On Sat, May 26, 2007 at 09:50:41PM +0200, Pfenniger Daniel wrote:
> Keith Lofstrom wrote:
> >Thanks for SL5!
> >
> >I am currently upgrading two systems from SL44 to SL5 (the rest
> >are getting fresh installs).
> ...
> >I do each upgrade on a "dd" copy of the original hard drive onto
> >a spare;  backing out of a failed upgrade is easier that way.
> 
> The "wisdom" I have gathered is not to use dd for such
> disk duplication, but to use fdisk for partitioning, and
> "rsync -ax /orginal/ /target/" for file copy
> (be careful with the trailing /'s).
> 
> The first reason is that dd copies bad blocks, and
> the second reason is that rsync over a blanck partition defrags the 
> files.  A second rsync allows to check fast the first copy.  The third 
> argument is that often disks are not strictly equal, and
> then dd is anyway not recommended.
> 
> Some use tar instead of rsync.

I do this with two identical, modern drives, which seem to internally
manage the bad blocks.  The problem with rsync is that it sometimes
does not copy metadata properly - even the mod dates for softlinks
are not properly set.  tar is less capable than rsync.  

Also, this way I get identical bits for the boot blocks.  Otherwise
I need to fool around with grub.  I can do the copy in about 5
minutes of setup (mostly booting to single user and doing a sync
first), two lines of typing, followed by a copy time of one hour
per 150GB or so.  The rsync approach involves a lot more setup and
fiddling, even with automated scripts.

Indeed, I used rsync and the automated approach to merge partitions.
I missed a few things, and had to do it a couple of times to remember
to find every bit of data, and to exclude things like /sys and /dev
and /proc and /media (and of course the target drive) .  

Either way, it is important to use identical drive models.  There
should be identical spare drives anyway, because someday you will need
to restore a backup to one, and that should be practiced beforehand.

Keith

-- 
Keith Lofstrom          [log in to unmask]         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs