chmod g+ws unsuccessful, "NULL SID" icacls missing
Wed Feb 8 21:05:50 GMT 2023
I briefly raised this issue months ago and am trying to resolve it again
What I am trying to do is setup permissions so multiple users on one
machine can share full control over a particular directory hierarchy.
On Linux I have usually been able to make things work with:
$ mkdir shared_dir
$ chgrp shared_group shared_dir
$ chmod g+ws shared_dir
$ umask 2
User shells are configured with umask 2 so files they create have group
write. Users belong to shared_group. Files and subdirs created under
shared_dir are all in group shared_group. Files moved in retain their
original group, but the group members still have permission to rename or
$ chmod g+ws fails to set the 's' bit, and the resulting icacls output
does not contain any "NULL SID" entries. I am seeing the same problem on
(at least) two different systems setup by my organization. One of these
was just re-imaged and I installed Cygwin yesterday with no customized
configurations. AV is Windows Defender, but I suspect if that were the
culprit, there would have been more noise.
I suspect there might be a group policy or something that is interfering
with Cygwin's strategy for implementing POSIX permissions. I am pretty
sure this worked correctly at some point in the past.
Has anyone encountered this?
Does group policy seem like a likely suspect? Anyone know which
policy(ies)? I think I might be able to get IT to cut me slack if I knew
what to ask for.
I have also played with using setfacl directly to add permissions, but
as anyone who has read about Cygwin file permissions might guess, that
tends to have mixed/poor results, but I'd be open to any suggestions.
More information about the Cygwin