Ask Ubuntu is a question and answer site for Ubuntu users and developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am trying to clone an SD card which may contain a number of partitions, some of which Ubuntu cannot recognize. Generally, I want to clone the whole volume, not only some partition. So, I mount the SD card and see something like this in the Log viewer:

kernel: [  262.025221]  sdc: sdc1 sdc2

alex@u120432:~$ ls /dev/sdc*
/dev/sdc  /dev/sdc1  /dev/sdc2

Since I want to copy the whole disk, I execute:

dd if=/dev/sdc of=sdimage.img bs=4M

File sdimage.img, 7.9 GB (7,944,011,776 bytes) is created (SD card is 8 GB). Now I mount another SD card and execute:

dd if=sdimage.img of=/dev/sdc bs=4M

The problem is that the second dd command hangs on some stage, and never succeeds. After this, I cannot reboot or shut down computer, and I need just to switch power off.

Is this the correct approach? Maybe there is another way to clone an SD card?

OS: Ubuntu 12.04 (Precise Pangolin), 32 bit.

share|improve this question
Can you mount created img file and see if it is created correctly? – Milan Todorovic Dec 11 '12 at 14:40
@MilanTodorovic - how can I do this? – 0123456789 Dec 11 '12 at 15:15
If I remember correctly: mount -o loop sdimage.img /path/to/mount. Then check to see if you can browse img file correctly. – Milan Todorovic Dec 11 '12 at 15:17
@MilanTodorovic: I tried sudo mount -o sdimage.img /dev/mydisk and got: mount: can't find /dev/mydisk in /etc/fstab or /etc/mtab Possibly I need to create some dev entry before. Can you post this as answer with some details? Thanks. – 0123456789 Dec 11 '12 at 15:22
you should not be using dd on mounted devices. unmount all the partitions first, then your command should work. – ubfan1 Dec 11 '12 at 17:33
up vote 17 down vote accepted

You should not be using dd on mounted devices. unmount all the partitions first, then your command should work.

share|improve this answer
why is the opposite for me? I've Ubuntu 12.10 and the command has works only with partitions monted... – Luca Davanzo Feb 13 '14 at 10:12
@Velthune Are you sure about that? If so, I'd suggest making your own question. – Vreality Jul 17 '14 at 3:58

I am using dd tool to clone usb sticks with multiple partitions, here is my command:

sudo dd if=/dev/sdb of=/dev/sdc bs=4096 conv=notrunc,noerror

notrunc - do not truncate the output file
noerror - continue after read errors

share|improve this answer
Doesn't this require two SD card readers? – Peter Mortensen Mar 3 '15 at 20:27
@PeterMortensen yes it does, many of us use those 4-in-1 type adapters. – Teque5 Mar 15 at 21:37

dd is fine, but I prefer cat /dev/sdc/ > ~/backup.iso If you want to put it on an SD card again, just run cat ~/backup.iso > /dev/sdc

share|improve this answer
Both SD are 8 GB. cat can be used to make SD image, but to make another SD I should use dd, right? – 0123456789 Dec 11 '12 at 15:17

Insert the original sd card and check the name of the device (usually mmcblkX or sdcX):

sudo fdisk -l

In my case the sd card is /dev/mmsbkl0. Now you have to unmount the device:

sudo umount /dev/mmcblk0

Now to create an image of the device:

sudo dd if=/dev/mmcblk0 of=~/sd-card-copy.img

This will take a while.

Once it's finished, insert the empty sd card. If the device is different (USB or other type of sd card reader) verify its name and be sure to unmount it:

sudo fdisk -l
sudo umount /dev/mmcblk0

Write the image to the device:

sudo dd if=~/sd-card-copy.img of=/dev/mmcblk0

The write operation is much slower than before.

share|improve this answer

Here are the steps which worked for me on Ubuntu to restore the image file (~/raspberrypi2.img in my case) back to a new SD card (inspired heavily by Alon's reply above):

  1. Insert the micro SD card via the card reader.
  2. Open the Disks app.
  3. Quick format the whole card (not a specific partition).
  4. Close Disks.
  5. Open terminal and execute:

    sudo fdisk -l

Relevant output (which showed there were no partitions due to the quick format of the whole card):

Disk /dev/sdb: 7.4 GiB, 7948206080 bytes, 15523840 sectors 
Units: sectors of 1 * 512 = 512 bytes 
Sector size (logical/physical): 512 bytes / 512 bytes 
I/O size (minimum/optimal): 512 bytes / 512 bytes 
Disklabel type: dos 
Disk identifier: 0x6957f2f2

sudo dd if=~/raspberrypi2.img of=/dev/sdb

This step takes a few good minutes (even on USB3). Make sure to not interrupt it by any operation which will invoke mounting (opening the Files or Disks apps).

Thanks for everyone's answers.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.