I just installed Ubuntu 12.04 AMD64 on a new (empty) hard disk (because the previous crashed)

Since I am quite familiar with Debian, I created two accounts with the adduser command.

Since I am also having an NFSv3 file system, I explictly gave user ids when creating them (for simplicity, I keep the same user id on the home server, running Debian; the user names contain digits; I'm not using LDAP), e.g.

  # grep bethy /etc/passwd
  bethy46:x:501:501:Bethy XXX,,,06123456:/home/bethy:/bin/bash
  # grep bethy /etc/group
  bethy64:x:501:
  # grep bethy /etc/shadow
  bethy46:$6$vQ-wmuchmorethings-2o/:15479:0:99999:7::

Of course /home/bethy exists

^{The actual user name is slightly different, and I am not showing the real entries (for obvious privacy reasons)}

However, these users don't appear at graphical login prompt (lightdm).

And they exist in the system, they have entries in /etc/passwd & /etc/shadow and I (partly) restored their /home

I've got no specific user config under /etc/lightdm ; file /etc/lightdm/users.conf mentions

 # NOTE: If you have AccountsService installed on your system, then LightDM
 # will use this instead and these settings will be ignored

but I have no idea of how to deal with AccountsService thru the command line

^{As you probably guessed, I really dislike doing administrative tasks thru a graphical interface; I much prefer the command line}

What did I do wrong? How can a user entry not appear in lightdm graphical login? (I need to have my wife's user entry apparent for graphical login).

^{I am not asking how to hide a user, but how to show it in lightdm graphical prompt}

work-around

As I have been told in comments by Nirmik and by Enzotib, lightdm probably don't show any users of uid less than 1024. So I changed all the uid to be more than 8200 (including on the Debian NFS server) and this made all the users visible at the graphical prompt.

It is a pain that such a threshold is not really documented.