Re: cp --preserve=mode and NFS4 ACLs

[Pádraig Brady]

On 24/09/2024 20:09, Ross Burton wrote:
> So the greater context of this is that I'm trying to copy a file from
> a NFS server, preserving mode and timestamp. The current script does
> `cp -a` which as discussed here breaks when it tries to preserve the
> mode.  Looking at our use case, the only things we actually care about
> is the timestamp and user executable bit.  In my testing the u+x bit
> is always preserved and --preserve=mode mainly impacts whether the
> umask is respected or not.  Am I missing any fine details or is
> --preserve=timestamps sufficient for our needs?

The full online documentation is informative on all these points:
https://www.gnu.org/software/coreutils/cp

"
--preserve=mode
  Preserve attributes relevant to access permissions, including
  file mode bits and (if possible) access control lists (ACLs).
  ACL preservation is system-dependent, and ACLs are not
  necessarily translated when the source and destination are on
  file systems with different ACL formats (e.g., NFSv4 versus
  POSIX formats).

...

  In the absence of this option, the permissions of existing
  destination files are unchanged.  Each new file is created with the
  mode of the corresponding source file minus the set-user-ID,
  set-group-ID, and sticky bits as the create mode; the operating
  system then applies either the umask or a default ACL, possibly
  resulting in a more restrictive file mode.
"

cheers,
Pádraig