How to backup a Raspberry Pi and restore it on a smaller SD card

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 :

  1. when you copy the whole disk, the image is as big as the disk, even if the is lots of empty space on it.
  2. 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.

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How to make a RPi boot silent

Here are few modification that allow a very quiet boot, nothing will appear on the screen before the login prompt.
Thus if you start a visual application before that (in /etc/init.d for example) you will not see anything on the screen before your application starts.

First modify the /boot/cmdline.txt like this :
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty3 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=noop rootwait loglevel=3 logo.nologo vt.global_cursor_default=0

here are the details of the changes :
console=tty3 redirect all the post messages to the third console (hit CTRL + ALT + 3 to see them after boot).
loglevel=3 make it less verbose, only errors are reported
logo.nologo disable the RaspberryPi logo on boot
vt.global_cursor_default=0 Disable the blinking cursor.

Moreover you can add disable_splash=1 to /boot/config.txt in order to disable the rainbow splash on power on.

At the en, vous can completly disable the prompt #1 by editing the file /etc/inittab and commenting the following line :
1:2345:respawn:/sbin/getty --noclear 38400 tty1

That’s all !