[plug] Recover a backup

[Daniel Pittman]

Anne Busby <anne.busby at gmail.com> writes:

> A client has a full backup from a Pronto Linux system, but the start
> of the tape has been overwritten by someone starting a backup and
> aborting it. The data that needs to be retrieve is believed to be on
> the part of the tape that is after the area that was overwritten.
>
> dd gets to the end of the aborted backup and no further. We don't have
> any details of the command use to create the backups.
>
> Any ideas on what we can try?  I believe it is the only backup.

Pay a data recovery company; since you only need to read data past the
(logical) EOD marker on tape you shouldn't have to pay very much.

Otherwise this is extraordinarily hardware dependent, and pretty much
every solution other than "use vendor software[1] to bypass the EOD mark"
is going to run a significant risk of making things worse.

Seriously, just pay someone.

Regards,
        Daniel

The EOD marker is detected and acted on in *hardware*, not software, so
you need to do something drive specific to bypass it.

Footnotes: 
[1]  ExaByte used to offer a tool to switch to "directory mode" that
     could, in some cases, bypass the regular EOD mark, but only on
     ExaByte drives.