[Bug-tar] Changing 'dev' in snapshot files?

[dustin]

Please see the discussion that has led up to this at
  http://tech.groups.yahoo.com/group/amanda-users/message/62562
and accept my apologies if it's come up before -- a quick scan of the
archives didn't turn anything up.

Briefly, the Linux kernel is soon going to change the major device
number for LVM.  This is basically invisible to users, except that the
device number is stored in tar snapshot files (src/incremen.c), and when
it changes, the snapshots no longer match the files on disk.  For users
of Amanda, the result is that, after the upgrade, all partitions must be
backed up in level 0 (non-incremental) mode.

We quickly dismissed the idea of changing 'tar' to ignore the device
number -- there are lots of legitimate reasons to keep that.  However,
it would be very useful to have a quick way to *modify* existing
incremental files to reflect a new device number.  For example,
  edit-snapshot-dev 0xfe00 0xe800 /path/to/snapshot/file

So my questions are:
 - is this a ridiculous idea?
 - does something like this exist in someone dev's ~/tmp directory?
 - if not, and if I write something, do you want to host it (e.g., in
   contrib/)

Dustin

-- 
        Dustin J. Mitchell
        Storage Software Engineer, Zmanda, Inc.
        http://www.zmanda.com/