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Old 01-21-2008, 07:54 AM
Remy Blank
 
Default "loopback mount" hard-drive image created with dd?

Yahya Mohammad wrote:

# losetup /dev/loop0 /path/to/diskimage
# fdisk -l /dev/loop0
(example)
Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sdb1 * 1 1044 8385898+ c W95 FAT32 (LBA)
/dev/sdb2 1045 19457 147902422+ 83 Linux


Thanks for the tip! I didn't know you could mount a whole disk image as
loopback, and see the partition table with fdisk. I always printed the
partition table before making the disk image.



I second that, I'm curious to know if it works


It does, I have done it before, but there's a special case for the first
partition of the disk. According to your output of fdisk, it is supposed
to start at cylinder 1. However, if you run fdisk with the -u option
(giving the positions and sizes in sectors), you get the following:


(example)
# fdisk -lu /dev/loop0

Disk /dev/loop0: 10.0 GB, 10056130560 bytes
240 heads, 63 sectors/track, 1299 cylinders, total 19640880 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0xc1afc1af

Device Boot Start End Blocks Id System
/dev/loop0p1 * 63 4097519 2048728+ b W95 FAT32
/dev/loop0p2 4097520 8195039 2048760 5 Extended
/dev/loop0p5 4097583 8195039 2048728+ b W95 FAT32

That is, the first partition starts at sector 63, i.e. at an offset
value of 63 * 512 = 32256.



oh, and make a backup just in case


And mount the filesystem read-only with the "ro" mount option.

-- Remy
 

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