Re: [Sheflug] Tape drive - backing up software?

["Chris J/#6" <nospam [at] nccnet.co.uk>]

> Hi guys, got another annoying newbie question for you that the suse manula has been fairly unhelpful with...
> 
> ive just got hold of a old HP Surestore 5000 dat drive and ive got it installed right via scsi, its showing up as /dev/nst0 through xscsi, however im not sure how to use to back stuff up...
> 
> basically , i have a 20gb data drive in my computer and i want to be able to back it all up should the worst happen someday - bearing in mind that the largest disks my thingy can take are 90m/2gb uncompressed, how can I do this? I read in an old linux magazine that "dump" might be able to help me, but it wasnt too specific and i dont like commmand lines (im sure that'll change at some point...)
> 

The tape may be a 2GB/90m tape, but if the drive is a DDS-DC rather than a 
plain DDS, then you'll have some form of compression on the tape as well. The 
compression used in DDS is quite good and can achieve high ratios.

dump isn't really a useful tool for what you want to do - especially as you 
don't really have the tape space - as it can only back up entire partitions, 
rather than groups of files (its partition based rather than file-system 
based).

I don't know what programs like Amanda are like - I tend to backup using the 
old faithful 'tar'. It's basic operation to backup would be:
	tar cvf /dev/st0 <files>

Note: I use st0, rather than nst0. The 'n' device is the same as st0, except it doesn't rewind the tape. Useful if you want to use one tape for multiple dumps or multiple tars, gets in the way (meaning you need to issue an mt rewind) otherwise.

So firstly - decide what you want to back up. You won't need everything (why back up /usr/bin/ls when it can be recovered of installation CDs?)...I tend to backup configuration and home directories (ie, /etc and /home), and do this with a simple invocation:
	tar cvf /dev/st0 /etc /home

To extract a backup you'd use 'x' rather than 'c':
	tar xvf /dev/st0

OR to only pull back certain files:
	tar xvf /dev/st0 <file(s)>

That's the basics. I've got a nice complex backup script at work (well, a few actually) to deal with extras like tape-changers and backing up windows boxes by combining everything with smbtar.

Now -- a nice shortcut -- I think tar will default to st0 if you don't specify a file (I *know* it defaults, I j ust can't remember the default off top of me head), so you could shorten the tar invocation to:
	tar cv /etc /home
and
	tar xv <optional file spec>

or if you don't want to see any progress output:
	tar c /etc /home
and
	tar x <optional file spec>

Tar works well - for simple backups, its all that's needed (for complex backups its all you need as well after it's been wrapped up in a script). Amanda and the like are basically front-ends to tar and similar tools (tar is considered outdated by some people for backups, preferring cpio instead. I don't like cpio and have never had a problem with tar).

Oh - if your tape drive doesn't have compression, then tar on Linux boxes is the GNU version (cunningly enough), and you can ask tar to do on the fly compression by specifying 'z'. eg,
	tar zc /etc /home
and:
	tar zx

Chris...


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