Only one backup per tape? Really?

[Ronald S H Khoo]

nelson at clutx.clarkson.edu (aka NELSON at CLUTX.BITNET) writes:

> I've got two filesystems to back up, and only one tape drive, and I'd
> like to do unattended backups.  Can I really only back up one
> filesystem per tape?  Well, of course I mean, will I be able to *restore*
> from a tape with two backups on it?

Depends on what kind of tape drive you have.

If it's an Irwin drive or something like that which does not support a
non-rewinding device, then NO.

If it's a QIC-02/QIC-24 thingy sure, why not?  Judicious use of the
non-rewinding device (/dev/nrct0) and the "tape rfm" command will get
you most places.

Of course if there's an error *anywhere* on the tape, you can't skip
past it, so if the first archive is busted, you can't get at the second,
but that's a generic problem with cartridge tapes in general.

BTW, if you're serious about doing unattended backups like that, I
recommend getting the UFM (a.k.a.  xnx155b) update from SCO because
there's a much better cpio there -- the Xenix dumprestor isn't really
much good, so I recommend cpio.  Also, there's a better cartridge tape
driver in UFM.

What I don't understand about unattended backups is, how do you get all
the users processes off the filesystem ? Or do you risk backing up a
live filesystem?  In that case *definitely* don't use the Xenix
dumprestor -- it gets very confused real easily in a completely
unrecoverable way from inconsistent backups (and from consistent ones as
well, I think)
-- 
ronald at robobar.co.uk +44 81 991 1142 (O) +44 71 229 7741 (H)