[ILUG] backup

[Niall O Broin]

On 25 Jun 2005, at 17:07, Paul Biggar wrote:

> I need to backup my system, and searching google gave significant
> information overload. I don't need incremental backups, don't need it
> to fit on CD-R, and want to get everything (except partition info, i
> can do that manually, although if its easy...).
>
> I have a load of partitions, all reiserfs, and want to copy them to my
> windows partition while I wait for my new HD.

Wow - you use reiserfs. And on a dodgy hard disk too. You like to live 
dangerously.

> I was thinking the easiest thing to do is:
> cat /dev/sda2 > /mnt/windows/sda2.backup
>
> and then, when the new disk comes in:
> cat /mnt/windows/sda2.backup > /dev/sda2
>
> and maybe add a pipe to bzip2. Will this work? Is there something I'm
> missing which explains  the need for cpio/tar etc?

It will work, but it leaves you very dependent on matching partition 
sizes etc. Much more generally useful to do something like

tar czf /home /mnt/windows/home.tar.gz

you could use cjf on anything resembling a modern Linux to use bzip2 
compression instead of tar. You might get 5-10% better compression at a 
cost of much much longer compression times.

Niall

P.S. I was curious, so did a little experiment.

Files		Size		gzip	size / time	bzip2 size / time

/boot		6616KB	5736KB / 4.3s		5784KB / 23.8s
/var/log		15576KB	4048KB /	5.8s		3500KB / 61.1s


So depending on your data, bzip2 MAY compress better, but is always 
much slower. The two examples I chose probably showed opposite ends of 
the spectrum in compressibility.