Impossible to restore a backup raspberry 3 image

Question

The sdcard of my raspberry 3 crashed a few weeks ago. I am trying to restore the raspbian system on another sdcard of the same capacity using a backup image of the sdcard created before the crash.

Using a Lubuntu virtual box hosted on my windows 10 computer, I am entering this command line in the terminal

gunzip --stdout ./backup_file.gz | sudo dd bs=4M of=/dev/sdb

as propose the website enter link description here. sdb is the sdcard. The copy takes some time (~10h) but it is a 64GB sd card, so it's normal I think. The process is finishing without any error.

My problem is that when I insert the sdcard back in the raspberry pi and turn it on, nothing append : the two lights of the pi are turned on together, they are not blanking at all, and nothing append after. No signal is sent to the HDMI cable neither.

What I already tried without success :

• Taking an older backup file
• Taking another sd card
• Taking another raspberry pi 3

Do you have any idea of what is going on ? Thank you in advance for your help.

---

EDIT1 : for information, I have created the backup image of the raspberry pi 3 while it was still ok using this command line : sudo dd bs=4M if=/dev/mmcblk0 | gzip > /media/pi/USBkey/backup_file.gz

---

EDIT2 : After the restore operation, I can't visualize the result in gparted. I am getting this error : Invalid partition table on /dev/sdb -- wrong signature ffff.

---

EDIT3 : I think that there is a partition problem when copying the image on a new sdcard. Indeed, using sfdisk :

• Exploring the partitions of the backup image sudo sfdisk -l <PATH_TO_IMAGE> :

  Disque backup-20170201 : 58,2 GiB, 62537072640 octets, 122142720 secteurs
  Unités : sectors of 1 * 512 = 512 octets
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  Disklabel type: dos
  Disk identifier: 0xd94ffdb3
  
  Périphérique      Amorçage  Start       Fin  Secteurs  Size Id Type
  backup-20170201p1            2048    251953    249906  122M  e W95 FAT16         (LBA)
  backup-20170201p2          251954 122142719 121890766 58,1G  5 Étendue
  backup-20170201p5          253952    319485     65534   32M 83 Linux
  backup-20170201p6          319488    454655    135168   66M  c W95 FAT32 (LBA)
  backup-20170201p7          458752 122142719 121683968   58G 83 Linux
  

• Exploring the partitions of the sdcard sudo sfdisk -l <PATH_TO_SDCARD> :

  Ignoring extra data in partition table 5.
  Ignoring extra data in partition table 5.
  Ignoring extra data in partition table 5.
  Invalid flag 0xffff of EBR (for partition 5) will be corrected by w(rite).
  Disque /dev/sdb : 59,6 GiB, 64021856256 octets, 125042688 secteurs
  Unités : sectors of 1 * 512 = 512 octets
  Sector size (logical/physical): 512 bytes / 512 bytes
  I/O size (minimum/optimal): 512 bytes / 512 bytes
  Disklabel type: dos
  Disk identifier: 0xd94ffdb3
  
  Périphérique Amorçage      Start        Fin   Secteurs  Size Id Type
  /dev/sdb1                   2048     251953     249906  122M  e W95 FAT16 (LBA)
  /dev/sdb2                 251954  122142719  121890766 58,1G  5 Étendue
  /dev/sdb5             4295219249 8590186543 4294967295    2T ff BBT
  

How can I solve that ?

---

Answer 1

tryout win32 disk imager with windows system along with a card reader which read the sd card and stores to the addressed memory location. (https://sourceforge.net/projects/win32diskimager/)

1. Prepare the sd card using SD Card Formatter
2. Uncompress the image file *.gz
3. Write the image on the sdcard using Win32 Disk Imager

Answer 2

Try plugging your SD card in your Linux PC (or mount it if it's plugged already): you should be able to see the root partition contents. If you don't, there is a problem with your backup (a good practice would be to restore your system from a backup when you make one, then you know you really have a backup).

Another thing you should have though of when making your backup with

sudo dd bs=4M if=/dev/mmcblk0 | gzip > /media/pi/USBkey/backup_file.gz

is to remount your root read-only beforehand (did you?). If a write on /dev/mmcblk0 happens while your backup command is running, your backup may end up to be inconsistent. A safe and simple alternative is to backup your SD card using a PC.

Also, double-check that dd runs without errors, perhaps post a message you get at the end. No two SD cards have exactly the same size, and if your new card is a little bit smaller than the old one, you may be writing incomplete image on it, which will fail to mount.

Answer 3

The problem appears to be that you are gunzipping the contents of a disk (potentially only one) to a disk that may or may not have been formatted correctly.

When you use dd, you are duplicating the a disk, for example from loop device (a *.img file) to the block device /dev/diskX. The image in this case would define the disk geometry and dd would essentially create the partitions and lay the files down at the block level.

In your case, you may not have a gzip of the block devices, but the root filesystem instead. In this case, /dev/diskX must be partitioned to boot, root and swap and your tarball is likely root with boot mounted at /boot.

You need to check if the gzip contents are files that reside on a disk or a partitioned disk image itself. You can extract the contents to check.

If the contents are a root filesystem you may just need to format the SD card as boot root and swap. Then mount the root, on /mnt/root of your host, and mount the boot partition at /mnt/root/boot. Now extract your backup on the mounted and formatted SD card root partion with boot mounted at /boot (so your kernel and necessary boot files are places on that parition. Unmount /mnt/root/boot and /mnt/root and try to boot off the device again.

I recommend looking up the proper partitioning of the SD card for the RPi first, IIRC the boot device will be FAT32 and the root device will need to be EXT4 or another journaled (or non-journaled) filesystem