[CentOS] Why are dots in username & groupname no longer allowed?

[Rodrigo Barbosa]

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On Fri, Dec 30, 2005 at 12:48:18PM +0100, Remco Barendse wrote:
> For some strange reason I am no longer able to create groupnames or 
> usernames (with useradd and groupadd) that contain a dot.
> 
> Uptill now it was possible to create user&groupnames like c.smith but now 
> I get these errors:
> 
> [root at server etc]# useradd c.smith
> useradd: invalid user name 'c.smith'
> 
> [root at server1 etc]# groupadd c.smith
> groupadd: c.smith is a not a valid group name
> 
> Anything without a dot works without problems.
> 
> The box is a (fully updated) CentOS 3.6 x86_64 box with Dual Opteron cpu.

As far as I know, dots where never supposed to be valid characters for
Unix usernames. The historical reasons are many, including the syntax
of some commands that take username as a parameter. Several commands will
that username.group as a parameter and, as you can see, the dot can
get in the way of that.

So, if you ask me, the upstream provider just corrected a long standing
compatibility issue.

In any case, if you really want to have usernames with dots on it,
you can create them manualy, or create them without the dot, and then
change them by editing the apropriate files.

Best Regards,

- -- 
Rodrigo Barbosa <rodrigob at suespammers.org>
"Quid quid Latine dictum sit, altum viditur"
"Be excellent to each other ..." - Bill & Ted (Wyld Stallyns)

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