Warning: There are two commands mentioned in this how to, both that require double dashes – – but for some reason WordPress is not rendering that correctly. After each dpkg hit space and hit the dash button twice. Sorry for the the inconvenience.
A clean install or an upgrade? That’s a question that keeps tossed around every new Ubuntu release. Common wisdom would suggest that a clean install would probably be better, however the inconvenience of losing current installed apps and configuration makes most of us shy away from this path. But what if I told you that you could have the good of both worlds? A fresh install and keeping your apps and configuration intact?
Configuration
Keeping your configuration intact is pretty straight forward and obvious. Just backup your /home folder onto an external drive or whatever. Make sure you also grab the hidden files, don’t do my mistake!
Crap! My backup of /home didn't include hidden files! Now I lost all my configuration!!
— Rami Taibah (@rtaibah) November 10, 2008Applications
Now for the current applications. Basically we just need to make a full list of the installed apps.
sudo dpkg --get-selections \> /home/user/package.selections
Of course don’t forget to backup package.selectionson the external hard-drive. Also you should backup your /etc/apt/sources.list file since you probably have some extra sources listed over there. Now you can go about your business and do a fresh install.
Restore
Once your done with the fresh install, copy the file* package.selections* into your home. Then copy your sources.list file into /etc/apt/ and update it to match your current distro (e.g Gutsy –> Intrepid) you can use CTRL + H in gedit for that. Then do a “sudo apt-get update” ,and finally invoke:
sudo dpkg --set-selections /home/package.selections && apt-get dselect-upgrade
apt-get will now start downloading all your apps, this will take some time depending on the number of apps you have installed.
Once that’s done, just copy your backup-ed /home over the current /home (again don’t forget hidden folders).
Log out and log back in to your shiny new fresh install!
Edit: As the commentators below also mentioned, it would also be wise to have your /home in a seperate partition (thanks Boo Radley), back up /etc (thanks Bartek), and use the tar command to back up home (it will preserve your structure and permissions)