How (not) to kill Ubuntu and how to revive Ubuntu

My killing Ubuntu is a silly story of sudocide.  Prior to departing to faraway in October 2009 I decided to backup my system on a new USB disk.  I hadn't liked the FAT32 format (even though it was developed by Bill Gates himself) needed for my MacBook Pro, for clipping large files and for spoiling file attributes and so not permitting rsync.  So I google-found that sudo mkfs /dev/sdb1 formats the preferable ext3.  But then the disk ownership became root:root.  I tried to correct that with sudo chown -R myusername:myusername but that did not operate in the disk directory that (I thought) I was in but on my system disk.  I killed it fast but it had done damage, at least to files in /root.  In a repair trial I typed sudo chown -R root:root /root/.* where I added the period because the files and directories in @/root are .XXX-hidden.  This was a bigger mistake:  the wildcard .* apparently implies also ..* so the operand does not only go down the tree but also back up, into the system top and then down that.  This is perhaps logical but was quite unexpected by me.  And so all files on the disk became root:root, also all mine, and sudo would no longer work ("must be setuid root") so that I could not reclaim ownership of my own directories and files.  Upshot: I had sudocided my usage.

Reviving my Ubuntu usership became a long story.  Help came via email via my discarded MacBookPro from a Utrecht University system manager (the best I ever met) and the former graduate student mentioned above (not to be replaced by Google after all).  Power on and press ESC fast before the grub loader starts, or SHIFT all the time in case yours is a single-system setup.  Select and boot the recovery-mode version (probably the second entry).  Cursor down to get the root command line prompt (without net access).  Now you are root (superuser).  Type:

  chown -R myusername:myusername /home/myusername
  chown root:root /usr/bin/sudo
  chmod 111 /usr/bin/sudo
  chmod +s /usr/bin/sudo
and then restart.  That helped a lot, but many system files still had ownership root:root instead of something else.  So I followed this advice to try complete package reinstallation:
  sudo su -  
  dpkg --get-selections | egrep -v deinstall | awk '{print $1}' | 
    egrep -v '(dpkg|apt|mysql|mythtv)' | xargs aptitude -y reinstall
but that stopped after the deinstall for lack of connectivity, perhaps loss of proxy settings in the process.  Much more didn't work then.  The eventual remedy, after returning home, was to update from Ubuntu 9.04 to Ubuntu 9.10 which had then become available, letting it reinstall all packages properly.