pure number allowed as username in the useradd command?

[Joachim Backes]

On 12/03/2010 02:04 AM, Genes MailLists wrote:
> 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.

See chown: allows username and userid as new owner. So if a numerical
userid is the same as a username (having another userid), which user is
meant? The user with this username, or the user with this userid?

> 
>> 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 ..


-- 
Joachim Backes <joachim.backes at rhrk.uni-kl.de>

http://www.rhrk.uni-kl.de/~backes

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