SetUID and SetGID question

Ioannis Vranos ioannis.vranos at
Sat Sep 10 17:05:05 UTC 2011

On Sat, Sep 10, 2011 at 7:46 PM, Smoot Carl-Mitchell <smoot at> wrote:
> setuid sets the userid to the owner of the executable.  setgid sets the
> primary group id to that of the executable file.  With either flag you
> are changing the allowed authorization from the user executing the
> program to another user or group or both.
> setgid program are less common, but might be used where you do not want
> the program to run with root privileges, but do want it to have access
> to files which are "owned" by the group.
> sendmail for example runs setgid in the smmsp group which allows the
> executable to create files in the client mail queue without allowing
> more permissive access.

Hi Smoot,

Thank you for your answer. When enabling both SetUID and SetGID for an
executable, hasn't it the same effect as enabling SetUID only?

This is where I am confused. If the answer is yes, wouldn't it be
better to not be allowed enabling both, for ambiguity reasons?


Ioannis Vranos

More information about the ubuntu-users mailing list