Image Acquisition & Mount

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Acquisition

Always acquire read-only and hash while you copy. Keep the original device write-blocked and work only on verified copies.

DD

bash
# Generate a raw, bit-by-bit image (no on-the-fly hashing)
dd if=/dev/sdb of=disk.img bs=4M status=progress conv=noerror,sync
# Verify integrity afterwards
sha256sum disk.img > disk.img.sha256

dc3dd / dcfldd

dc3dd is the actively maintained fork of dcfldd (DoD Computer Forensics Lab dd).

bash
# Create an image and calculate multiple hashes at acquisition time
sudo dc3dd if=/dev/sdc of=/forensics/pc.img hash=sha256,sha1 hashlog=/forensics/pc.hashes log=/forensics/pc.log bs=1M

Guymager

Graphical, multithreaded imager that supports raw (dd), EWF (E01/EWFX) and AFF4 output with parallel verification. Available in most Linux repos (apt install guymager).

bash
# Start in GUI mode
sudo guymager
# Or acquire from CLI (since v0.9.5)
sudo guymager --simulate --input /dev/sdb --format EWF --hash sha256 --output /evidence/drive.e01

AFF4 (Advanced Forensics Format 4)

AFF4 is Google’s modern imaging format designed for very large evidence (sparse, resumable, cloud-native).

bash
# Acquire to AFF4 using the reference tool
pipx install aff4imager
sudo aff4imager acquire /dev/nvme0n1 /evidence/nvme.aff4 --hash sha256

# Velociraptor can also acquire AFF4 images remotely
velociraptor --config server.yaml frontend collect --artifact Windows.Disk.Acquire --args device="\\.\\PhysicalDrive0" format=AFF4

FTK Imager (Windows & Linux)

You can download FTK Imager and create raw, E01 or AFF4 images:

bash
ftkimager /dev/sdb evidence --e01 --case-number 1 --evidence-number 1 \
          --description 'Laptop seizure 2025-07-22' --examiner 'AnalystName' --compress 6

EWF tools (libewf)

bash
sudo ewfacquire /dev/sdb -u evidence -c 1 -d "Seizure 2025-07-22" -e 1 -X examiner --format encase6 --compression best

Imaging Cloud Disks

AWS – create a forensic snapshot without shutting down the instance:

bash
aws ec2 create-snapshot --volume-id vol-01234567 --description "IR-case-1234 web-server 2025-07-22"
# Copy the snapshot to S3 and download with aws cli / aws snowball

Azure – use az snapshot create and export to a SAS URL.

Mount

Choosing the right approach

  1. Mount the whole disk when you want the original partition table (MBR/GPT).
  2. Mount a single partition file when you only need one volume.
  3. Always mount read-only (-o ro,norecovery) and work on copies.

Raw images (dd, AFF4-extracted)

bash
# Identify partitions
fdisk -l disk.img

# Attach the image to a network block device (does not modify the file)
sudo modprobe nbd max_part=16
sudo qemu-nbd --connect=/dev/nbd0 --read-only disk.img

# Inspect partitions
lsblk /dev/nbd0 -o NAME,SIZE,TYPE,FSTYPE,LABEL,UUID

# Mount a partition (e.g. /dev/nbd0p2)
sudo mount -o ro,uid=$(id -u) /dev/nbd0p2 /mnt

Detach when finished:

bash
sudo umount /mnt && sudo qemu-nbd --disconnect /dev/nbd0

EWF (E01/EWFX)

bash
# 1. Mount the EWF container
mkdir /mnt/ewf
ewfmount evidence.E01 /mnt/ewf

# 2. Attach the exposed raw file via qemu-nbd (safer than loop)
sudo qemu-nbd --connect=/dev/nbd1 --read-only /mnt/ewf/ewf1

# 3. Mount the desired partition
sudo mount -o ro,norecovery /dev/nbd1p1 /mnt/evidence

Alternatively convert on the fly with xmount:

bash
xmount --in ewf evidence.E01 --out raw /tmp/raw_mount
mount -o ro /tmp/raw_mount/image.dd /mnt

LVM / BitLocker / VeraCrypt volumes

After attaching the block device (loop or nbd):

bash
# LVM
sudo vgchange -ay               # activate logical volumes
sudo lvscan | grep "/dev/nbd0"

# BitLocker (dislocker)
sudo dislocker -V /dev/nbd0p3 -u -- /mnt/bitlocker
sudo mount -o ro /mnt/bitlocker/dislocker-file /mnt/evidence

kpartx helpers

kpartx maps partitions from an image to /dev/mapper/ automatically:

bash
sudo kpartx -av disk.img  # creates /dev/mapper/loop0p1, loop0p2 …
mount -o ro /dev/mapper/loop0p2 /mnt

Common mount errors & fixes

ErrorTypical CauseFix
cannot mount /dev/loop0 read-onlyJournaled FS (ext4) not cleanly unmounteduse -o ro,norecovery
bad superblock …Wrong offset or damaged FScalculate offset (sector*size) or run fsck -n on a copy
mount: unknown filesystem type 'LVM2_member'LVM containeractivate volume group with vgchange -ay

Clean-up

Remember to umount and disconnect loop/nbd devices to avoid leaving dangling mappings that can corrupt further work:

bash
umount -Rl /mnt/evidence
kpartx -dv /dev/loop0  # or qemu-nbd --disconnect /dev/nbd0

References

  • AFF4 imaging tool announcement & specification: https://github.com/aff4/aff4
  • qemu-nbd manual page (mounting disk images safely): https://manpages.debian.org/qemu-system-common/qemu-nbd.1.en.html

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