DESCRIPTION

     setfsgid sets the group ID that the  Linux  kernel  uses  to
     check  for  all  accesses  to the file system. Normally, the
     value of fsgid will shadow the value of the effective  group
     ID.  In  fact,  whenever  the effective group ID is changed,
     fsgid will also be changed to new value of  effective  group
     ID.

     An explicit call to setfsgid is usually only  used  by  pro-
     grams  such as the Linux NFS server that need to change what
     group ID is used for file  access  without  a  corresponding
     change  in the real and effective group IDs. A change in the
     normal group IDs for a program such as the NFS server  is  a
     security  hole  that  can expose it to unwanted signals from
     other group IDs.

     setfsgid will only succeed if the caller is the superuser or
     if  fsgid  matches either the real group ID, effective group
     ID, saved group ID, or the current value of fsgid.

RETURN VALUE

     On success, the previous value of  fsgid  is  returned.   On
     error, the current value of fsgid is returned.

CONFORMING TO

     setfsgid is Linux specific and should not be  used  in  pro-
     grams intended to be portable.

BUGS

     No error messages of any kind are returned to the caller. At
     the  very  least,  EPERM  should  be  returned when the call
     fails.

SEE ALSO

     setfsuid(2)