Doin' the backup

I've finally convinced myself that a) I should backup, and b) it's not all that expensive. Following jwz's advice, I bought myself a drive, stuck it in a USB enclosure and ran the backup command. After that was all finished I realised I had to disconnect the drive. This is where things got a little tricky. If I was running OSX or Windows, I could use the standard eject command (remove hardware on Windows); the disc would be unmounted, stopped, and (possibly) turned off. I wasn't too worried about turning the disc off because that happens when the plug is pulled. I also wasn't too worried about unmounting the disc because I know how to do that. What I was worried about was spinning the disc down.

When power is cut to a typical hard disc, one of two things happens. First, the head will just sit there between the platters, and if you shake the drive or drop it (or whatever), then the disc will get scratched and you will lose data. Second, (preferably) the head will perform an emergency retraction and get itself out from between the platters. This is a good thing because it means that it won't stay in there and delete your precious bits, but it's still not ideal because there is the potential for it to scratch your disc on the way home. So, ideally, the disc should be stopped before the power is removed.

But, in this case, I'm not running OSX or Windows - I'm running Linux, and Linux doesn't have a simple, built-in, all-in-one solution for this.

The first program I tried was scsiadd. Random Bits has a pretty good post on scsiadd, and I was hopeful, but I found that, for whatever reason, it didn't work for me.

sdparm is what I was looking for, and it works like a charm.

As a side note, I probably should also suspend the USB port as Yan Li suggests, but my kernel doesn't like that so I didn't bother.

The script that I've settled on (for now) is:

#!/bin/sh

mount /dev/sdb /media/backup

rsync -vaxE --delete --ignore-errors / /media/backup/

umount /dev/sdb

## spin the disc down
sdparm -C stop /dev/sdb

## wait for disc to spin down
sleep 10

echo "Done"

I'll probably add a few more lines to check stuff like whether something is actually at /dev/sdb but this script already does pretty much everything I need it to.