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Distribution: Fedora 18, Slackware64 13.37, Windows 7/8
User name with a period
All the users on my home network use the convention [<givenName>.<surName>]; e.g. Bill.Baxter, Jill.Bonniville, etc
For whatever reason slackware rejects these names as illegal. I have been using this convention for over a decade and I've never seen this with any other version of Linux.
I know I can manually hack at the /etc/passwd file and then shadow the pass and all that but I really don't want to do that. Are these rules defined in a script I could modify and is there any intrinsic reason for this constraint (in other words will having ids like this damage the system in any way)?
I've got a mixture of Windows 2003/2008 and Linux servers along with an even mix of Windows XP/7 and Linux workstations and changing all our usernames on the servers is not really feasible.
useradd rejects usernames with periods, unless your distribution happens to be using a patched version of useradd. I know Fedora accepts periods in usernames, and I would guess the same goes for RHEL and CentOS.
Having usernames with periods may break some scripts or tools, as the period is occasionally used as a separator. For instance, how should this command be interpreted: chown john.doe <filename>. Are you changing the owner to "john.doe", or "john" and the group "doe"?
Through a Google search, I stumbled upon a presentation which discusses this and related issues.
The reason being that they would have been invalid on a traditional UNIX system. Pity the convention in microsoft land wasn't to use an underscore as that would have worked on both platforms, but then as the choice of '\' v '/' path separator in DOS shows, they just had to be different for the sake of it.
Actually, the correct usage pattern for chown is "chown user:group item".
That is the correct usage today, but "." is still accepted as a separator to retain legacy compatibility.
I believe the latest Unix standards document covering Unix/POSIX username convensions (IEEE Std 1003.1, 2004 Edition) allows periods, but until all legacy compatibility has been removed from tools and applications, having periods in usernames is likely to cause breakage.