Restoring Data from a DD image

Gayn Winters gayn.winters at bristolsystems.com
Thu Oct 6 14:24:10 PDT 2005



> -----Original Message-----
> From: Bill Schmitt (SW) [mailto:software at schmittnet.com] 
> Sent: Thursday, October 06, 2005 1:16 PM
> To: gayn.winters at bristolsystems.com
> Cc: questions at freebsd.org
> Subject: Re: Restoring Data from a DD image
> 
> 
> Gayn Winters wrote:
> 
> >>-----Original Message-----
> >>From: owner-freebsd-questions at freebsd.org 
> >>[mailto:owner-freebsd-questions at freebsd.org] On Behalf Of 
> >>Bill Schmitt (SW)
> >>Sent: Thursday, October 06, 2005 11:11 AM
> >>To: questions at freebsd.org
> >>Subject: Restoring Data from a DD image
> >>
> >>
> >>I've just replaced a hard disk that was dying fast. I've 
> done a full 
> >>installation of 4.9 (later releases won't install, which I've 
> >>submitted 
> >>a problem report on already). The old disk is connected but 
> >>not mounted. 
> >>Searching around, I found some suggestions to try to read the 
> >>old disk 
> >>to restore what I can and I used dd to copy what could be found (dd 
> >>-if=/dev/ad0s1e of=/usr/olddsk/oldimag.dmg 
> conv=noerror,sync) and it 
> >>seems to have copied the file. Now, I'm a little stuck. Can 
> >>someone help 
> >>me understand how do I mount that image somewhere to browse 
> >>it and copy 
> >>what I can from it? If I'm not going about this the right way, I'd 
> >>appreciate other suggestions
> >>
> >>    
> >>
> >
> >I'm a little confused:
> > 
> >Did you try to copy (dd) the old disk before you did a new install?  
> >If so, to where?
> >
> >Is /dev/ad0 your new disk with the fresh 4.9 installation on 
> ad0s1? Or
> >did you just add a new disk as /dev/ad1 and did the fresh install on
> >ad1s1?
> >
> >Is your unmounted old disk /dev/ad0 or /dev/ad1 now?
> >
> >I'm guessing that ad1 is your new install, ad0 is not 
> mounted, and you
> >were able to copy ad0s1e to oldimag.dmg with the above dd 
> command.  If
> >so, continue. If not, send a correction.
> >
> >Why not try 
> >   mount -r -t ufs /usr/olddsk/oldimag.dmg /mnt
> >   cd /mnt
> >   ls
> >
> >I ***think*** mount will do this.  If not, try dd'ing 
> oldimag.dmg to a
> >spare slice, e.g. if you created /tmp as /dev/ad1s1e, then you could
> >   dd if=/usr/olddsk/oldimag.dmg of=/dev/ad1s1e
> >   cd /tmp
> >   ls
> >
> >Good luck!
> >
> >-gayn
> >

> Sorry, when I first decided to try FreeBSD, I had a 4.7GB as 
> the primary 
> on ad0 and moved usr to ad1 when I added the drive that 
> ultimately went 
> bad (a 60GB) as ad1. When I had to do a full installation 
> again, I put a 
> new drive (80GB) into place where the 4.7GB drive was and 
> started from 
> scratch with ad1 disabled. So, now I'm booting from the new drive and 
> have used dd to copy whatever is found on the damaged ad1 to 
> an image on 
> ad0. It's after that I get stuck. I've looked at the man page 
> for mount, 
> but  I haven't seen anything specific to an image. I tried your 
> suggested mount command, but it responded "Block device required". I 
> suppose I can try to dd back to the 4.7GB drive that I would 
> now mount 
> as ad1. We'll see what happens.
> 
> Thanks,
> 
> Bill
> 

As Joe S suggests, use mdconfig or vnconfig to create the block device,
then mount works. (I tried it with mdconfig using 5.4.) Dd'ing to a
spare slice or partition will surely work as well.  

-gayn




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