Backup (or Clone) a Raspberry Pi SD Card 8

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8 thoughts on “Backup (or Clone) a Raspberry Pi SD Card”

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  abracadabricx May 23, 2016 at 12:29 pm

  Hi, I recognise your story, I have a few of those projects….. To alleviate the two disadvantages of your second approach I wrote a rudimentary bash script. The approach is to take the sd card from the PI and slot it in some linux computer that you use to make a backup. The script measures and calculate a minimum image size, shrinks the filesystem and subsequently the partition on the sd card, which is quite fast. After that it writes an image of only those blocks that are part of the resized partitions to a location of choice. It works well, and all images made have been succesfully tested. You’re welcome to use or share it, and I’ll be happy to learn how it could be improved. Let me know what you think.

  #!/bin/bash -e
  #######!/bin/bash -ex # The x is to be used for debugging.

  #——————————————————————————
  #
  # 9 may 2016, backuPi.sh
  #
  #
  # Calculates the minimum size of the sd card, and then resizes filesystem
  # and partition.
  # Subsequently creates an image of the relevant partitions space.
  #
  #
  #
  #——————————————————————————

  function calcMiB()
  {
  # Calculate size in MiB, for easier reading.
  local partsizeblocks=$1
  local KBperblock=$2
  local partsizeKiB=$(( ${partsizeblocks} * ${KBperblock} ))
  local quotientMiB=”$(( (${partsizeblocks} * ${KBperblock}) / 1024 ))”
  local modulusMiB=$(( ($partsizeKiB – ($quotientMiB * 1024))*1000/1024))
  local modulusMiB2=”$(( (${partsizeblocks} % ${KBperblock}) / 1024))”
  echo “${quotientMiB},${modulusMiB} MiB.”
  }

  # check which drive is the sd card:
  echo “Please select the drive you want to format and write an image to.”
  echo “The following filesystems have been found:”
  lsblk
  read -e -p “Which blockdevice: ” -i “sdc” myblkdev
  read -e -p “Which partition do you want to shrink: ” -i “2” targetpartnr
  targetpart=”${myblkdev}${targetpartnr}”

  # Unmount directories, otherwise online shrinking from resize2fs would be
  # required but this throws an error.
  if grep -s “${myblkdev}” /proc/mounts
  then
  echo “Start unmounting partitions”
  sudo umount -v “/dev/${myblkdev}”? # Questionmark is wildcard.
  fi

  # Check the filesystem/partition.
  sudo e2fsck -fy “/dev/${targetpart}”

  myblockcount=$(sudo tune2fs -l “/dev/${targetpart}” | grep ‘Block count’ | awk ‘{print $3}’)
  myfreeblocks=$(sudo tune2fs -l “/dev/${targetpart}” | grep ‘Free blocks’ | awk ‘{print $3}’)
  myblocksize=$(sudo tune2fs -l “/dev/${targetpart}” | grep ‘Block size’ | awk ‘{print $3}’)
  mysectorsize=$(sudo sfdisk -l “/dev/${myblkdev}” | grep Units | awk ‘{print $8}’)
  mystartsector=$(sudo fdisk -l “/dev/${myblkdev}” | grep “${targetpart}” | awk ‘{print $2}’)

  # Calculate the smallest partition size, in blocks.
  myusedblocks=$(( $myblockcount – $myfreeblocks ))
  # Calculate target partion size, adding a bit of margin, about 8%.
  mytargetblocks=$(( $myusedblocks + ($myusedblocks * 2 / 25) ))

  # Calculate KiB per block to aid further calculation in KiB’s:
  if (( “${myblocksize}” >= “1024” ))
  then
  KBperblock=$(( $myblocksize/1024 ))
  else
  echo “Blocksize is awkward: ${myblocksize}. Not sure what to do, stopping.”
  exit
  fi

  # Round up new part size to multiple of blocksize to facilitate creation.
  mynewpartsize=$(( (($mytargetblocks + $KBperblock-1) / $KBperblock) * $KBperblock ))

  # Calculate and print the existing data and target partition size.
  echo “”
  echo “The size of the data on partion /dev/${targetpart} is \
  $( calcMiB ${myusedblocks} ${KBperblock} )”
  echo “”
  echo “The new size of the data on partion /dev/${targetpart} will be \
  $( calcMiB ${mytargetblocks} ${KBperblock} )”
  echo “”

