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Question - Using dd to clone different sized disks?

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bork:

--- Quote from: Freedom Kira on May 06, 2011, 04:16:03 AM ---
--- Quote from: bork on May 06, 2011, 01:27:02 AM ---I have never used dd to clone my boot drive, used a script that mount the partitions on both existing drive and the new drive while in single user and runs dump to move.  If interested, I can provide more details.  

--- End quote ---

If I understand correctly, this does a simple data copy of all the data existing on the drive. It doesn't copy partition tables or MBR, which would mean he would have ended up with a drive that contained all the data except for how to boot. Which doesn't make for a very useful boot drive...

--- End quote ---

I did not include many details, did not know if there was much interest in an alternate method migrating from one hard drive to another. I will explain it now -

(click to show/hide)
This is a manual method of cloning your hard drive; it is the method I have used in cloning my Unix boot drives.

- write/record your existing hard drive partition information.
- disconnect the existing drive that you are cloning and install the new drive.  Before doing this, I comment out the drives that are not involved in this move out of fstab.
- do a minimal clean install on the new drive: partitions adjusted to how you want them, boot loader setup, correct OS version.  Do a boot-up test to make sure it is functional.
- reconnect the old drive, it need to be seen as the boot drive / master drive and the new disk as a secondary drive.  I will use the ad0 as the original drive and ad1 as the new drive.
- boot system into single user mode and enter the following:
  fsck -p
  mount –u /
  mount -a
  swapon –a
- check dev for the device files for the new drive, should see the partitions ad1s1a, ad1s1e … if not create the dev files.
- Make some mount points for the new drives partitions:
 mkdir /backup
 mkdir /backup/root
 mkdir /backup/usr
 mkdir /backup/var
 mkdir /backup/ (any other partitions)

I run Unix not Linux so were you see newfs, run mkfs (with appropriate options) instead.

I made this into a script:

-- script start --

#! /bin/sh

newfs /dev/ad1s1a
newfs /dev/ad1s1e
newfs /dev/ad1s1f
mount /dev/ad1s1a /backup/root
mount /dev/ad1s1e /backup/var
mount /dev/ad1s1f /backup/usr
(dump –Of - / ) | ( cd /backup/root ; restore –rf - )
(dump –Of - /var ) | ( cd /backup/var ; restore –rf - )
(dump –Of - /usr ) | ( cd /backup/usr ; restore –rf - )
umount /backup/root
umount /backup/var
umount /backup/usr

-- script end --

Swap drives, store old drive away until you are happy with the new drive.  Edit fstab.

Freedom Kira:
I still think that only migrates data without copying partition tables or the MBR, MBR being the key point here.

Useful info nonetheless, though.

bork:
It is a manual method, it does not move partition tables.  The disk partitions are created manually when you are doing the "minimal install" of the procedure on the new disk.  I sort of avoid "automated" cloning, I do not like my loss of control of what some of these methods do.  Its mostly due to my past experiences of upgrades gone bad that I do not trust them.

Freedom Kira:
The thing is, with that method you need to do an install, even if it is minimal. Using the dd command will get you a bootable disk without needing to reinstall, because it just dumps the contents of one drive onto another. Which is ideal when both disks are the same size, of course...

Edit: Problem solved. He says he ended up deleting and recreating the swap partition. I think this means he deleted the swap and extended his original partition... But whatever.

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