users-admin: create new user with dot/period fails

Thanks for the report. This is indeed a synchronisation issue between users-admin and adduser, the tool which is responsible for actually creating users. I've filed a bug in Debian so they make adduser allow dots in usernames.

Milan, I don't know if the urgency of this issue is low.
Ubuntu installer is affected as well, and I've read on forums about some novice user not being able to perform the installation as of this issue.
Anyway, as I wrote in my bug report, perhaps the dot should be removed because it's used by the chown command: "chown user.group <file>", as an alternative to the colon.

What's the exact behavior of the installer? It doesn't use the same code at all, so that's purely a coincidence it it suffers from the same problem.

Don't worry about the importance, though: I'm currently discussing with an adduser developer, and the fact that I set it to Low doesn't mean it won't be considered. Though if you say the installer is affected, we may want to raise priority - but that will be more important when we know what the fix is, and when backporting will have to be considered.

Personnally, I think chown's behavior regarding the dot is silly, since ':' already serves the same purpose (maybe that's a legacy). Anyway, you can always quote the username if you want, and users-admin will ensure chown correctly interprets a username with a dot in it. So I'd rather fix adduser.

Milan, first of all, as I can see the "adduser" command has a switch "--force-badname" that can be used in this case.
But, if you use this option every kind of strange character will be used. In other words, if you want to use the dot, you need to pass this option only when dot(s) appear in the username, and not for the rest.

Regarding Ubuntu installer, it's not something that happened to me. I just came accross this issue on a usenet newsgroup.
A person was telling that the installation was stuck at the point of creating a user.
After a while he revealed that he was trying to create a user such as "dr.john" (god bless the doctors! :-) )
In other words, you can consider fixing this issue as well, because it's almost the same issue: you need to use --force-badname

Anyway, a man page from BSD says the the dot is there for compatibility with older version of this command: http://www.manpagez.com/man/8/chown/
Perhaps somebody understood that using a dot within a username it was a very common need for the users (in facts, for instance, the dot is very common in the e-mails: name.surname@domain).
In other words I changed my idea and you're right: you can fix the tool and allow *only* dots.... otherwise, do it the other way: allow only "_" and "-"
It's your choice :-)

Of course, we can pass --force-badname, but if we consider dots as acceptable, adduser should accept them by default.

About chown, there's absolutely no need to change the tool, as long as people that add dots to their usernames and use chown from the commandline know what they are doing. Anyway, if they don't, they'll get an error message, and they'll understand the issue - newbies don't use chown.

I already fixed the installer problem in ubiquity 2.5.0 in natty - see bug 555896.