[CentOS] How to copy a system?

Thu May 5 14:10:52 UTC 2011
ken <gebser at mousecar.com>

On 05/05/2011 08:01 AM Brunner, Brian T. wrote:
> centos-bounces at centos.org wrote:
>> At Thu, 05 May 2011 07:44:52 -0400 CentOS mailing list
>> <centos at centos.org> wrote: 
>>> On 05/05/2011 07:13 AM, Timothy Murphy wrote:
>>>> Is there a standard way of copying a working system
>>>> from one machine to another with different partitions?
>>> You could also utilize cloning software, such as the client version
>>> of drbl, clonezilla livecd. 
>>> You could also do a direct copy with dd onto a connected drive.
>> Warning: dd is not a good choise if the source and desination
>> drives/partitions are *different* sizes.
> Different block mappings will also give you grief.
> .:. The drives must be identical manufacturer and model, down to the
> firmware revision.
> dd is not a backup tool in the general sense.

I had doubts about dd also.  But last year, when I needed to upgrade to
a larger drive, I used it and it worked fine.  I bought a new drive (of
course of larger size... different manufacturer too), put it into a
drive enclosure, plugged that new drive into my USB port, and ran dd to
copy the entirety of hda to hdb.  Shutting down the machine, I swapped
the hard drives and booted with the new drive and-- viola!-- new bigger
drive with everything running just like on the old drive.  I didn't have
to reconfigure anything; even the networking worked on the new drive
without touching anything.  The only thing I did on the new drive was to
create a new partition from all the extra new hd space I had.  Indeed,
this is a multi-boot machine and all OSs on it copied over just fine.
In addition, all my linux partitions are encrypted, and all that copied
over perfectly as well.

One tip: Use dd's smallest block size (BS).  I did this copy using dd
several times, starting with 4k, then 2k block sizes and the new disk
had problems when I tried to use it.  IIRC, I had to rachet down to 256
to get a working drive.  And this took eight or ten hours to copy an 80G

Another tip: in your BIOS the parameter for the hard drive should
probably be Auto-Detect if your source and destination drives aren't
identical.  That's generally the default anyway.

Final tip (I think):  For me, my machine A and machine B were the same
machine... so of course the hardware was absolutely identical.  Using dd
might not work if the hardware on A and B are too different from one


"Truth is the most valuable thing we have, so I try to conserve it."
	--Mark Twain