Backup of hd using DD.

[Xian]

On Wednesday 09 March 2005 18:02, John Pettitt wrote:
> james.cook at utoronto.ca wrote:
> >On Wed, Mar 09, 2005 at 05:13:30PM +0000, Thordur I. Bjornsson wrote:
> >>Hello list.
> >>
> >>I had an idea about using a tool similar to dd(1) take backup's of
> >>entire disks.
> >>
> >>Here's my situation:
> >>My father has an old PII running Win98 (Don't ask don't tell... he's
> >>using very old financial software ;). Needless to say the thing keeps
> >>getting borked and reinstall of his entire setup is quite frustrating.
> >>
> >>Now I was wondering if I could simply set the thing up with all the
> >>programs that he needs + drivers + anti viral &c but minus the financial
> >>software ofcourse and the rip the disk out of the machine put in my
> >>workstation make an image of it and keep it safe and when the machine
> >>goes borked I could simply rip the disk out again put it in my machine
> >>and dd the image back onto the disk and restoring the "good-image" setup
> >>(then I would restore his financial stuff with the most recent backup
> >>(wich he keeps on a zip disk).
I try to avoid taking machines of that age to bits, in case it is too much for 
them and they fail. Could you send the image across a network or something?
> >>
> >>Now my questions are:
> >>1) When I dd the image back onto the disk:
> >> What about the 'free' hd space ?
Free space compresses very well when its all zeros
> >> What about the bootloader for Win98 ?
> >> The registry &c ... ?
> >
> >The bootloader, registry and all that are on the hard disk, so if you make
> > an image of the whole thing it'll all be preserved.  The only thing I can
> > think of that you won't be backing up is your BIOS configuration, but
> > that's probably OK.
> >
> >As for free space... if you've got an 80GB hard disk and you image the
> > whole disk, you'll get an 80GB image, no matter how much free space was
> > on it.  If you want a more efficient way of doing things, I suppose you
> > could put the "base system" on a separate small slice, and just backup
> > that slice... but then you have to be careful to include the bootloader
> > as well, which might not be stored inside any slice.
>
> If you zero the disk before you do the initial install of Win 98 (dd
> if=/dev/zero of=/dev/(disk to zero) then all the freespace will be zero
> blocks which will compress really well.
>
> >>2) How do I make an image of the entire disk using dd(1) ?
> >> Or should I use some other software ?
> >
> >dd if=/dev/{disk to backup} of=/path/to/new/image/file
> >
> >where {disk to backup} is something like /dev/ad0 (for full disk) or
> >/dev/ad0s1 for slice 1, and /path/to/new/image/file is where you want to
> > put the image.
> >
> >Use the option "bs={some big number}" to dd to make it a faster (man dd
> > for more info).
I find that too big a number slows things down a bit. I use 128K with my USB 
drive, perhaps this is a point to start guessing from. I expect a bigger 
number will work better as a hard drive will be faster than USB.
>
> Make sure you use the raw disk device (/dev/adX) not a partition
> (/dev/adXsY) so that you get the bootloader.
>
>
> John
>
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-- 
/Xian

"Doing a job RIGHT the first time gets the job done. Doing the job WRONG 
fourteen times gives you job security"
unknown author