If you’re using Raspberry Pi, you might know the famous command line utility dd, useful to write a Raspbian image to a blank SD card (cf. http://elinux.org/RPi_Easy_SD_Card_Setup).
You can also use this tool to do backup of the whole disk, but it has two drawbacks :
- when you copy the whole disk, the image is as big as the disk, even if the is lots of empty space on it.
- when you restore the backup you need a disk at least as big as the original one.
Those two disadvantages lead me to find a solution to make backups smaller and more versatile. The solution I’ll describe here is an adaptation of Ubuntu’s documentation : https://help.ubuntu.com/community/BackupYourSystem/TAR and have been tested on Ubutnu 14.04.
To backup, make a tarball of all the files on the partitions :
cd /path/to/sdcard/partition && sudo tar -cpzf /path/to/backup.tar.gz --one-file-system .
As there are 2 partitions on Raspberry Pi’s sdcard : the first is FAT32 and small (around 60MB) and the second is ext4
You should make two backups. Forme its :
cd /media/boot && sudo tar -cpzf /home/antoine/boot.tar.gz --one-file-system .
cd /media/system && sudo tar -cpzf /home/antoine/system.tar.gz --one-file-system .
My sdcard is 16Go while my backup is less than 600Mo !
To restore this backup on a new sdcard, you first have to format it. Make 2 partitions, first FAT32 and 60MB, the second ext4 and big enough to receive all the backup datas. Then extract the 2 archivess to the new 2 partitions with this command :
sudo tar -xvpzf /path/to/boot.tar.gz -C /path/to/sdcard/partition/boot/ --numeric-owner
That’s it !
One drawback is that method works only on system that can mount ext4 something that Windows and Mac OSX can’t do natively…