer's handle in the opposite direction" :)

The upgrade procedure is one-way - while installing new versions of software, your configuration files and settings are modified by packages' post-install scripts to use new format which is required by new software. Basically, there's no opposite procedure - to make a newer configuration file compatible with old software.

It's possible at the level of the packaging tools (apt). But the resulting system may not be equivalent to doing a reinstall, and you may get errors along the way. This is because many packages contain specific support for upgrades (e.g. handling changes in configuration files) but not for downgrades.

Normally, apt prefers to install the most recent version of a package. But you can change this through pinning: you can declare that packages from the old release have higher priority than the installed packages, so that they will be downgrades when you do aptitude dist-upgrade.

Change your /etc/apt/sources.list to include only the old release (either edit the file or use your favorite GUI), and run aptitude update. Then edit /etc/apt/preferences (documented in the apt_preferences man page) and add the following lines (to downgrade to lucid):

Package: *

Pin: release v=10.04

Pin-Priority: 1001

Then run aptitude dist-upgrade. Every package has a priority greater than 1000, so every package that is present in 10.04 and installed on your system will be downgraded. You'll have to remove packages that weren't in 10.04 manually; they'll be listed under “Obsolete and locally created packages” in aptitude.

They say, "never say never", and "nothing is impossible" - both of which are true, but not in your case. I suggest you either back up your data and reinstall, or stick it out. The system should become more and more stable as the weeks go by.

You can also reinstall on top of the existing installation (it will keep your files).

As a rule of thumb though, try to avoid upgrading to development versions on production systems (especially if you are not a tester/developer).

You can do it manually.

First generate a list of what you have installed on your system. You can do this by typing the following in the terminal.

sudo dpkg --get-selections | grep '[[:space:]]install$' | awk '{print $1}' > package_list

copy your /home and /etc folder to a backup media.

Re install ubuntu 10.04. Restore your backup (remember to set the correct premissions). Then run the following to reinstall all the program you had before.

cat package_list | xargs sudo apt-get install

Note that you might have to do some cleaning of the /etc and /home folder for incompatible settings.

This is why you are not supposed to upgrade your main install to the development release. If you want to test the development release, you should do so on a separate partition so you can boot back into the stable release when things go wrong.

At this point if you want to go back to 11.04, you need to reinstall it, and choose manual partitioning. Do NOT check the format box when configuring your partitions and your user files should remain intact.

Simple method is booting up from a CD/DVD or USB stick of previous version and reinstall Ubuntu by overwriting existing installation.

Don't forget backup first: your home directory any anywhere else you may have personal data.

Roll-backs may work fine for certain packages in isolation, but I wouldn't ever expect a large-scale roll-back of an entire distribution to leave you with anything other than a horribly broken system (or one which, on the surface looks to be fine, but strange things keep surfacing as you discover it is more and more broken).

APT is just designed to avoid roll-backs as much as possible, and the packages that make up the Ubuntu (and Debian, for that matter) distribution aren't designed with smooth roll-backs as a design goal.

Unless you have whole-system backups that are reliable, what you really need to do is ensure your entire home directory is backed up (and possibly also on a separate partition), re-install from the CD image of your chosen version, and start restoring your data from your home folder(s). You may even need to selectively restore the dotfiles in your home directory in case any which have become accustomed to the new version don't quite work well with the older version.

Before you do, you may want to peruse your installed packages and write down which ones you rely on, so you can re-install them. There are tools to backup and restore your list of installed packages, but I wouldn't normally recommend doing this if you are going between versions as the packages needed/included may have changed.

To put it simply: no there's not. Sorry... (These are the dangers of upgrading to testing releases!)