Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!labrea!agate!ucbvax!mit-richter.UUCP!krowitz
From: krowitz@mit-richter.UUCP (David Krowitz)
Newsgroups: comp.sys.apollo
Subject: Re: Wanted: Apollo RBAK info
Message-ID: <8802180452.AA22187@EDDIE.MIT.EDU>
Date: 18 Feb 88 02:18:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 57

The UNIX tar tape is a completely different format than
the ANSI tape format. Each file on an ANSI tape comprises
three physical files -- a short ascii header which contains
the name of the file, the record and block sizes, etc; the
actual data of the file written with the record and block
sizes specified in the header; and a short ascii trailer
which contains some of the info from the header and also
notes whether the file is complete or whether it continues
onto a second tape. The actual data in an ANSI tape file can
be almost anything. You can write one disk file to each ANSI
tape file and give the tape file the same name as the disk
file. The VAX/VMS command 'copy dsk:*.ftn mta0:' will copy
all of the fortran files from the current directory to the
tape - one file per ANSI tape file, with the file name in
the header the same as the file name on the disk. You can
then use RWMT -I to index the tape, see all of the file
names  and the block and record sizes, etc. RWMT -R -ANSI
will read such a tape just fine. On the other hand, what
WBAK/RBAK does is to take all of the disk files that were
specified and pack them up into a single ANSI tape file
which includes their ACL's, time/date of creation, etc.
The ANSI file header contains the name of the backup set
as the name of the tape file. The trailer notes whether
the backup set fit onto a single tape or continued onto
a second tape. Since each ANSI tape file is an entire
backup session, it's easy to put another backup set into
the second (or third, forth ...) ANSI file on the tape.
If you use RWMT -I on a tape created by WBAK, the files
you'll see are the complete backup sets on the tape (ie.
the first tape file is WBAK -F 1, the second is WBAK -F 2,
etc.) and the file names shown are the names of the backup
sets as specified with the WBAK -FID switch, not the names
of the files that were backed up (which are embedded in the
data of the ANSI tape file). The tar format is a completely
different format. It is not ANSI compatible. It can not
span more than a single tape. There are no header and trailer
files which can be used to name the backup set. The ANSI tape
format is operating system independent. The tar format is
used only by Unix systems. For system backups, most Unix
systems use the dump/restore programs, since these can
handle multi-tape backups. Unfortunately, dump backs up an
entire disk partition, not just the files and directories
you specify. Tar on the other hand will back up only those
files you want backed up, but since it can't handle multi-tape
backups it's pretty unless for system backups. WBAK/RBAK gives
you the flexibility to do both, but you can't talk to a Unix
system. It's kind of frustrating.


 -- David Krowitz

krowitz@richter.mit.edu   (18.83.0.109)
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mit-erl!mit-richter!krowitz@eddie.mit.edu
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