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SD-card backup and restore guide.md

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Backups are currently stored as raw disk images inside compressed SquashFS-containers uploaded to Google Drive.

Figure out what devcie the the SD card has in your system

  1. Insert SD card in card reader and make sure you know its device name

    • NOTE: If you use the wrong devicename below you might try to overwrite the harddrive in your workstation so be careful and check the devicename!
    # lsblk
# dmesg | tail -n 50
    • Below, instead of sdx, use the real devicename you got in the previous step

Backing up SD cards using a workstation

  1. Create a directory where you would like to save your image (which will be included in the compressed archive in a later step)

    $ mkdir sdcard-backup
$ cd sdcard-backup

  2. Dump the whole SD card to a file together with SHA-256 integrity checksum using pv and tee

    (If you need to install the commands on your workstation, use sudo pacman -S pv tee)

    # pv /dev/sdx | tee sdcard.dd | sha256sum > sdcard.dd.sha256
# sed -i 's/-$/sdcard.dd/' sdcard.dd.sha256

    OR

    • If you can not install pv and tee the same result can be acheived using dd but without any indication of progress)

      # dd if=/dev/sdx of=sdcard.dd
# sha256sum sdcard.dd > sdcard.dd.sha256

    You can include other data besides the image in the backup archive by adding files in this directory, they will then be included in the archive. For example fdisk -l /dev/sdx > fdisk-l.txt or you could edit a note in a textfile.

  3. Compress the archive

    1. Exit the working directory where the raw backup output resides

      # cd ..

    2. Compress the whole directory along with content created in previous steps

      This will create a mountable SquashFS-container (mksquashfs can be installed on Arch Linux workstations using pacman -S squashfs-tools)

      # mksquashfs sdcard-backup sdcard-backup-$(date +%F).sqf -comp xz

      OR

      • create a bzip2-compressed tar-file
      # tar cvjf sdcard-backup-$(date +%F).tar.bz2 sdcard-backup

  4. Clean up by deleting the backup directory

    # rm -rf sdcard-backup

Cloning a previously made backup to SD cards using a workstation

  1. Create a mountpoint for accessing the contents of the backup archive and mount the SquashFS-archive

    $ mkdir backupmnt

  2. Mount archive contents in the directory, enter directory and list contents

    # mount sdcard-backup-1234-56-78.sqf backupmnt
# cd backupmnt
# ls -lah

  3. Clone the raw dd-image from the archive to the physcial SD card using pv (pipeviewer)

    # pv sdcard.dd > /dev/sdx

  4. Sync and eject SD card to ensure everything is written to it before removal

    # sync
# eject /dev/sdx

  5. Clean up

    # cd ..
# umount backupmount
# rmdir backupmount