bug#20884: copying NFS4 ACLs portably

[Michael Stone]

On Tue, Jun 23, 2015 at 08:22:44PM +0200, Andreas Grünbacher wrote:
> Somewhat. The "system.nfs4_acl" attribute is nfs specific though: its
> format isn't
> well suited for other file systems. Adding support to gnulib would only make
> copying permissions on nfs work, not across different file system types.

Well, moving things around on an NFSv4 filesystem is the request I 
received, not converting the ACL from NFSv4 to POSIX. :) I'm not 
convinced that it's possible to transparently map arbitrary ACLs from 
one filesystem to another given different semantics, so I'm not sure 
that's a goal worth holding up the ability to copy NFS4 ACLs 
indefinitely. Other implementations just warn when they can't preserve 
ACLs, which seems reasonable.

The current situation seems pretty bad, in that something is happening 
that seems to be almost-working, but which shouldn't be working at all. 
It's double bad that the behavior of coreutils depends on a config file 
(/etc/xattr.conf) which almost no distributions include by default. And 
if we start to include it, then something that people are currently 
using to copy NFS4 ACLs stops working (without any changes in 
coreutils).

Mike Stone