I was messing around with permissions and ownership in Ubuntu without knowing much of the consequences, one thing that leaded to not being able to login with my username/password (login screen loop as some may call) was when I changed ownership of the root “/” to the logged in user “mahmoud”.

To fix that:

1. login in Recover Mode
   1. restart
   2. press and hold “Shift”
   3. from GRUB, select Advanced settings
   4. select latest kernel with (recovery mode) post-fixed
   5. select “root”
2. since filesystem is in read-only mode, we need to remount it in read-write:
   sudo mount -o remount,rw /
3. Now we can return ownership back to root by:
   sudo chown root:root /
4. to make sure we’re good, ls -lah, everything should have root
5. enter reboot and we’re good to go