Mount individual partitions from a disk image
Say you’ve made an image of a partition. You might know that you can use mount -o loop to mount the image. But what do you do if you’ve made an image of an entire disk? Many people will “carve out” the partition using dd with the skip and count options. You can save time and disk space by using the offset option with mount.
Using pretty much any partition manager (parted, fdisk, sfdisk, etc.), find out the byte boundaries of your desired partition. For example:
Using /mnt/external/vol2.work/vol2-1.big_image
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) unit
Unit? [compact]? B
(parted) print
Model: (file)
Disk /mnt/external/vol2.work/vol2-1.big_image: 40020664320B
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 32256B 32901119B 32868864B primary ext3 boot
2 32901120B 567544319B 534643200B primary linux-swap(v1)
3 567544320B 38461409279B 37893864960B primary linux-swap(v1)
4 38461409280B 40015987199B 1554577920B primary ntfs
Two swap partitions? That larger one might need some work, but the NTFS partition looks like it might be okay.
sudo mount -o ro,loop,offset=38461409280 -t auto vol2-1.big_image /mnt/test2
And it works! The (apparently quite old) NTFS filesystem is mounted.
$ ls /mnt/test2
arcldr.exe CONFIG.SYS NTDETECT.COM Program Files
arcsetup.exe Documents and Settings ntldr System Volume Information
AUTOEXEC.BAT IO.SYS pagefile.sys WINNT
boot.ini MSDOS.SYS Paragon HDM
Jesse Alter
Senior Lead Software Engineer
I am a senior lead software engineer and Linux system administrator, with a keen interest in both artificial intelligence and retrocomputing. When I’m not navigating the leading edge of technology, I meander along technology’s “trailing edge” accompanied by the computers I grew up with – the Commodore 64, Amiga 500, and Apple II among others.