Using dd to Make a Clone of a Drive
Ken Stevenson
ken at allenmyland.com
Fri Feb 10 07:27:20 PST 2006
Giorgos Keramidas wrote:
> On 2006-02-09 14:36, Martin McCormick <martin at dc.cis.okstate.edu> wrote:
>> After installing FreeBSD5.4, the ISC dhcp server and ISC bind
>> on a hard drive, I wanted to clone that drive to a second drive so as
>> to generate a second server, using what I had already installed as a
>> template. I used the following command:
>>
>> dd if=/dev/da0 of=/dev/da1 bs=512
>>
>> It turns out that dd defaults to 512-byte blocks so I didn't
>> really need the bs=512, but I am not sure I haven't made some other
>> type of mistake. The dd command has been running for about 4 hours on
>> a very fast system, with a 1-gig processor, 1 gig of RAM and two 31-GB
>> drives. One would think it should have finished by now, but it is
>> still running. Is this a valid method of copying the entire contents
>> of one drive to another? Thank you.
>
> Bah! That's too slow for my taste. I would usually go for a newfs,
> dump, and restore option. For instance, to create a copy of /usr on a
> second disk:
>
> newfs -U /dev/ad1s1a
> mount /dev/ad1s1a /mnt
> dump -0 -a -L /usr | ( cd /mnt ; restore ruvf - )
>
> Copying with dd(1) is not as fast :)
>
I had to clone a couple systems a while back, and I also did it with
dump/restore. The best part was this was the first time I actually
restored my backups to a bare hard drive. It gave me a lot of
confidence that my backups actually work. I think a lot of people find
out too late that whatever backup solution they're using is flawed and
they can't rebuild their system from it.
--
Ken Stevenson
Allen-Myland Inc.
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