Circlean/shell_utils/basic_mount_image.sh

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#!/bin/bash
# Last update 16/05/2023 (dd/mm/yyyy)
# This script will mount a given image in loop mode.
# Make sure to change the path and offsets for the image you use. You can get
# the correct offsets using `file $PATH_TO_IMAGE` or fdisk.
# To make debugging easier
echo "KittenGroomer: in mount_image.sh" 1>&2
if [ "$(id -u)" != "0" ]; then
echo "This script must be run as root" 1>&2
exit 1
fi
set -e
#set -x
# Double check the path and offsets as noted above!
# Path to the image
IMAGE=''
# Start sector of boot (first) partition
BOOT_START=`sfdisk -J ${IMAGE} | grep -m 1 start | sed 's/"start":\|"\|,//g'`
# Amount of sectors of boot (first) partition
BOOT_SIZE=`sfdisk -J ${IMAGE} | grep -m 2 size | tail -n +2 | sed 's/"size":\|"\|,//g'`
# Start sector of root (second) partition
ROOT_START=`sfdisk -J ${IMAGE} | grep -m 2 start | tail -n +2 | sed 's/"start":\|"\|,//g'`
# Amount of sectors of root (second) partition
ROOT_SIZE=`sfdisk -J ${IMAGE} | grep -m 3 size | tail -n +3 | sed 's/"size":\|"\|,//g'`
# Locations you'd like the partitions mounted
BOOT_PATH='/mnt/rpi-boot'
ROOTFS_PATH='/mnt/rpi-root'
# Calculate offsets for each partition
offset_boot=$[BOOT_START * 512]
sizelimit_boot=$[BOOT_SIZE * 512]
offset_rootfs=$[ROOT_START * 512]
sizelimit_rootfs=$[ROOT_SIZE * 512]
# TODO: add logic for creating directories if they aren't already there
mkdir -p ${BOOT_PATH}
mkdir -p ${ROOTFS_PATH}
# Mount each partition in loop mode
mount -o loop,offset=${offset_boot},sizelimit=${sizelimit_boot} ${IMAGE} ${BOOT_PATH}
mount -o loop,offset=${offset_rootfs},sizelimit=${sizelimit_rootfs} ${IMAGE} ${ROOTFS_PATH}
echo "Image mounted" 1>&2