Re: [linux 2.6 patch] ext2 support for hurd extensions via xattr interface

[M. Gerards]

Quoting Roland McGrath <roland@frob.com>:

> This makes it possible to use a GNU/Linux system to not only create but
> also populate a Hurdish ext2 filesystem complete with passive translator
> settings so that it can boot the Hurd normally.  It also makes it possible
> to back up and restore a Hurdish ext2 filesystem from a GNU/Linux system,
> using any tools that understand the extended attributes.  (Off hand the
> only such thing I'm aware of is `star', which I have not tried using
> myself.)  Basically, the ./native-install bootstrapping is right goofy and
> one shouldn't have to do things that way.  I would much prefer to have a
> bootstrap gnu.star in the extended format so it unpacks from GNU/Linux
> directly into a complete GNU/Hurd filesystem with /servers and /dev intact.

GNU tar also supports POSIX  archives since some months.  I wrote a patch for
GNU tar to support passive translators (GNU.translator).  It should not be too
hard to support this on GNU/Linux as well.

You can find this patch in the bug-tar@gnu.org mailinglist archives, but
I will send this patch for review to bug-hurd soon.
 
> If people find this useful, then I can try my luck at getting this
> incorporated into Linux.  Unfortunately, the code in question does not lend
> itself to making an isolated module instead of modifying the kernel
> directly.

I find this very useful.  If my tar patch will be applied I can add support
so it can create and extract archives with passive translators on GNU/Linux.
 
> If we settle on this allocation of gnu.* xattr names, then another thing I
> can do is make the *xattr functions in libc on the Hurd present synthetic
> gnu.author and gnu.translator attributes.  The benefit of this is that
> archivers like star will just work out of the box to save and restore the
> author field natively on Hurd filesystems the same way they work on Linux
> writing Hurd filesystems.  This is probably not so useful for
> gnu.translator, since the *xattr libc interfaces don't have the semantics
> of O_NOTRANS lookups.  However, if e.g. a "notrans" translator were used
> for making backups or other archives, then star running on that would
> automagically save and restore passive translator settings as you'd want.

That would be really nice.

Thanks,
Marco