using a disk "mirrored" with dd

[Jerry McAllister]

> 
> Matt <finitesoup at gmail.com> wrote:
> 
> > I have a machine running 4.10-RELEASE-p2 with two identical hard disks
> > -- ad0 and ad2. I would like to make a complete copy of the first disk
> > to the second disk nightly for quick disaster recovery.
> > 
> > I've dd'ed the disk as follows
> > 
> > # dd if=/dev/ad0 of=/dev/ad2
> > 
> > and edited the disklabel of the second disk to change ad0s1 to ad2s1 as follows
> > 
> > # disklabel -e -r ad2
> > 
> > However, I'm still unable to mount the root partion (or any other
> > partition) of the second disk to tweak /etc/fstab etc. even though
> > 
> > # mount /dev/ad2s1a /mnt
> > mount: /dev/ad2s1a: Operation not permitted

Not an answer to your specific question, but I would suggest doing
the whole thing a little differently.

First fdisk, disklabel and newfs the drive to make the filesystems
you want, including making the slice bootable, etc.   Then copy
each filesystem on the previous disk using dump(8)/restore(8).   
If you have enough scratch space, you can dump to files in spare space 
and then restore from those.  Or, you can pipe a dump to a restore.  
It is preferable to using dd for something like this.

////jerry

> 
> What is your securelevel?  See man securelevel.
> 
> > 
> > What am I missing? Is there anything else I need to do beyond editing
> > the disklabel to allow me to use the "mirrored" disk?
> > 
> > Output of disklabel for the two disks follows:
> > 
> > # disklabel ad0
> > # /dev/ad0c:
> > type: ESDI
> > disk: ad0s1
> > label: 
> > flags:
> > bytes/sector: 512
> > sectors/track: 63
> > tracks/cylinder: 255
> > sectors/cylinder: 16065
> > cylinders: 4864
> > sectors/unit: 78156162
> > rpm: 3600
> > interleave: 1
> > trackskew: 0
> > cylinderskew: 0
> > headswitch: 0           # milliseconds
> > track-to-track seek: 0  # milliseconds
> > drivedata: 0 
> > 
> > 8 partitions:
> > #        size   offset    fstype   [fsize bsize bps/cpg]
> >   a:   409600        0    4.2BSD     2048 16384    97   # (Cyl.    0 - 25*)
> >   b:  5242880   409600      swap                        # (Cyl.   25*- 351*)
> >   c: 78156162        0    unused        0     0         # (Cyl.    0 - 4864*)
> >   e:  4194304  5652480    4.2BSD     2048 16384    89   # (Cyl.  351*- 612*)
> >   f: 10485760  9846784    4.2BSD     2048 16384    89   # (Cyl.  612*- 1265*)
> >   g: 18874368 20332544    4.2BSD     2048 16384    89   # (Cyl. 1265*- 2440*)
> > 
> > # disklabel ad2
> > # /dev/ad2c:
> > type: ESDI
> > disk: ad2s1
> > label: 
> > flags:
> > bytes/sector: 512
> > sectors/track: 63
> > tracks/cylinder: 255
> > sectors/cylinder: 16065
> > cylinders: 4864
> > sectors/unit: 78156162
> > rpm: 3600
> > interleave: 1
> > trackskew: 0
> > cylinderskew: 0
> > headswitch: 0           # milliseconds
> > track-to-track seek: 0  # milliseconds
> > drivedata: 0 
> > 
> > 8 partitions:
> > #        size   offset    fstype   [fsize bsize bps/cpg]
> >   a:   409600        0    4.2BSD     2048 16384    97   # (Cyl.    0 - 25*)
> >   b:  5242880   409600      swap                        # (Cyl.   25*- 351*)
> >   c: 78156162        0    unused        0     0         # (Cyl.    0 - 4864*)
> >   e:  4194304  5652480    4.2BSD     2048 16384    89   # (Cyl.  351*- 612*)
> >   f: 10485760  9846784    4.2BSD     2048 16384    89   # (Cyl.  612*- 1265*)
> >   g: 18874368 20332544    4.2BSD     2048 16384    89   # (Cyl. 1265*- 2440*)
> > 
> > Thanks for any insight, and let me know if you need to see anything else.
> > 
> > -Matt
> > _______________________________________________
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> 
> 
> -- 
> Bill Moran
> Potential Technologies
> http://www.potentialtech.com
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