> Up until now I've been using 'tar' to archive/backup select user
> files plus certain system and program files. I would like however to
> start doing full system dumps as an extra bit of insurance. I've
> surfed around some but some of the info seems contradictive so I'd
> like to know what others are doing. I was thinking it might be nice
> to use a spare drive as the backup storage. Its my understanding
> that 'dump' and 'restore' work on _raw_ devices ; does this mean I
> ought to be able to, for instance, hook up my eternal scsi drive to
> my Sparc and just do 'dump -F -f /dev/rsd1c /' w/o having to worry
> about mounting or filesystem issues?
No, it doesn't work like that. If you're sending the output of dump
to a disk, then the output has to go into a file in the Unix file
system. So you'll need to mount your external SCSI disk before
dumping to it.
It also looks like your dump command line is incorrect. Assuming
your external SCSI was mounted as /mnt/external, the command line
should probably be something like:
dump 0sf 1000000 - / | gzip >/mnt/external/root.dump.gz
The leading "0" is the dump level-- zero means do a full backup.
"s" is the "size" (length) of the dump media, which we're setting
to 1000000 here. This is a relic of old disk-to-tape dumps where
you might span multiple tapes. Since your dump media is big enough
to hold the entire archive, we're just specifying an arbitrarily large
value (1000000) to avoid dump trying to make multiple archives.
"f" specifies the dump file, which we're setting to "-" (standard
output) so we can shove the whole thing through gzip for compression.
Actually the GNU dump program that comes with most Linux distros has
built-in compression support via the -z (gzip) or -j (bzip2) options,
but I'm in the habit of doing the "pipe to gzip" routine for
portability reasons (I work on lots of non-Linux systems).
The last thing you specify is the _partition_ you want to dump. This
is not like the tar command-- dump works on a partition by partition
basis. So the above command would dump your root partition only. If
you have separate partitions for /boot, /usr, /var, et al then you'll
need to dump each one individually.
> I also read that one should always be in
> single-user mode when running dump/restore - is this always required or
> just with certain filesystems and/or dump options?
The issue here is that dump is a "two pass" archiving method. First
it dumps the directory structure, and then it dumps the individual
files. If the file system changes significantly in the middle of the
dump, the whole archive may become corrupted and the dump is then
useless. Hence, the recommendation is to always dump in single-user
mode so that the file systems won't be changing while you're dumping
them. Many sites do dump in multi-user mode, but late at night when
the system isn't being used.
Frankly, using GNU tar is probably a better option precisely because
it doesn't have this particular issue (tar is a "file at a time"
archiver, and is therefore relatively resistant to file system changes
during the archive process). And GNU tar can deal with various
"weird" files (sparse files, device files, etc.) that other versions
of tar tend to have trouble with.
--
Hal Pomeranz, Founder/CEO Deer Run Associates [EMAIL PROTECTED]
Network Connectivity and Security, Systems Management, Training
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