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I wanted to back my current state as an image but Im running into a problem: it seems that my microSD contains two partition: pi_root and pi_boot. How do I create an exact image of my microSD card with two parititons using dd?

Peter P
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    I'm not listing this as an answer as you requested dd but I'd encourage a look at Clonezilla (http://clonezilla.org) – Mark Nov 11 '17 at 15:17
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    I would also recommend Clonezilla. It is much safer and also faster than dd, See this description, https://askubuntu.com/questions/958242/fastest-way-to-copy-hdd/958248#958248; Notice that it works with any kind of mass storage device: memory card, USB pendrive, SSD, HDD. I suggest that you create an image of the whole drive with the bootloader and all the partitions (a compressed image, which is a directory with a number of files). -- When you restore from the image, you need a target drive of at least the same size as the source drive (not one byte smaller). The same is true for dd. – sudodus Nov 11 '17 at 17:01

2 Answers2

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You can use dd.

First you have to find the device name of the memory card, as this may depend on the card reader used. Run sudo lsblk The output will be something like this:

$ sudo lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
mmcblk0     179:0    0  29.3G  0 disk 
├─mmcblk0p1 179:1    0    56M  0 part /boot
└─mmcblk0p2 179:2    0  29.2G  0 part /

In this case, mmcblk0 is the only device, as it is done on a Pi. mmcblk0 is typically the name used with memory card readers, but USB card readers may also show up as sdb and so on.

To make a complete backup of the whole card, issue the command sudo dd if=/dev/mmcblk0 of=filename.img. If the device of the card is not mmcblk0, replace as per output of lsblk output.

This will read all of the memory card into the file filename.img. This should generally not be done from the Pi - as reading a live filesystem may lead to inconsistent results. Power off your Pi, and put the card into a different computer. Do not mount it.

To write the backup back to a card, reverse the input and outputs, i.e. sudo if=filename.img of=/dev/mmcblk0.

Please be very careful, and read dd commands three times before you execute it. If you mix up input and output for instance, you risk destroying all your data!

If you want to compress the image for storage, run for instance bzip2 filename.img. This will reduce the file size significantly, especially if you have a lot of free space. To decompress the image, for restoring, run bunzip2 filename.img.gz.

vidarlo
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If you insist on using dd you can do it like described below. Just a word of warning beforehand, there are simpler to use tools like clonezilla which are less error prone and probably far more performant as using dd.

First make sure you know the drive letters for your SD card (I assume here it is /dev/sdb1 and /dev/sdb2 containing your partitions). You can simply pull a full image of this drive by not addressing the single partitions instead using the drive itself (i.e. /dev/sdb). To fetch the full contents of that drive in an image do:

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

to reverse it:

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

You may ask how you can get the proper drive letters to use, this you can by using lsblk which will produce an output similar to this:

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
fd0      2:0    1     4K  0 disk 
sda      8:0    0 119,2G  0 disk 
├─sda2   8:2    0    16G  0 part [SWAP]
└─sda3   8:3    0 103,2G  0 part /
sdb      8:16   0   1,8T  0 disk 
├─sdb1   8:17   0     1G  0 part /media/<username>/pi_boot
└─sdb2   8:18   0    15G  0 part /media/<username>/pi_root
Videonauth
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