Re: [Bug-tar] Issue with GNU Tar and HP-UX LVM v2.2 filesystems

[Nathan Stratton Treadway]

On Thu, Sep 27, 2012 at 20:05:38 +0000, Michael White wrote:
> I am trying to get GNU Tar to do incremental backups and am running
> into a hard error.  I've been using GNU Tar on my HP-UX systems for
[...]
> but when I go to run the incremental I get this error.
> 
> Unexpected field value in the snapshot file
> Error is not recoverable: exiting now
> 
> I got the tar-snapshot-edit utility and it calls out this file system.
> 
> Director: /cghbck
>                 Dev value too high: "18446744071562076161" > 4294967295


On Mon, Oct 01, 2012 at 15:10:21 +0000, Michael White wrote:
> One of you talked about signed values.   And that does appear to be
> the case.  See my output below using the above perl command.  The
> filesystem created as a HPUX LVM 2.2 does show a sign whereas the 1.0
[...]
> -2147475455            dev_t      st_dev       ID of device containing file


Note that this seems to indicate that dev_t is actually signed on
HP-UX... which means that tar-snapshot-edit isn't strictly correct for
you, since it uses "max" values for the fields taken from Linux (where
dev_t is unsigned).  Though happily it was "close enough", in that
it seems to have flagged the field that was causing you trouble...


Sergey/Paul, 

Although the existence of the -c option to tar-snapshot-edit does make
it less urgent, Michael's case is another example where it seems like
checking the values as they are being written and/or giving more
information in the "unexpected field value" messages would have been
helpful, as I wondered about in:
  http://lists.gnu.org/archive/html/bug-tar/2009-03/msg00069.html

Pehaps if you are making changes to those routines in order to support
signed dev_t, some of those improvements might be easy to add as well.

(Though I would amend my earlier proposal to have the two messages say
something like
  Unexpected field value in snapshot file: "<FIELD>" below minimum of <MIN>
and 
  Unexpected field value in snapshot file: "<FIELD>" above maximum of <MAX>
, respectively.)

Thanks.

                                                        Nathan 

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