[Bug-tar] checksum request

[T. Horsnell (tsh)]

We were recently saved from a small disaster by
gnutar's --diff option. An archive written to tape
had tape errors which did not produce any hardware
errors on readback, and were presumably the result
of some bad writes. The errors were only discovered
because a paranoid user had used the --diff option
before choosing to delete the original files.

However, the option to use --diff is not always
available, (all our system backups have to be done
online, and files therefore may change) so I wonder
whether it would be possible to add an option to
tar to make it checksum the archive as it is reading
or writing it, and to output this checksum to
stderr at completion. Thus an archive's integrity
could be checked by saving the checksum output
during the tar -c step, and comparing it with the
one produced during a tar -t step (assuming tar -t
reads through all the files in the archive).
It would then not be necessary to refer to the
original files at all. Is this a possibility?


Regards,



Terry Horsnell (address@hidden)
I.T. Manager
Medical Research Council
Lab of Molecular Biology
Hills Road
CAMBRIDGE CB2 2QH
U.K.
Phone:  +44 (0)1223 248011
Fax:    +44 (0)1223 213556