I have an image of the entire disk created using dd. The disk structure follows:

kent@cow:~$ sudo fdisk -l

Disk /dev/sda: 750.1 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x000b8508

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           5       90872   729929303+  83  Linux
/dev/sda2           90873       91201     2642692+   5  Extended
/dev/sda5           90873       91201     2642661   82  Linux swap / Solaris

The image was created using:

dd if=/dev/sda of=image750.img

How would I, if it is possible, mount /dev/sda1 from the image so that I'm able to read the contents?

It's not an option to clone the HDD again, I know how to do it if I had only cloned the single partition by itself. I hope it's still possible with the current image.

Nowadays, there is a better way, no need to use offsets or kpartx anymore:

losetup --partscan --find --show disk.img

mount /dev/loop0p1 /mnt

to free up loop0, use after umount:

losetup -d /dev/loop0
  • 8
    On my Ubuntu 14.04 installation, losetup doesn't provide a --partscan option. – Cutter Oct 5 '14 at 23:11
  • 1
    @Cutter it was added in util-linux 2.21, Ubuntu 16.04. :-) – Ciro Santilli 新疆改造中心 六四事件 法轮功 Sep 24 '16 at 10:57
  • Having used kpartx first, which mounts the partitions like /dev/mapper/loop3p1, I just want to point out that losetup creates the devices like /dev/loop0p1. The answer notes that, but I read over it probably 10 times. :/ – Randy Syring May 4 at 21:46

I ran into this problem today and wanted to update the answers just as a reminder for myself. Instead of calculating the offset on your own, you can use a tool that provides you with mountable devices from a dd image: kpartx

http://robert.penz.name/73/kpartx-a-tool-for-mounting-partitions-within-an-image-file/

http://linux.die.net/man/8/kpartx

In the given case, it would need something like

sudo kpartx -a image750.img
sudo mount /dev/mapper/loop1p1 /mount/point -o loop,ro

where loop1p1 stands for the first partition, loop1p2 for the second, etc.

You've got the first part: fdisk -l to find the start offset. Take that number, multiply by 512, and you'll get the offset option to mount. So, for sda1 in your case, 5 * 512 = 2560. Then run the mount:

mount -o loop,offset=2560 -t auto /path/to/image.dd /mount/point

Loopmounting is only part of the answer.

Look at http://wiki.edseek.com/guide:mount_loopback#accessing_specific_partitions_in_the_image for help on specifying the partition. I think mount -o loop,offset=32256 /path/to/image750.img /mnt will work for you. but you really should read the mentioned tutorial.

  • the offset looks wrong; that corresponds to a partition start of 63 (<i>63 * 512 = 32256</i>). the offset in baumgart's answer looks more correct for this situation. the link is a good reference, but it'd be a better answer if you took the time to summarize the steps or commands needed for this procedure. thanks! – quack quixote Mar 7 '10 at 15:57

losetup -P automation

Method mentioned by https://superuser.com/a/684707/128124 (added in util-linux v2.21, added Ubuntu 16.04) , here are functions to automate it further. Usage:

$ los my.img
/dev/loop0
/mnt/loop0p1
/mnt/loop0p2

$ ls /mnt/loop0p1
/whatever
/files
/youhave
/there

$ sudo losetup -l
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE                                                                                      DIO
/dev/loop1         0      0         0  0 /full/path/to/my.img

$ # Cleanup.
$ losd 0
$ ls /mnt/loop0p1
$ ls /dev | grep loop0
loop0

Source:

los() (
  img="$1"
  dev="$(sudo losetup --show -f -P "$img")"
  echo "$dev"
  for part in "$dev"?*; do
    if [ "$part" = "${dev}p*" ]; then
      part="${dev}"
    fi
    dst="/mnt/$(basename "$part")"
    echo "$dst"
    sudo mkdir -p "$dst"
    sudo mount "$part" "$dst"
  done
)
losd() (
  dev="/dev/loop$1"
  for part in "$dev"?*; do
    if [ "$part" = "${dev}p*" ]; then
      part="${dev}"
    fi
    dst="/mnt/$(basename "$part")"
    sudo umount "$dst"
  done
  sudo losetup -d "$dev"
)

loop module max_part config

Decent method before util-linux v2.21.

loop is a kernel module, built into the kernel in Ubuntu 14.04.

If you configure it right, Linux automatically splits up the devices for you.

cat /sys/module/loop/parameters/max_part

says how many partitions loop devices can generate.

It is 0 by default on Ubuntu 14.04 which is why no auto-splitting happens.

To change it, we can either add:

options loop max_part=31

to a file in /etc/modprobe, or:

GRUB_CMDLINE_LINUX="loop.max_part=31"

to /etc/default/grub and then sudo update-grub.

How to set a module parameter is also covered at: https://askubuntu.com/questions/51226/how-to-add-kernel-module-parameters

After a reboot, when you do:

sudo losetup -f --show my.img

it mounts the image to a /dev/loopX device, and automatically mounts the partitions to /dev/loopXpY devices.

So this is the most convenient method if you are willing to reboot.

See also

If you have User mode files system like fuse, then in desktop environments likes Gnome and have installed tool like gnome-disk-image-mounter, then it without even root by right click and open with it.

I believe loopmounting is the answer -

sudo mkdir /path/to/dir/
mount -o loop example.img /path/to/dir/

The above should mount it under that directory.

This should unmount it:

umount /path/to/dir

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