  # Calculate multiplier from sector size to block size
  sectorsperblock=$(( $myblocksize/$mysectorsize ))
  # Calculate end point in sectors, that is what fdisk requires.
  mynewendpoint=$(( $mystartsector + ($mynewpartsize * $sectorsperblock) ))

  # Start execution:
  # Resize the filesystem, values in 1024 bytes, see the “K” at the end.
  # Example, if blocksize was 4096, nr of blocks x 4 is the resize value.
  sudo resize2fs -fp “/dev/${targetpart}” $(( $mynewpartsize * $KBperblock ))K
  # Resize partion, to make matters complicated values are in sector sizes.
  # NB, the -s switch does not work, putting Yes after the command is the work around.
  sudo parted “/dev/${myblkdev}” unit s resizepart “${targetpartnr}” “${mynewendpoint}” yes
  sync

  # Mounting the drives does not work: error looking up object with path ….
  #udisksctl mount -p block_devices/sdc1
  #udisksctl mount -p block_devices/sdc2
  #udisksctl mount -b /dev/sdc1
  #udisksctl mount -b /dev/sdc2

  # Backup resized image
  read -e -p “Backup the resized image? [Y/N] ” -i “Y” backupchoice

  if [[ “${backupchoice}” =~ ^([yY][eE][sS]|[yY])$ ]]
  then
  mkdir -p ~/backups
  read -e -p “Filename :” -i “$(date +%g%m%d)-raspbianbackup.img” Pibackupname
  sudo dd if=”/dev/${myblkdev}” | pv | sudo dd of=~/backups/”${Pibackupname}” bs=512 count=”${mynewendpoint}”
  echo “Backup succesfull.”
  fi
  exit

  • 

    Reply ↓

    bobby Post author May 23, 2016 at 6:36 pm

    Wow, great work! I have yet to test it, but I’ll be sure to do so soon. Thanks for your contribution, it’s much appreciated.

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    Reply ↓

    Anton August 9, 2016 at 1:48 am

    Hi abracadabricx,

    Thanks for sharing this. I’m a noob to linux and I’m not quite sure how to use this script. I tried to typing the commands one after other and it didn’t work. Highly appreciated if you can explain how can I use your script. Thanks!

    Cheers,
    Anton

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    Reply ↓

    Anton August 9, 2016 at 6:51 am

    Hi abracadabricx,

    Can you please explain how can I use your script ? I’m quite new to Linux and Raspberry Pi world. Appreciated if you can advise how can I execute your script. Many Thanks!

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      Reply ↓

      Sisir July 4, 2017 at 7:09 am

      The latest version of Raspberry pi OS has a built in software that is very simple to use. It does a exact copy of the SD card. You need a USB card reader with a new empty SD card. Plug this into the usb port of Raspberry pi. And then copy using the software to make copy of the SD card you are booting from …

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  Reply ↓

  Chuck Davis June 17, 2016 at 2:56 pm

  Can an SD card be programmed to cause a Raspberry Pi/Retropi to boot up and be an Amiga 1200/030, only, to the user?

  • 

    Reply ↓

    bobby Post author June 17, 2016 at 6:56 pm

    Hi Chuck,
    Thank you for visiting my site. In regards to your question, I really can’t say. It’s not something I tried.
    Sorry.

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  Reply ↓

  Mark McCurry April 28, 2021 at 8:47 am

  God Bless You!!!! I have been working for over a week to shrink a 64 GB image to a 32 GB card for our big Pi rollout because we found cheaper Pi kits but they used 32 GB cards. I had put a great deal of effort in this image with overlayfs and other optimizations, and to be honest there was no way I was going to remember every optimization I had done to achieve perfection in this 64 GB card. I had given up hope and ordered a lot of 64 GB cards to switch out, but I then stumbled on your page and Option #3 worked perfectly! None of the other options I had tried up until this point worked I suppose because of the overlayfs and other changes that we made to boot.

  I know this is an old post, but I just wanted to let you know that your post is still making a difference well into 2021! Thanks again!