[ACL-Devel] tar file format?

[Andreas Gruenbacher]

Michael Tokarev wrote:
> 
> Does anybody knows how the acl entries should be represented
> in tar?

The Posix 1003.1e working group did not issue any recommendations. To my best
knowledge, there is an improved format being worked on (see the Austin group,
<http://www.opengroup.org/austin/>). I don't know anything about the status or
the area they will cover. There are also some other issues to be resolved,
including maximum file size (there's a limit in tar that's reachable today, for
example).

Who knows more about this?

> I tried to reverse-engeneering this on solaris (2.6),
> but it's tar is simple buggy -- it does not clears the buffer
> before filling it up with acls, and there is always a garbage
> at the end, so I even can't recognize the end of acl block...
> I want to try to implement a patch to gnu tar for acls.

There are also proprietary extensions on HP-UX.

If you're serious about extending GNU tar you should talk to Paul Eggert
<eggert@twinsun.com>, the mantainer of paxutils. Also, some people on this list
might have some ideas about it.

At least those extensions should cover all of Posix 1003.1e DS17 plus ext2
attributes (and other proprietary extensions).

> And some related questions:
>   format for cpio?

The same. No "official" extension to the cpio format.

>   format for dump (this last one may be urgent for acl usage)

Doesn't matter much. Dump is ext2 specific, so it can be extended rather easily.

You can use getfacl -sR to get all a list of ACLs in a sub-tree. I'm currently
using find + getfacl to back up one production server. This isn't pretty, but it
works. (Restore is via setfacl -B). Of course, this currently only works with
the Linux ACL utilities...


Andreas

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 Andreas Gruenbacher, a.gruenbacher@computer.org
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