Re: [Bug-ddrescue] How to restore just a single partition of a multi-partition image file?

[Antonio Diaz Diaz]

Subject: Re: Bug-ddrescue Digest, Vol 151, Issue 8
From: "Joe Kickman" <address@hidden>
Date: Tue, 22 Jan 2019 17:36:44 +0300
To: <address@hidden>

Hello, Shahrukh Merchant!
There really IS a simple way to write a single partition from a whole 
drive image to the place you want using ddrescue.
First, look at the partition table of the image and that of the drive 
that has enough space to fit the needed partition.
On Unix-like systems use something like this:
sudo fdisk /path/fulldrive.img
It'll show the partitions, their starting sectors and their length. 
Usually, C: starts in sectors 63, 2048 or 206848. Let's assume it starts 
at sector 206848 and is 400000000 sectors long.
Then do the same with your drive:
sudo fdisk /dev/sda
You will see the last sector occupied by existing partitions. For 
example, it is 2419999999 (1.21 Tb used).
So, from the sector 2420000000 the drive space is not used by partitions.
You'd better add 2048 sectors to that value and then write there 
(starting from sector 2420002048) your partition using something like this:
sudo ddrescue /path/fulldrive.img /dev/sda ~/200g-copy --ask -f 
-i206848s -s400000000s -o2420002048s
-o means the offset in the output file, here it is 2420002048 sectors.
-s is the size of the partition you are cloning, here it is 400 million 
sectors.
-i is the offset in the input file (your full drive image), 206848 sectors.

There is also another way, more safe.
Create an empty/raw partition on the free space of your disk. You may 
use fdisk etc. Its size must be (better) equal to or (safe, but not 
recommended) greater than the size of needed partition in the 
disk-image-file. List the partition table again using fdisk:
sudo fdisk /dev/sda
and remember the partition name (let's assume it is /dev/sda7)
Then use ddrescue:
sudo ddrescue /path/fulldrive.img /dev/sda7 ~/200g-copy --ask -f 
-i206848s -s400000000s

Also you can somehow mount a whole drive image without mounting its 
partitions. Then use something like this (I've never done that, so I am 
not sure about the syntax of the name of the partitions in the case you 
mounted fulldrive.img as a loop device. Maybe someone else or Google can 
help you. Here I assumed /dev/loop1 to be your mounted fulldrive image, 
its partition table is MBR, not GPT. And /dev/loop1p2 to be its second 
partition):
sudo ddrescue /dev/loop1p2 /dev/sda7 ~/200g-copy --ask -f

There is also a non-GNU way, using proprietary, but free for personal 
use program, DMDE. It is a disk editing and partition manipulting 
program with simple GUI, that has a feature to copy any range of sectors 
from images or devices to other or even the same images or devices. 
Also, it can help you to reconfigure your partition table, convert MBR 
to GPT and vice versa, etc. Free version is not very friendly to copy 
from damaged sources, so I use ddrescue to make clones or images; and 
DMDE to manipulate partition tables, bootsectors, FAT or MFT records, etc.