loopback magic

First you used dd to grab the entire contents of a disk. Now you want to copy that disk to another one. Only the new disk isn't the exact same size as the old one, and probably doesn't have the same geometery. In which case you would be better off doing an rsync then dd to the new disk. The following trick will also work if you just want to read a partition.

First we need the offset of each partition:

#sfdisk -uB -l fulldump

last_lba(): I don't know how to handle files with mode 81a4

Disk fulldump: cannot get geometry



Disk fulldump: 17 cylinders, 255 heads, 63 sectors/track

Warning: The partition table looks like it was made

  for C/H/S=*/224/56 (instead of 17/255/63).

For this listing I'll assume that geometry.

Units = blocks of 1024 bytes, counting from 0



   Device Boot   Start       End    #blocks   Id  System

fulldump1           28    144255     144228   83  Linux

fulldump2       144256  39080831   38936576   8e  Linux LVM

fulldump3            0         -          0    0  Empty

fulldump4            0         -          0    0  Empty

We ignore the warning messages, because we see that the first partition starts at 28*1024=28672 bytes. So we can mount that easily.

# mount -o loop,offset=$((28*1024)) fulldump /mnt

# ls /mnt

config-2.6.18-164.el5                message

config-2.6.18-194.11.3.el5           symvers-2.6.18-164.el5.gz

grub/                                symvers-2.6.18-194.11.3.el5.gz

initrd-2.6.18-164.el5.img            System.map-2.6.18-164.el5

initrd-2.6.18-194.11.3.el5.img       System.map-2.6.18-194.11.3.el5

initrd-2.6.18-194.11.3.el5-PG1.img   t/

initrd-2.6.18-194.11.3.el5-PG2.img   vmlinuz-2.6.18-164.el5

initrd-2.6.18-194.11.3.el5-SSD1.img  vmlinuz-2.6.18-194.11.3.el5

lost+found/

I used $((28*1024)) because this way bash does the calculation for us.