When working with forensic disk images in an Ubuntu 14.04 x64 VM (VirtualBox on Windows 7 host), attempting to mount an XFS filesystem with:

mount -o ro,loop,offset=1048576 -t xfs /media/mountdevicesource/ewf1 /media/mountdest

Results in the frustrating error:

mount: cannot mount block device /dev/loop0 read-only

This issue typically stems from one of these technical factors:

• Incorrect offset calculation for the filesystem
• Missing XFS filesystem support in the kernel
• Permission issues with the loop device
• Corruption in the forensic image
• VirtualBox storage controller configuration

First, verify XFS support is installed:

sudo apt-get install xfsprogs
modprobe xfs

Try mounting with explicit loop device allocation:

sudo losetup -r -o 1048576 /dev/loop0 /media/mountdevicesource/ewf1
sudo mount -t xfs -o ro /dev/loop0 /media/mountdest

If the issue persists, verify the offset calculation using file:

file -s /dev/loop0

For EWF (EnCase) images specifically:

sudo ewfmount /media/mountdevicesource/ewf1 /mnt/ewf
sudo losetup -r -o 1048576 /dev/loop0 /mnt/ewf/ewf1
sudo mount -t xfs -o ro /dev/loop0 /media/mountdest

Ensure your VM storage controller is configured correctly:

VBoxManage storagectl "VM Name" --name "SATA Controller" --add sata --controller IntelAHCI --hostiocache on

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When attempting forensic analysis on disk images, the standard mount command structure is:

mount -o ro,loop,offset=1048576 -t xfs /path/to/image /mount/point

Key parameters worth examining:

• -o ro: Read-only mode (critical for forensic integrity)
• loop: Loop device mounting
• offset=1048576: 1MB offset (512-byte sectors × 2048)

The error typically manifests in three contexts:

# Scenario 1: Basic loop mounting
sudo mount -o ro,loop forensic.img /mnt/analysis
mount: cannot mount /dev/loop0 read-only

# Scenario 2: Offset mounting 
sudo mount -o ro,loop,offset=1048576 disk.raw /mnt/evidence
mount: cannot mount block device /dev/loop1 read-only

# Scenario 3: XFS-specific cases
sudo mount -o ro,loop,offset=2097152 -t xfs partition.img /mnt/xfs
mount: cannot mount /dev/loop2 read-only

Before attempting fixes, gather system information:

# Check loop module status
lsmod | grep loop

# Verify kernel support
cat /boot/config-$(uname -r) | grep -E "CONFIG_BLK_DEV_LOOP|CONFIG_XFS_FS"

# Examine current loop devices
losetup -l

These approaches have proven effective in production environments:

Method 1: Explicit loop device assignment

sudo losetup -r -o 1048576 /dev/loop0 /media/mountdevicesource/ewf1
sudo mount -t xfs -o ro /dev/loop0 /media/mountdest

Method 2: Alternative offset specification

sudo mount -o ro,loop,offset=$((512*2048)) -t xfs \
/media/mountdevicesource/ewf1 /media/mountdest

Method 3: Forensic toolkit approach

sudo ewfmount /media/mountdevicesource/ewf1 /mnt/ewf
sudo losetup -r -o 1048576 /dev/loop0 /mnt/ewf/ewf1
sudo mount -t xfs -o ro,norecovery /dev/loop0 /media/mountdest

For complex forensic scenarios, additional parameters may be necessary:

# Disable journal recovery for damaged XFS
sudo mount -t xfs -o ro,norecovery,noquota /dev/loop0 /mnt/forensic

# Combine with debug output
sudo mount -v -t xfs -o ro,loop,offset=1048576,noload \
/media/source/image.dd /mnt/target 2>&1 | tee mount.log

The VirtualBox environment introduces specific considerations:

• Enable nested virtualization if available
• Allocate sufficient base memory (≥4GB recommended)
• Verify shared folder permissions when mounting evidence
• Consider raw device mapping for better performance