Unable to log in via GUI if you change GID and UID

Question

I have created an additional user via the GUI and subsequently changed their GUI and UID so they match other servers I have on the network (and I can use shared filesystems properly). Once I do that the user is not available on the login window, user admin window, or as an available user in the Power menu on the GUI top right.

Question: Can anyone suggest how to change GUI and UID for users in Elementary after they are created?

Note: I did find a workaround - and that is to create the user via the command line from an admin account using useradd below. But if you change it after creating via the GUI then it breaks things.

sudo useradd -u 502 -g 20 username

Ubuntu and Fedora let you specify the UID/GID in the GUI when creating the user - so that could be a nice feature request for ElementaryOS

Thanks

Answer 1

My workaround above stopped working after a reboot. I think I found the issue...

/etc/adduser.conf defines the ranges:

FIRST_SYSTEM_UID=100
LAST_SYSTEM_UID=999

FIRST_SYSTEM_GID=100
LAST_SYSTEM_GID=999

# FIRST_[GU]ID to LAST_[GU]ID inclusive is the range of UIDs of dynamically
# allocated user accounts/groups.
FIRST_UID=1000
LAST_UID=59999

FIRST_GID=1000
LAST_GID=59999

It looks like the UI ignores UIDs/GUIs that are outside the non-system range.

It is only a problem for me because I am trying to match UID and GID with macOS (which uses the 500 range for users and 20 for "staff" group.