Using pre2 for backing up a mac
Wesley W. Terpstra
terpstra at dvs1.informatik.tu-darmstadt.de
Sat Oct 13 14:07:07 GMT 2007
With the new ACL+xattr support and fake super (I'm glad this made it
in!), it seems like my dream of being able to use rsync --link-dest
to backup my mac is almost within reach!
If you take a look at
you can get an overview of the meta-data which needs to be saved for
faithful backups on a mac.
rsync 3pre2 now handles all but three items:
1. bsd flags
2. "locked flag" (supposedly finder meta-data)
3. creation date
There is a (broken) patch in the pre2 directory for backing up bsd
flags. I gather these don't exist on linux? On a mac (and I assume
BSD in general) you can get them from st_flags in struct stat and set
them with chflags(2). If linux doesn't support them, it might be
possible to copy the flags into an xattr.
The "locked flag" is actually just the bsd immutable flag; the author
of that article is wrong. So solving the bsd flag issue solves this.
The creation date is AFAIK a mac os specific piece of meta-data and
can be accessed via the set/getattrlist + ATTR_CMN_CRTIME system call
on a mac. Again, this meta-data might be reasonably converted into an
I've noticed the ACLs on a mac are only saved in an xattr on a linux
machine when the fake-super option is used. I'm not sure if this is
the right thing to do, and I'm not sure whether the bsd flags /
creation date should behave similarly.
Would people be interested in a solution like this? What sort of
toggle should be used to determine if the meta-data should be
transported into an extended attribute? I'd be happy to whip up a
quick patch for this if there's a consensus on how this meta-data
should be converted.
More information about the rsync