Login package changes MIN_UID in /etc/login.defs -> AccountsService/GDM then ignores existing user (UID 501) -> starts gnome-inital-setup to create user

[Tormod Ravnanger Landet]

On May 8. 2018 I was prompted to upgrade from 17.10 to 18.04.

The upgrade went smooth except that the installer asked me if it could make changes to /etc/login.defs. I thought it was supposed to not ask questions (and stall the upgrade if I was away from the computer), but I pressed yes and it continued. I pressed yes since I had not personally modified this file as far as I can remember and was not particularly attached to its contents.

After reboot gnome-initial-setup wants me to create a new user. There is no (obvious) way to login with my old user, but Ctrl+Alt+F2 luckily worked---I could log in and all my files where still there. I tried changing UID_MIN in /etc/login.defs back to 500 from 1000 (I believe this was the change I was prompted about), but I still could not login graphically, so the /etc/login.defs change may have been unconnected to the bug.

I was able to figure out that the offending program was called gnome-initial-setup and an "apt purge gnome-initial-setup" later I could log in as normal. I do not believe an average user could have figured this out (how many even know about the virtual terminals Ctrl+Alt+FX?).

[Robert Ancell (robert-ancell)]

What has occurred is due to the change of UID_MIN AccountsService has decided that your existing user (501) is now a system user. GDM has then decided that there are no user accounts on the system, so has triggered gnome-initial-setup to create one.

I suspect if you had rebooted after changing UID_MIN back it would have worked fine (user showed in GDM, gnome-initial-setup not run).

I'll assign this to the 'login' package which has decided to change the MIN_UID to 1000 - it may be this is an issue on older systems that used to have this value.

[Jeremy Bícha (jbicha)]

Could you provide more information about this install? When did you originally install Ubuntu? I thought that the minimum UID has been 1000 for several years.

[Tormod Ravnanger Landet (tormod-landet)]

This is my home laptop and I'm at work right now, but it is a 2013 MacBook Air and I'm reasonably confident that I have never reinstalled Ubuntu---just upgraded periodically---so it was originally installed in 2013 or 2014. It is still working great (and things like suspend/resume works much better now than back then).

If it is important I will try to remember to do something like this https://askubuntu.com/a/54317 to figure out the exact version that was first installed. Over all the experience of never having to reinstall has been great and I cannot remember any previous major problems with upgrading between versions.

[Tormod Ravnanger Landet (tormod-landet)]

$ cat /var/log/installer/media-info

Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)