Added a virtfs.sh tool to create file systems for the SD card.

tools/virtfs.sh~

-#!/usr/bin/env bash
-
-# Input params.
-root_dir_1=datafs
-root_dir_2=rootfs
-partition_file_1=datafs.ext4
-partition_file_2=rootfs.ext4
-partition_size_1_megs=500
-partition_size_2_megs=28000
-img_file=virtualfs-ext4.img
-block_size=512
-
-# Calculated params.
-mega="$(echo '2^20' | bc)"
-partition_size_1=$(($partition_size_1_megs * $mega))
-partition_size_2=$(($partition_size_2_megs * $mega))
-
-# Create a test directory to convert to ext2.
-mkdir -p "${root_dir_1}"
-echo content-1 > "${root_dir_1}/file-1"
-mkdir -p "${root_dir_2}"
-echo content-2 > "${root_dir_2}/file-2"
-
-# Create the 2 raw ext2 images.
-rm -f "${partition_file_1}"
-mke2fs \
-  -t ext4 \
-  -d "${root_dir_1}" \
-  -r 1 \
-  -N 0 \
-  -m 5 \
-  -L '' \
-  -O ^64bit \
-  "${partition_file_1}" \
-  "${partition_size_1_megs}M" \
-;
-rm -f "${partition_file_2}"
-mke2fs \
-  -t ext4 \
-  -d "${root_dir_2}" \
-  -r 1 \
-  -N 0 \
-  -m 5 \
-  -L '' \
-  -O ^64bit \
-  "${partition_file_2}" \
-  "${partition_size_2_megs}M" \
-;
-
-# Default offset according to
-part_table_offset=$((2**20))
-cur_offset=0
-bs=1024
-dd if=/dev/zero of="${img_file}" bs="${bs}" count=$(((${part_table_offset} + ${partition_size_1} + ${partition_size_2})/${bs})) skip="$((${cur_offset}/${bs}))"
-printf "
-type=83, size=$((${partition_size_1}/${block_size}))
-type=83, size=$((${partition_size_2}/${block_size}))
-" | sfdisk "${img_file}"
-cur_offset=$((${cur_offset} + ${part_table_offset}))
-# TODO: can we prevent this and use mke2fs directly on the image at an offset?
-# Tried -E offset= but could not get it to work.
-dd if="${partition_file_1}" of="${img_file}" bs="${bs}" seek="$((${cur_offset}/${bs}))"
-cur_offset=$((${cur_offset} + ${partition_size_1}))
-rm "${partition_file_1}"
-dd if="${partition_file_2}" of="${img_file}" bs="${bs}" seek="$((${cur_offset}/${bs}))"
-cur_offset=$((${cur_offset} + ${partition_size_2}))
-rm "${partition_file_2}"
-
-# Test the ext2 by mounting it with sudo.
-# sudo is only used for testing, the image is completely ready at this point.
-
-# losetup automation functions from:
-# https://stackoverflow.com/questions/1419489/how-to-mount-one-partition-from-an-image-file-that-contains-multiple-partitions/39675265#39675265
-loop-mount-partitions() (
-  set -e
-  img="$1"
-  dev="$(sudo losetup --show -f -P "$img")"
-  echo "${dev}" | sed -E 's/.*[^[:digit:]]([[:digit:]]+$)/\1/g'
-  for part in "${dev}p"*; do
-    if [ "${part}" = "${dev}p*" ]; then
-      # Single partition image.
-      part="${dev}"
-    fi
-    dst="/mnt/$(basename "${part}")"
-    echo "${dst}" 1>&2
-    sudo mkdir -p "${dst}"
-    sudo mount "${part}" "${dst}"
-  done
-)
-loop-unmount-partitions() (
-  set -e
-  for loop_id in "$@"; do
-    dev="/dev/loop${loop_id}"
-    for part in "${dev}p"*; do
-      if [ "${part}" = "${dev}p*" ]; then
-        part="${dev}"
-      fi
-      dst="/mnt/$(basename "${part}")"
-      sudo umount "${dst}"
-    done
-    sudo losetup -d "${dev}"
-  done
-)
-
-loop_id="$(loop-mount-partitions "${img_file}")"
-#sudo cmp /mnt/loop0p1/file-1 "${root_dir_1}/file-1"
-#sudo cmp /mnt/loop0p2/file-2 "${root_dir_2}/file-2"
-loop-unmount-partitions "${loop_id}"