It just so happens I recently migrated a linux system from ext4 to btrfs and didn't want to do a fresh install. So make a new partition, format it and copy the system over... Too bad I forgot to tell 'cp' to preserve the file permissions. I ended up with a system where every last file was owned by root and that obviously causes problem with everything that isn't executed as root. And of course, the old partition was already gone - bad luck. Reinstalling is pretty much the only 'solution' I could find for this problem on the web. What follows are a few simple steps to resurrect a system to at least a runnable / good-enough state: