"Failed to create user" due to regular expression error

I'm running Ubuntu 12.10 desktop 32 bit. Currently I have only a user, type administrator. I'd like to create another administrator user but I keep getting the following error:

Failed to create user

GDBus.Error:org.freedesktop.Accounts.Error.Failed: running '/usr/sbin/adduser' failed: /usr/sbin/adduser returned an error (1): adduser: Please enter a username matching the regular expression configured via the NAME_REGEX[_SYSTEM] configuration variable. Use the `--force-badname' option to relax this check or reconfigure NAME_REGEX.

Any suggestion is appreciated.

The username you're entering contains bad characters. Try entering a simple username containing only lower-case English letters - daniel is good, &&Daniel <*> Johnson## is not so good.

You normally get this message if you are trying to create a user with a name that contains characters that are considered to be un acceptable as per your NAME_REGEX file. You can try again changing the username with the GUI or you can relax the check by using the command line with the following command.

sudo adduser --force-badname <username>

and then if you want to add the user to the sudo group run the following command.

sudo adduser <username> sudo

In Debian systems, the regex defining acceptable user names is found in /etc/adduser.conf.

A typical regex (found on my system) is:

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

I don't want to veer too far off topic with regex parsing, but the caret ^ symbol indicates the beginning character of the user name must be between lowercase a and lowercase z. The remaining characters may be lowercase a-z, 0-9, hyphen, or underscore. As mentioned in other answers, you can override this check if you like. By default, regexes are case-sensitive.

I faced the same problem -and I solved it- when I wrote

# adduser --home /Ali Ali

I got the error of

adduser --home /Ali Ali
adduser: Please enter a username matching the regular expression configured
via the NAME_REGEX configuration variable.  Use the `--force-badname'
option to relax this check or reconfigure NAME_REGEX.

I solved it just by removing the uppercase letters as shown below

# adduser --home /ali ali
Adding user `ali' ...
Adding new group `ali' (1001) ...
Adding new user `ali' (1001) with group `ali' ...
Creating home directory `/ali' ...
Copying files from `/etc/skel' ...
passwd:     
passwd: password updated successfully