Different commands give different groups

Different commands give different groups

[gsingh93]

Why do these two commands give different groups? It's the same user.

Gulshan@GSJK-PC /etc
$ id Gulshan
uid=1000(Gulshan) gid=545(Users) groups=545(Users),0(root)

Gulshan@GSJK-PC /etc
$ id
uid=1000(Gulshan) gid=545(Users) groups=545(Users),513(None)

Furthermore, the commands mkgroup and mkpasswd give the orginial states of
their corresponding files instead of what I changed them to. Why is that?
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Re: Different commands give different groups

[Eric Blake]

On 09/30/2011 09:49 PM, gsingh93 wrote:
>
> Why do these two commands give different groups? It's the same user.

Because the effective gid set for the existing process differs from the 
recorded groups in /etc/groups - most likely, you've changed /etc/groups 
but haven't logged out and back in to start a new process hierarchy that 
uses the new groups.

>
> Gulshan@GSJK-PC /etc
> $ id Gulshan
> uid=1000(Gulshan) gid=545(Users) groups=545(Users),0(root)

That's what the groups will be if a new process is started for Gulshan.

>
> Gulshan@GSJK-PC /etc
> $ id
> uid=1000(Gulshan) gid=545(Users) groups=545(Users),513(None)

Whereas that's what the groups are now for the current process.

This aspect of your situation is not cygwin-specific, the same behavior 
can be observed in other OSs when you change the user database after a 
particular user already has a process started.

>
> Furthermore, the commands mkgroup and mkpasswd give the orginial states of
> their corresponding files instead of what I changed them to. Why is that?

This part is cygwin-specific - and the answer is that mkgroup and 
mkpasswd are querying Window's database of user information, not /etc 
(so that you can then populate /etc with information that matches the 
Window's database).  Windows doesn't care what you put in /etc, so the 
amount of changes you can make in those files that still have a 
worthwhile visible effect to cygwin processes is a bit limited.

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Eric Blake   eblake@redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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Re: Different commands give different groups

[gsingh93]

That makes sense, but I've completely restarted my computer and yet it still
shows the old groups. So a new process that uses the new groups hasn't
started. Any idea why?

eblake wrote:
> 
> On 09/30/2011 09:49 PM, gsingh93 wrote:
>>
>> Why do these two commands give different groups? It's the same user.
> 
> Because the effective gid set for the existing process differs from the 
> recorded groups in /etc/groups - most likely, you've changed /etc/groups 
> but haven't logged out and back in to start a new process hierarchy that 
> uses the new groups.
> 
>>
>> Gulshan@GSJK-PC /etc
>> $ id Gulshan
>> uid=1000(Gulshan) gid=545(Users) groups=545(Users),0(root)
> 
> That's what the groups will be if a new process is started for Gulshan.
> 
>>
>> Gulshan@GSJK-PC /etc
>> $ id
>> uid=1000(Gulshan) gid=545(Users) groups=545(Users),513(None)
> 
> Whereas that's what the groups are now for the current process.
> 
> This aspect of your situation is not cygwin-specific, the same behavior 
> can be observed in other OSs when you change the user database after a 
> particular user already has a process started.
> 
>>
>> Furthermore, the commands mkgroup and mkpasswd give the orginial states
>> of
>> their corresponding files instead of what I changed them to. Why is that?
> 
> This part is cygwin-specific - and the answer is that mkgroup and 
> mkpasswd are querying Window's database of user information, not /etc 
> (so that you can then populate /etc with information that matches the 
> Window's database).  Windows doesn't care what you put in /etc, so the 
> amount of changes you can make in those files that still have a 
> worthwhile visible effect to cygwin processes is a bit limited.
> 
> -- 
> Eric Blake   eblake@redhat.com    +1-801-349-2682
> Libvirt virtualization library http://libvirt.org
> 
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> 
> 
> 

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