Ok, I've done some reading on this topic. osx ACLs are much more like windows than posix. You can read about them here: http://www.bresink.com/osx/193281/Docs-en/ACL.html It seems that suse and unitedlinux have defined a mapping between windows and posix acls for samba: http://www.suse.de/~agruen/acl/linux-acls/online/ I suppose one could do the same mapping for osx rsync. However, this will lose information when using rsync to backup a mac (all the special rights). What does rsync do when saving ACLs from windows?