dd image too large to recover

Question

I made an image with dd

sudo dd if=/dev/sda of=/path_to_external_drive/backup.img

Now I wanted to recover the system after the mount of all partitions went smoothly. When I make

sudo dd if=backup.img of=/dev/sda

I don't get any error messages until I try to boot the system.

I get the following error message from sudo fdisk -l because I wanted to see why the BIOS does not found any partition.

Partition 1 does not start on physical sector boundary

So I tried Disk Image Writer from my live stick but it says, that the image is 41 kB too large.

How can this happen and how can I fix it? Is there another way, besides buying a new SSD, to restore the system?

fdisk -l backup.img:

fdisk -l /dev/sda:

GPT PMBR size mismatch (976773247 != 976773167) will be corrected by w(rite).

Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x635f93a2

Device     Boot Start       End   Sectors   Size Id Type
/dev/sda1           1 976773247 976773247 465.8G ee GPT

Partition 1 does not start on physical sector boundary.

gdisk -l /dev/sda:

GPT fdisk (gdisk) version 1.0.1

Warning! Disk size is smaller than the main header indicates! Loading
secondary header from the last sector of the disk! You should use 'v' to
verify disk integrity, and perhaps options on the experts' menu to repair
the disk.
Caution: invalid backup GPT header, but valid main header; regenerating
backup header from main header.

Warning! One or more CRCs don't match. You should repair the disk!

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: damaged

****************************************************************************
Caution: Found protective or hybrid MBR and corrupt GPT. Using GPT, but disk
verification and recovery are STRONGLY recommended.
****************************************************************************

Disk /dev/sda: 976773168 sectors, 465.8 GiB  
Logical sector size: 512 bytes  
Disk identifier (GUID): 8DC2A4AA-C369-4ED8-B876-DCE0418A1BD0  
Partition table holds up to 128 entries  
First usable sector is 34, last usable sector is 976773214  
Partitions will be aligned on 2048-sector boundaries

Total free space is 4157 sectors (2.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name  
   1            2048          923647   450.0 MiB   2700  Basic data partition  
   2          923648         1128447   100.0 MiB   EF00  EFI system partition  
   3         1128448         1161215   16.0 MiB    0C01  Microsoft reserved ...  
   4         1161216       669571071   318.7 GiB   0700  Basic data partition  
   5       669571072       960290815   138.6 GiB   8300  
   6       960290816       976771071   7.9 GiB     8200  

Answer 1

Your image file is 40KB larger than the disk (976773248 - 976773168 sectors). It can't work to dd the whole image to the disk. I guess your dd command was showing some warnings like "no space left" or something.

But you have luck. The last (6th) partition is just a swap partition. You could use gdisk and mkswap to resize the last partition and to correct the partition table:

$ gdisk /dev/sda

1. remove the last partition
2. repair the gpt partition table (should be done automatically)
3. re-create the last partition (will be a bit smaller than before)

Then format the new swap partition:

$ mkswap /dev/sda6

Notes regarding interactive gdisk usage:

I cannot really predict what gdisk /dev/sda will show you. Type "h" for help. Type "d" and then "6" to remove last partition. "n" and "6" to re-create last partition. Exit and write your changes with "w". gdisk does not write anything unless you exit with "w". If unsure you can always exit/cancel by "q" or "ctrl-c".