HOWTO: Change your default user account to a system account

When you deploy a new Ubuntu installation, the first user it creates (uid=1000) will be given sudo privileges.

Sometimes it is desirable to have a specific "admin" user on your system that is separate from your normal user accounts which are located in the uid=1000+ range.

For example, if you are setting up an LDAP network.

Unfortunately, you can't set the uid manually during the initial installation process but you can change it afterwards.

Note:

If you make a mistake during this procedure it is possible to lock yourself out of the system completely. This is not such an issue if this is a freshly installed system but if it is already up and running in some sort of role, then you need to be extra careful. You have been warned!

I am working here with a fresh Lucid server install, and my uid=1000 user is called "sysadmin".

Login to a console session as root;

~$ sudo -i

Manually edit your passwd file;

~# vi /etc/passwd

At the end of the file will be the entry for the "sysadmin" account;

sysadmin:x:1000:1000:system admin,,,:/home/sysadmin:/bin/bash

Change the two "1000"'s to "999";

sysadmin:x:999:999:system admin,,,:/home/sysadmin:/bin/bash

Make the same change in the "group" file;

vi /etc/group

Change the "sysadmin" line to;

sysadmin:x:999:

Changing the uid of a user will break the permissions in their home directory;

~# ls -al /home/sysadmin
total 32
drwxr-xr-x 3 1000     1000     4096 2011-06-23 13:34 .
drwxr-xr-x 3 1000     1000     4096 2011-06-23 13:32 ..
-rw------- 1 1000     1000       48 2011-06-23 13:34 .bash_history
-rw-r--r-- 1 1000     1000      220 2011-06-23 13:32 .bash_logout
-rw-r--r-- 1 1000     1000     3103 2011-06-23 13:32 .bashrc
drwx------ 2 1000     1000     4096 2011-06-23 13:33 .cache
-rw-r--r-- 1 1000     1000      675 2011-06-23 13:32 .profile
-rw-r--r-- 1 1000     1000        0 2011-06-23 13:33 .sudo_as_admin_successful
-rw------- 1 1000     1000      663 2011-06-23 13:34 .viminfo

You can fix that by issuing the following commands;

~# chown sysadmin:sysadmin /home/sysadmin
~# chown sysadmin:sysadmin /home/sysadmin/.*

When we setup LDAP later we will want to mount /home to an NFS share. Unfortunately, when we do this we will overwrite our sysadmin's home folder! Let's move it to the root ("/") directory.

~# mv /home/sysadmin /

We will need to change the path in the passwd file;

~# vi /etc/passwd

Change it from;

sysadmin:x:999:999:sysadmin,,,:/home/sysadmin:/bin/bash

to this;

sysadmin:x:999:999:sysadmin,,,:/sysadmin:/bin/bash

Check that all is well;

~# ls -al /sysadmin
total 32
drwxr-xr-x 3  sysadmin sysadmin 4096 2011-06-23 13:34 .
drwxr-xr-x 23 root     root     4096 2011-06-24 11:29 ..
-rw------- 1  sysadmin sysadmin   48 2011-06-23 13:34 .bash_history
-rw-r--r-- 1  sysadmin sysadmin  220 2011-06-23 13:32 .bash_logout
-rw-r--r-- 1  sysadmin sysadmin 3103 2011-06-23 13:32 .bashrc
drwx------ 2  sysadmin sysadmin 4096 2011-06-23 13:33 .cache
-rw-r--r-- 1  sysadmin sysadmin  675 2011-06-23 13:32 .profile
-rw-r--r-- 1  sysadmin sysadmin    0 2011-06-23 13:33 .sudo_as_admin_successful
-rw------- 1  sysadmin sysadmin  663 2011-06-23 13:34 .viminfo

On another console, confirm that you can login as the sysadmin user.

You should get a proper bash prompt;

sysadmin@galileo:~$

Note:

If your system has a GUI login, be aware that the logon screen will not display usernames for users with a UID of less than 1000. To login using the "sysadmin" account in such a case, you would need to type the name in to the username field manually.