How to create a multi partition SD disk image without root privileges?

Question

Is it possible to create a complete SD image in linux without having root privileges (that is, no loopback mount)? I'm looking for a way to automate embedded system image creation. The image should include a specific partition structure and partitions formatted to FAT and ext2 populated with files from the build system. JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Minimal runnable sfdisk + mke2fs example without sudo In this example, we will create, without sudo or setsuid, an image file that contains two ext2 partitions, each populated with files from a host directory. We will then use sudo losetup just to mount the partitions to test that the Linux kernel can actually read them as explained at: How to mount one partition from an image file that contains multiple partitions on Linux? For more details, see: sfdisk: deals with the partition table: https://superuser.com/questions/332252/how-to-create-and-format-a-partition-using-a-bash-script/1132834#1132834 mke2fs: deals with EXT formatting of partitions: https://superuser.com/questions/605196/how-to-create-ext2-image-without-superuser-rights/1366762#1366762 The example: #!/usr/bin/env bash # Input params. root_dir_1=root1 root_dir_2=root2 partition_file_1=part1.ext2 partition_file_2=part2.ext2 partition_size_1_megs=32 partition_size_2_megs=32 img_file=img.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 \ -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 \ -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" Tested on Ubuntu 18.04. GitHub upstream.