Create, Mount and Restore partclone Images
Motivation: Space efficient binary backups of Raspberry Pi SD-cards
- Create a binary image of a ext4 partition
- The image should be small (e.g. 2GB/32GB occupied -> image size ~2GB)
- The backup process should not require more storage than the image itself (at no point in the backup process)
- The files inside the backup shall be accessible in a simple manner (for copying individual files)
- (optional) It should be possible to restore the image to the partition which is smaller than the original partition
- partclone (pacman): for backup and restore
- partclone-utils (AUR): for mounting the image for reading files
Plugin the device containing the partition to be backed up (e.g.
Optional: Backup the MBR + partition table
sudo dd if=/dev/sdx bs=512 count=1 > ./mbr.img
Optional: Save partition layout
sudo sfdisk -d /dev/sdx > ./partition-table.txt
Optional: Partclone image backup of boot partition
sudo partclone.fat32 --clone --source /dev/sdx1 --output - > ./boot.pcl
Partclone image backup of root ext4 partition
sudo partclone.ext4 --clone --source /dev/sdx2 --output ./rootfs.pcl
Optional: Restore the MBR + partition table
sudo dd if=./mbr.img bs=512 count=1 of=/dev/sdx # if restoring to a smaller disk, fix partition size: sudo cfdisk
Optional: Restore partclone image of boot partition
sudo partclone.fat32 --restore --source ./boot.pcl --output /dev/sdx1
Restore partclone image of root ext4 partition.
-C flag to disable the disk size check to enable restoring to smaller partitions (untested, but it should work).
sudo partclone.ext4 --restore --source ./rootfs.pcl --output /dev/sdx2 -C
Mounting a partclone Image
imagemount binary in the
partclone-utils uses the network block devices API to provide access to the backups through a standard filesystem interface.
This is done transparently, no further nbd utilities are required.
First we load the network block devices driver to create the devices
/dev/nbd1, …, which
imagemount needs in order to mount the backup.
sudo modprobe nbd
Next, mount the actual image.
sudo imagemount\ -v 3\ # verbosity level 3 -d /dev/nbd0\ # use the first network block device -f ./rootfs.pcl\ # our backup image -t ext4\ # our image contains a ext4 filesystem -m /media/imagemount\ # mount it here -D\ # do not daemonize, keep in foreground -r # mount read only (write does not work anyways)
Now the filesystem contained in the backup should be accessible at the specified mountpoint as long as the
imagemount process is active.
To unmount the filesystem, simply terminate the process.