How to change the order of users in gdm login screen?

I'm the only frequent user on a system using gdm, but in the login screens' user list I am not moved upwards (due to most frequent use), and I cannot find a possibility to order the users manually. I confirmed they are not ordered by numeric UID. The same question has been answered here (and here another related one), but for older systems using consolekit, which has been replaced by systemd-logind and AccountsService in the meantime.

The last command lists the past successful logins on the system. This information is stored in the /var/log/wtmp file, and is used by gdm since version 3.17.2 to sort the list of users.

If you delete the /var/log/wtmp file and then reboot, the list of users will default to alphabetical order. After your next login, your user will become the most frequently used so that it will appear on the top of the list.

Note: You will lose the login history of the system if you delete the /var/log/wtmp file. You may want to create a backup of that file.

Tested in Ubuntu Desktop 20.04.3 and 21.04

Building on Alejandro's answer, if you do not want to delete the /var/log/wtmp file, you can run a script that will "stack the deck" to ensure a specific sort order through the use of the login and expect commands.

Here's how you can do it:

0. Open Terminal (if it's not already open)

1. (If Required) Install expect:

   sudo apt install expect
   

2. Switch to the super-user and head to /root for the sake of cleanliness:

   sudo su 
   cd ~
   

3. Create a script that will login as a given account. For this example, let's call it logins.sh (but you can call it whatever you'd like):

   vi logins.sh
   

   ^{Note: Feel free to use any text editor. The use of vi in this example is more the result of muscle memory than an explicit recommendation.}

4. Paste this into the new file:

   #!/usr/bin/expect
   
   set timeout 10
   
   set user [lindex $argv 0]
   
   set password [lindex $argv 1]
   
   spawn login $user
   
   expect "Password:"
   
   send "$password\r"
   
   expect "$user@{hostname}:~$"
   
   send "exit\r"
   
   interact
   

   ^{Note: Be sure to replace {hostname} with the host of your computer.}

   Save the file and exit.

5. Set the file as executable:

   chmod +x logins.sh
   

6. Test it:

   ./logins.sh nozomi superSecretPassword\!123
   

   ^{Note: Unless you share a name with my dog, be sure to change nozomi with the proper account name and superSecretPassword\!123 with the proper password. If your password contains characters that may be misunderstood by bash such as !, be sure to escape them with a \.}

   If everything works, you will see that the specified account is logged into and, after about 8~10 seconds, it is automagically logged out.

7. Verify this added a record to /var/log/wtmp:

   last
   

   You should see something like this:

   $ last
   nozomi   pts/1                         Thu Sep  9 00:38 - 00:39  (00:00)
   

8. Run the script dozens, hundreds, or thousands of times:

   for i in {1 .. 999}; do /root/logins.sh nozomi superSecretPassword\!123; done
   

   ^{Note: Be sure to replace 999 with the number of times you'd like the script to run. Be aware that the number should be greater than zero and that each run will require about 10 seconds in total to complete. Also be sure to replace the username and password with the account you want to have set at the top.}

9. If there are other accounts that you would like near the top, but not at the top, run the command in #8 again, with fewer runs in the for loop. Be aware that at roughly 6 runs per minute, 1000 runs will require about 2h45m in human time to complete. You may want to run this overnight.

10. (Optional) Consider modifying the script to run for multiple accounts and scheduling it to run daily or weekly.

This has been tested on stock Ubuntu 20.04 LTS and 21.04, but should work with every version of Ubuntu from (at least) 18.04 upwards.

The reason might be, that your gdm might be configured not to include all users.

This behaviour used to be configured in /etc/gdm3/custom.conf in the [greeter] section (Include=) - this however does not seem to work anymore (see gdm disregards /etc/gdm/custom.conf exclude user list).

It might be that either user azrdev is considered a system-account by GDM3 and therefore not displayed in the user-list at all OR system-accounts are incorrectly classified as non-system accounts and therefore ending at the top of the list.

If that is the case, you can add a file named /var/lib/AccountsService/users/username and change the value of

[User]
SystemAccount=true

to remove that user from the GDM greeter.