blog/content/posts/2015/02/14/backing-restoring-whole-block-devices.md

title	date	tags
Backing up and restoring whole block devices	2015-02-14 08:30:51	raspberry pi hardware

SD cards are not really a reliable storage, especially when used constantly e.g. while sitting in always powered-on Raspberry Pi. Because of that I've recently needed to perform lots of backup/restore operations ;) I wrote this script for backing up:

#!/bin/bash

if [[ -z $1 ]]; then
    echo "usage: $0 device_to_clone"
    exit
fi

device=$1

timestamp=`date +%Y%m%d`
dest_file="/tmp/$timestamp.dd.xz"

echo "about to clone $device to $dest_file"
echo "ctrl-c or [enter]"
read

sudo umount $device?
sudo umount $device

sudo sync
sudo pv -tpreb $device | dd bs=4M | pixz > $dest_file
sudo sync

And this one for restoring:

#!/bin/bash

if [[ -z $1 ]] || [[ -z $2 ]]; then
    echo "usage: $0 restore_file.xz device_to_restore_to"
    exit
fi

source_file=$1
if [[ ! -f $source_file ]]; then
    echo "cannot open $source_file"
    exit
fi

device=$2

echo "about to restore $source_file onto $device"
echo "ctrl-c or [enter]"
read

sudo umount $device?
sudo umount $device

pv -tpreb $source_file | pixz -d | sudo dd bs=4M of=$device
sudo sync
sudo eject $device

Some of the more fun features include progressbars and making sure you've unmounted the device properly before ;) This also uses parallel threads to deflate the data, so the XZ compression should not be a bottleneck on any modern machine. The scripts above were used to backup and restore SD cards but will work for any block device, be it an external or internal disk drive, etc. usage example [remember to use the whole device, not just its partition as an argument]:

./backup_sdcard /dev/sdc
about to clone /dev/sdc to /tmp/20150214.dd.xz
ctrl-c or [enter]

[sudo] password for cyryl:
umount: /dev/sdc1: not mounted
umount: /dev/sdc2: not mounted
umount: /dev/sdc: not mounted
19,6MiB 0:00:02 [9,72MiB/s] [>                       ]  0% ETA 0:52:26