[Gllug] multi tape backups

[Alain Williams]

I am trying to get multi tape backups to work.

There are 2 sorts of archive that I want to write: full archive (2 tapes worth (today))
and incremental (will all fit on one tape).

I first of all used (GNU) tar, this handles multi tape backups reasonably nicely.
In particular the 2nd tape starts with a tar file header that says that this is the 2nd
part of a file. The trouble is with incremental backup: I use --newer-mtime to not copy
old files -- but it doesn't apply the test to directories, so I get zillions of old/unchanged
directories on the tape -- this I would rather avoid.

Cpio avoids the directory problem (feeding it the output of find -newer reference_file).
However the second tape just starts where the first left off -- there is no header,
the result is that when I read the second tape back in (without having first read through
the first one) I get a message like:
	cpio: warning: skipped 5276 bytes of junk
Cpio seems to resynchronise by looking for a cpio header in input!
That might work most of the time, but what if the end of the last file on the previous
tape contains a cpio header ... cpio will resynchronise badly.

Both will prompt the user to insert the next tape, that sort of thing is not a problem.

I don't want to use tar for full backups & cpio for incremental.

Anyone got any suggestions ?

(I suppose that the best way would be to fix GNU tar)

-- 
Alain Williams
Parliament Hill Computers Ltd.
Linux Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer.
+44 (0) 787 668 0256  http://www.phcomp.co.uk/

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