Loop mounting a Raspberry Pi image file under Linux

Loop mounting allows you to mount an image file on a Linux host.

Install kpartx

sudo apt install kpartx

Create an image file from an SD card

sudo umount /dev/sdf1
sudo umount /dev/sdf2
sudo dd status=progress if=/dev/sdf of=2017-04-10-gateway-build.img

Helper scripts

In the tools directory you'll find a couple of helper scripts which automate the process of setting up the loop mounts and mounting/unmounting. mount-img.sh will create the loop mounts and mount the root partition. umount-img.sh undoes the work done by mount-img.sh.

Manual steps required for loop mounting

Create the loop mounts

sudo kpartx -v -a 2017-04-10-gateway-build.img

Mount the loop

/dev/mapper/loop0p1 will correspond to the boot partition, and /dev/mapper/loop0p2 will correspond to the root partition.

sudo mkdir -p rpi-root
sudo mount /dev/mapper/loop0p1 rpi-root

Unmount the loop when finished

sudo umount rpi-root

Remove the loop device

kpartx -v -d 2017-04-10-gateway-build.img