Re: [gentoo-user] backup to a cold-swap drive

[Frank Steinmetzger]

Am Mittwoch, 28. April 2010 schrieb Iain Buchanan:
> Hi,
>
> A winblows colleague said he uses a utility to backup his internal hard
> drive to an external disk, such that if his internal disk fails he can
> replace it with the external disk and continue straight away.
>
> Since I go to weird locations with unreliable power and sometimes drop
> my laptop I thought it should be simple to do the same in Linux.  I have
> an external disk the same size, but now what?
>
>       * I want to copy changes intelligently (ie. no dd, gparted, or
>         Ghost4Linux).
>       * I want to copy a specific device only (no usb keys, etc) to a
>         specific external device.
>       * Windows partitions can be ignored.
>       * It doesn't matter if the copy is not unmounted properly, eg. if
>         power is shut of without shutting down.
>       * The external disk must be able to be absent
>
> Can md use one internal and one external disk in a RAID 1 setup, with
> the external disk not always there?  Any other suggestions?

After I upgraded my laptop with an internal HDD of 500 GB, I started using my 
old external 500 GB drive as backup. Though of different dimensions and 
makers, they both have the same number of sectors. So I dd'ed the entire disk 
first, which gave me an exact mirror of the internal disk. I though this would 
be faster, because I have lots of small files in some places.

But now I can update the backup by a simple call to rsync:

rsync -aX --delete / /dev/<backup root partition>/

-a (archive) copies permissions, ownerships and the likes
-X stops at file system boundaries, i.e. it will only backup the actual root 
partition, without other mounted file systems such as /proc, /dev and /home.
-- 
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Why did the tachyon cross the road?
Because it was on the other side.