Using pre2 for backing up a mac

Wesley W. Terpstra terpstra at
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  
extended attribute.

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.

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