pure number allowed as username in the useradd command?

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On 12/02/2010 07:42 PM, Marko Vojinovic wrote:
> On Thursday 02 December 2010 21:02:17 Aaron Konstam wrote:
>> On Thu, 2010-12-02 at 18:10 +0100, Joachim Backes wrote:
>>> Can somebody explain why pure numbers are allowed for username in the
>>> useradd command?
>>>
>>> sudo useradd 123456789
>>>
>>> is not rejected!
>>>
>>> As is known, this leads to big problems if referring to such a user and
>>> the username differs from the userid: should such a username be
>>> interpreted as username or userid?
> 

   Can you be specific - what big problems are these ? Never tried, but
it is by means obvious that this would be problematic.

> So I guess 12345 should be a valid username as any other, and useradd 
> correctly allows for creation of such usernames. No bug there.
> 

 Agreed - without knowing what the problems are it is hard to say that
useradd (or anything else) should disallow numerical id's ..