SUMMARY: Problems with tape backup

From: Eric Bonharme (
Date: Tue Mar 11 1997 - 09:53:53 CST

The problem, as stated, was:
--start of problem--
We run a standalone server running Solaris 2.5.1 on Intel. We recently
attached an HP JetStore 6000 C1533 tape backup system.

The /dev/rmt/ director lists the appropriate devices. No problems there. I
want to do a full system backup, initially and then dayly updates. (This is
a remote system, no physical access).

I started using
 tar -fu /dev/rmt/0c /
But this resulted in tar trying to back /dev/rmt/0 and swap size overflow -
no good. (The tapes are supposed to take 8 Gig, and we only have 4Gig of

So I tried
 tar -fu /dev/rmt/0c /var /export/home /opt /usr
I still run out of space, but something funny seems to be happening.
If I do a tar -ft /dev/rmt/0c, all the files in /usr are listed, but then
it starts again at //usr.
--end of problem-- (well...)

Thanks to all who have responded:
Mike Schmidt <> (Niall O Broin - Gray Wizard)
"Birger A. Wathne" <birger@Vest.Sdata.No>
Tim Evans <>
Tim Thompson <>
Fedor Gnuchev <>
cde@Fax.COM (Christian D. Evans)

and especially Rich Kulawiec <>

The general consensus is that using tar for tape backups is a bad idea.
usfdump/usfrestore should be used instead, for the following reasons:

1. tar has a 100-character pathname limit,
2. tar does not cope with special files/devices,
3. tar has no code to deal with active filesystems.
4. it does not give you a backup that you can easily restore
5. tar can't cope with the entries in /dev.

I was worried that the manual pages state that ufsdump should only be run
on an inactive filesystem, but apparently, this is only a recommendation
and the failure chace is indeed very low.

Acconding to Birger A. Wathne, the commands for a full backup go something
        ufsdump 0f /dev/rmt/0cn /
        ufsdump 0f /dev/rmt/0cn /usr
        ufsdump 0f /dev/rmt/0cn /var
        ufsdump 0f /dev/rmt/0cn /opt
        ufsdump 0f /dev/rmt/0cn /export/home
but some people prefer to back-up physical devices (/dev/dsk/...).

Rich Kulawiec will post a summary of this and other tape backup issues
later on this evening (EST).

Thanks again, it's been a very 'knowlegdge-enhancing' day.

Eric Bonharme

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