From: Daniel Berger <djberg96@...>
Date: 2009-01-28T23:01:23+09:00
Subject: Re: Super User Can't Change UID?

James Gray wrote:
> On Jan 27, 2009, at 5:11 PM, James Gray wrote:
> 
>> Why would the super user not be able to switch UID's?
>>
>>  $ sudo ruby -r etc -e 'Process.uid = Etc.getpwnam("james").uid'
>>  Password:
>>  -e:1:in `uid=': Operation not permitted (Errno::EPERM)
>>      from -e:1
> 
> Another data point on this odd issue:  Apple's bundled Ruby (I'm on OS 
> X) works:
> 
>   $ sudo /usr/bin/ruby -r etc -e 'Process.uid = Etc.getpwnam("james").uid'
>   Password:
>   $
> 
> It's just the Ruby I built that fails.  How could I have messed this up 
> in the build?

Are you on 10.4.x?

If I had to guess, I'd bet Apple replaced setreuid() with seteuid(), but 
that's a guess.

I've never really understood the way OS X manages users. My own account 
is not in /etc/passwd, but shows up in NetInfo.

Regards,

Dan