Case-sensitivity of account usernames

Question

When installing Ubuntu, we're restricted to lower-case usernames. But recently I registered for a shell based on Ubuntu and logging in is done by the username registered to sign in to that site. The username starts with upper-case letter, and when logging using SSH, I need the letter in uppercase to log in - it refuses me if I use lowercase.

What's the deal? I want to use uppercase letters on the account of my regular install if possible.

Answer 1

The reason why isn't clear - though it appears that some programs don't distinguish between CAPITAL and lowercase usernames. As such there lies a potential for conflict if you have a Marco and a marco account.

There currently doesn't appear to be any way to have this done via the users-admin or Ubiquity - likely that these rules are hard-coded instead of pulled from the adduser.conf file.

You add the user via the command-line if you force a "bad username":

root@mine:~# adduser --force-badname Marco
Allowing use of questionable username.
Adding user `Marco' ...
Adding new group `Marco' (1002) ...
Adding new user `Marco' (1002) with group `Marco' ...
Creating home directory `/home/Marco' ...
Copying files from `/etc/skel' ...
Enter new UNIX password: 
Retype new UNIX password: 
passwd: password updated successfully
Changing the user information for Marco
Enter the new value, or press ENTER for the default
        Full Name []: Marco Ceppi
        Room Number []: 
        Work Phone []: 
        Home Phone []: 
        Other []: 
Is the information correct? [Y/n] y

If you want to add users without needing to --force-badname you can change this line in /etc/adduser.conf:

#NAME_REGEX="^[a-z][-a-z0-9_]*\$"

To this

NAME_REGEX="^[a-zA-Z][-a-zA-Z0-9_]*\$"

This will allow Uppercase names for users. While there is no way to add users to additional groups via the adduser command you can use the usermod command instead:

usermod -G admin Marco