I'm playing with VM's and would like to access a disk image file directly.  The VM is Windows 7.  The filesystem should be NTFS.

 

If I use Windows 10 file explorer and right click vdisk1.img and select "Mount" I receive the error message "The disc image file is corrupted."

 

If I try to mount from the unRAID console:

mount -r -t ntfs -o loop /mnt/disks/Windows/vdisk1.img /mnt/test

 

I get NTFS signature is missing.  Failed to mount '/dev/loop2': Invalid argument

 

What am I doing wrong?

The normal thing would be to go into the settings for the VM and assign the vdisk file as an additional drive.

Wouldn't I need to setup a 2nd VM using a different vdisk to do that?  I'd rather mount the vdisk.img if I can get the syntax correct.

Wouldn't I need to setup a 2nd VM using a different vdisk to do that?  I'd rather mount the vdisk.img if I can get the syntax correct.

you can have multiple vdisk files assigned to a VM (just like you can have multiple physical disks on a physical PC).  Trying to mount it the way you have been trying is not that easy as the mount process has to be one that understands the internal structure of the vdisk.

I understand multiple vdisks.  I guess what I am saying is this vdisk holds the OS.  In order to add it as an additional drive, I need to create another VM and use a different bootable vdisk, then add the secondary.

 

With VMware, I would do something like this to map the disk to Z:\ allowing me to directly read/write data:

vmware-mount /m:w z: "c:\vm\win7\win7.vmdk"

 

Obviously we're not dealing with VMware here, but I'm looking to achieve a similar solution.

 

Trying to mount it the way you have been trying is not that easy as the mount process has to be one that understands the internal structure of the vdisk.

 

How do I approach getting them to understand each other?

I figured it out.  I needed to specify the byte offset of where the partition begins.  For anyone who might have the same question in the future, here is what I did.

 

From the unRAID command console, display partition information of the vdisk:

fdisk -l /mnt/disks/Windows/vdisk1.img

 

I was after the values in red.  The output will looks something like this:

[pre]Disk vdisk1.img: 20 GiB, 21474836480 bytes, 41943040 sectors

Units: sectors of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disklabel type: dos

Disk identifier: 0xda00352d

 

Device      Boot  Start      End  Sectors  Size Id Type

vdisk1.img1 *      2048  206847  204800  100M  7 HPFS/NTFS/exFAT

vdisk1.img2      206848 41940991 41734144 19.9G  7 HPFS/NTFS/exFAT[/pre]

 

To find the offset in bytes, multiply the sector start value by the sector size to get the offset in bytes.  In this case, I wanted to mount vdisk1.img2. 

206848 * 512 = 105906176

 

Final command to mount the vdisk NTFS partition as read-only:

mount -r -t ntfs -o loop,offset=105906176 /mnt/disks/Windows/vdisk1.img /mnt/test

Automating mounting disk images would be a nice addition to a plugin like Unassigned Devices...

 

@dlandon

 

 

Edited February 1, 20206 yr by Dav3

On 2/1/2020 at 1:15 AM, Dav3 said:

Automating mounting disk images would be a nice addition to a plugin like Unassigned Devices...

 

@dlandon

 

 

+1 / bump 

Yes it would 😉
I am using:

expr [sector size value] \* [start sector value]

in Windows Terminal when ssh-ing into my Unraid server. 
I doubleclick on the values, richtclick to quickly copy and again rightclick to quickly paste on the cursor spot for quickly calculating and copying the result with all those quickclicks I just mentioned for the offset part of the ``mount`` command line. 
It's the quickest way I know. 
- and I sound like a duck right now 🤣
It would be nice to have a GUI to mount an img file and  select the disks in the vdisk img without doing the procedure above. 

 

Edited April 28, 20215 yr by Ymetro
forgot to mention Windows Terminal to SSH into Unraid server from my Windows 10 PC

I have taken a script from https://www.howtogeek.com/devops/how-to-mount-a-qemu-virtual-disk-image/ and modified it so it works with my disk image:

 

#!/bin/bash
# set -x # Set debug mode

image=/mnt/disks/WSC2LFGJ/Backups/Me/PC/Drives/c.img
mount=/mnt/disks/c
partition_offset=240123904

# Get partition information
echo "=== Partition Information ==="
fdisk -l "$image"

start=$(fdisk -l "$image" | grep '^/'"$image"'3' | awk '{print $2}') # Get NTFS partition start sector (partition 3)
echo "\nNTFS Partition Start Sector: $start"
sectors=$(fdisk -l "$image" | grep '^Units:' | awk '{print $5}' | cut -d',' -f1) # Show sector size
echo "Sector size: $sectors"
offset=$((start * sectors)) # Calculate offset
echo "Calculated offset: $offset"

mkdir $mount

# Try mounting with verbose output
# mount -v -r -o loop,offset=$offset "$image" $mount
mount -r -t ntfs -o loop,offset=$partition_offset "$image" $mount

 

Edited February 6, 20251 yr by Bluscream

Okay, with the help of cursor, ive modified this even further; find the scripts here:
https://github.com/Bluscream/Scripts/blob/7f71d301da15391585264c1ca6e7ed8ef7f82b79/unraid/config/plugins/user.scripts/scripts/image-disk/script
https://github.com/Bluscream/Scripts/blob/7f71d301da15391585264c1ca6e7ed8ef7f82b79/unraid/config/plugins/user.scripts/scripts/mount-image/script

https://github.com/Bluscream/Scripts/blob/7f71d301da15391585264c1ca6e7ed8ef7f82b79/unraid/config/plugins/user.scripts/scripts/mount-images/script

basically

#!/bin/bash

SCRIPT_PATH="/boot/config/plugins/user.scripts/scripts/mount-image/script"
if [[ ! -f "$SCRIPT_PATH" ]]; then
    echo "Error: Mount script not found at $SCRIPT_PATH"
    exit 1
fi
if [[ $EUID -ne 0 ]]; then
    echo "Error: This script must be run as root (use sudo)"
    exit 1
fi

mount_image() {
    echo "=== Mounting $1 ==="
    # bash "$SCRIPT_PATH" info --image "$1"
    bash "$SCRIPT_PATH" mount --image "$1" --partition "$2" --readonly &
    echo "   Background process started (PID: $!)"
    echo
}

bash "$SCRIPT_PATH" unmount
rm -rf /mnt/images/*/

# Mount specific partitions using their actual labels
mount_image "/mnt/user/backups/xxx/PC/Drives/xxx-pc.img" "Win 11 Pro"
mount_image "/mnt/user/backups/xxx/Laptop/drives/xxx-laptop.img" "Windows"
mount_image "/mnt/user/backups/xxx/Server/HomeAssistant/HASS_USB.img" "hassos-data"
# mount_image "/mnt/user/backups/xxx/Server/HomeAssistant/hass-sd_broken.img" "HomeAssistant SD"

echo "=== All mount operations started in background ==="
echo "Each mount process is waiting for Enter key to unmount"
echo "To unmount all disks at once, run: $SCRIPT_PATH unmount"
echo "To check mounted disks, run: $SCRIPT_PATH list"
echo
echo "Background processes:"
jobs

Edited July 29, 2025Jul 29 by Bluscream