[nmglug] Group file altered

[Tom Rushton]

I'm a complete novice and have been playing with the latest Ubuntu 
distro for a few weeks and somehow managed to overwrite  the  /etc/group 
and  group-  files, eliminating all groups except root and nogroup.  It 
appears that both files were overwitten at the same time. Don't ask me 
how I did it--I haven't a clue.  I managed to get rebooted by adding 
back the groups identified in the passwd file with the proper group 
number, then adding back the rest of the groups that popped up in the 
error messages on reboot, but I haven't been able to regain full 
functionality, perhaps because I didn't guess right on some of the group 
numbers for the groups not identified in the passwd file or because I 
didn't reassign users to all of the necessary groups.  So before doing a 
complete reinstall, and in case I do it again, I thought I'd ask if 
anyone knows of a way to recover from this (probably should have asked 
earlier, but I've learned a lot going through this exercise in any event).
~Tom Rushton