Ejecutable mínimo sfdisk
+ mke2fs
ejemplo sinsudo
En este ejemplo, crearemos, sin sudo
o setsuid
, un archivo de imagen que contenga dos particiones ext2, cada una de ellas con archivos de un directorio de host.
Luego usaremos sudo losetup
solo para montar las particiones para probar que el kernel de Linux realmente puede leerlas como se explica en: /programming/1419489/how-to-mount-one-partition-from-an-image -archivo-que-contiene-particiones múltiples / 39675265 # 39675265
Para más detalles, ver:
El ejemplo:
#!/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:
# /programming/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"
Probado en Ubuntu 18.04. GitHub aguas arriba .