how to boot from a backup disk created by dd

Question

I use dd command to backup a disk.

# dd if=/dev/sda of=/dev/sdb

but when I boot from the backup disk, I got a error message check filesystem failed!

I do not know how to settle this problem. I thought the sdb is a copy of sda, so it can be booted. Then why it turns out this error message?

Maybe sdb is smaller? blockdev --getsz /dev/sda /dev/sdb Or volumes get mounted via /dev/disk/by-id/ which cannot work any more as the disk ID has changed. — Hauke Laging, Mar 04 '13 at 02:35
I can sure that the two disk space are same. /dev/sdb is a new fresh disk. Does it matter with gvfs ? — user1070948, Mar 04 '13 at 03:05
What is the fstab entry for the volume with the failing fsck? — Hauke Laging, Mar 04 '13 at 03:12
i boot the backup disk on another linux box, and then type fdisk -l i found this /dev/sdb1 ... Partion 1 does not start on physical sector boundary. — user1070948, Mar 04 '13 at 03:50
What is the output of sfdisk --unit S -l /dev/sda /dev/sdb? — Hauke Laging, Mar 04 '13 at 13:51

score 0 · Answer 1 · answered Mar 04 '13 at 06:53

0

Partion 1 does not start on physical sector boundary.

Sounds like something that could potentially be fixed by directly editing the partition table. I'm know quite sure how to do than with Linux but should give you a good starting point.

answered Mar 04 '13 at 06:53

LordOfTheRats

103

yes, i found that 'dd' doesn't copy superblock. I fixed this problem by two steps. 1) #fdisk /dev/sdb 2) w – user1070948 Mar 04 '13 at 07:48
I don't know why dd don't copy superblock even i use #dd if=/dev/sda of=/dev/sdb, If dd is byte-copy, why does it ingore superblock? – user1070948 Mar 04 '13 at 07:50

Kwakou · Answer 2 · 2016-06-02T08:55:23.510

0

can you compare with fdisk or sfdisk the partition tables of the two disks. In case of any mismatch : try to restore the original partition table : 1) sfdisk -d /dev/sda >/root/partition.img 2) sfdisk /dev/sdb

edited Jun 02 '16 at 08:55

answered Jun 02 '16 at 08:29

Kwakou

21

how to boot from a backup disk created by dd

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