Comment 13 for bug 23475

I think installer should limit the username to [a-z][a-z0-9]{0,7}, like "tkarvine".

This fixes most username related problems. Often users ask why this is not enforced automatically by the installer. Users normally come up with an obvious way to choose an ascii username: "Maija Mäkinen" -> "mmakine", "Heikki Håkan" -> "hhakan". This process can also be automated. Users full name can be stored in "Full Name" field in /etc/password.

The case for 8 char ascii usernames:
- They work: users are able to log in graphically. No point pretending Ubuntu supports unicode usernames if it does not support them.
- Many services use usernames and assume they are ascii. For example, email addresses must in practice be ascii.
- File sharing is much easier, for example with Samba or with sshfs to another brand of Linux.
- Can be typed trough remote connections, such as ssh, even when non-ascii characters are not transferred correctly.
- Because many problems related to non-ascii usernames are not in control of Ubuntu, non-ascii usernames can not work reliable in near future.

I suggest that installer should start enforcing lower case 8-char ascii usernames that start with a letter: [a-z][a-z0-9]{0,7}.