Woozle: Accessing a disk image in Linux moved to accessing a disk image in Linux

2006-05-25T13:43:00Z

Accessing a disk image in Linux moved to accessing a disk image in Linux

← Older revision	Revision as of 13:43, 25 May 2006
(No difference)

Woozle: moved from Qemu on Linux

2006-02-22T02:08:22Z

moved from Qemu on Linux

New page

[[Computing]]: [[Software]]: [[Linux]]: [[{{PAGENAME}}|accessing a disk image]]
==Instructions==
In general, assuming the image file was made with the default disk head/sector parameters using [[qemu-img]] (in [[qemu]]) or [[bximage]] (in [[bochs]]):
[[sudo]] [[mount]] -o loop,offset=32256 <u>/path/to/image</u> <u>/path/to/directory/</u>
Specific example ({{Woozle}}'s system):
[[sudo]] [[mount]] -o loop,offset=32256 /home/woozle/win98/c.img /mnt/qemu
The reason for the offset is that the image represents an entire ''disk''; you can only mount a ''partition'', not the entire disk. The offset is where the main partition starts. You can find out where partitions are in a disk image by using fdisk:
[[fdisk]] /path/to/image
Woozle example:
[[fdisk]] /home/woozle/win98/c.img
This takes you to a menu, where you type "p" to get a partition table:
Command (m for help): p

Disk c.img: 0 MB, 0 bytes
64 heads, 63 sectors/track, 0 cylinders
Units = cylinders of 4032 * 512 = 2064384 bytes

Device Boot Start End Blocks Id System
c.img1 * 1 520 1048288+ c W95 FAT32 (LBA)

Based on what I worked out below (which you don't need to read unless that sort of thing interests you), you work this equation to find the correct offset:
[Start] x [bytes-per-sector] x [sectors/track]
...where [bytes-per-sector] is the number after the "*" in "cylinders of..."

(Working backwards from the knowledge that 32256 – which was a Magic Number found by Tenebram – is the correct number, and trying to figure out why it is correct: If we presume that "sectors/track" means the number of sectors per track for a ''single head'', then 4032 (which is 64 x 63) must be the number of sectors per track for ''all'' heads, and 512 is probably the sector size in bytes. The offset to a given sector, then (waving a magic wand at all this so that it matches reality somehow) is [start] x [bytes-per-sector] x [sectors-per-track] – which leads us to deduce that the units for the [start] number must be "tracks".)

accessing a disk image in Linux - Revision history

Woozle: Accessing a disk image in Linux moved to accessing a disk image in Linux

Woozle: moved from Qemu on Linux