login impossible after the modification of the group for the folder /etc

Question

Due to some permission purposes I have changed the group of all folders in /etc. Now I can't log in any more. Is there a way to go back. (I'm using ubuntu 20.04 on a VM)

Many thanks in advance.

Answer 1

Possible options:

• Restore a backup if you have one.
• Restore a VM snapshot if you have one.
• Boot the VM from an ISO image with a live system to
  • repair your system, if you know what exactly to change (see pLumo's answer), or
  • save your important data, e.g. to a shared folder. Then install a fresh system and restore your saved data.
• Create a new VM with a fresh install, add the virtual harddisk of your old VM to the new VM and
  • copy your important data directly from the old disk to the new disk or
  • compare the directories between the old disk and the new disk fix the broken ones on the old disk.

Answer 2

You can quite easily rollback, as most directories have group root. Only a few directories are different and that should be the same or similar between systems.

Run following commands from a terminal:

# change group for all directories to root
sudo find /etc -type d chgrp root {} +

# change group of some other directories to their default groups
sudo chgrp dip /etc/chatscripts
sudo chgrp dip /etc/ppp
sudo chgrp dip /etc/ppp/peers
sudo chgrp ssl-cert /etc/ssl/private
sudo chgrp lp /etc/cups
sudo chgrp lp /etc/cups/ssl
sudo chgrp lp /etc/cups/ppd

This list is copied from my system, got it with command

sudo find /etc -type d -not -group root -printf 'sudo chgrp %g %p\n'

Your setup might differ slightly, e.g. on another machine I also have /etc/postgresql and subdirs belong to group postgres. Anyways, this should make you be able to login again.

If you cannot access a terminal on the machine, you need to run from a live system, mount your drive and change /etc/ to /path/to/mountpoint/etc/ for the commands above.