--- /dev/null
+#!/bin/bash
+
+# Buildroot wrapper to the collection of ext2/3/4 filesystem tools:
+# - genext2fs, to generate ext2 filesystem images
+# - tune2fs, to modify an ext2/3/4 filesystem (possibly in an image file)
+# - e2fsck, to check and fix an ext2/3/4 filesystem (possibly in an image file)
+
+set -e
+
+main() {
+ local OPT OPTARG
+ local nb_blocks nb_inodes nb_res_blocks root_dir image gen rev label uuid
+ local -a genext2fs_opts
+ local -a tune2fs_opts
+ local tune2fs_O_opts
+
+ # Default values
+ gen=2
+ rev=1
+
+ while getopts :hb:i:r:d:o:G:R:l:u: OPT; do
+ case "${OPT}" in
+ h) help; exit 0;;
+ b) nb_blocks=${OPTARG};;
+ i) nb_inodes=${OPTARG};;
+ r) nb_res_blocks=${OPTARG};;
+ d) root_dir="${OPTARG}";;
+ o) image="${OPTARG}";;
+ G) gen=${OPTARG};;
+ R) rev=${OPTARG};;
+ l) label="${OPTARG}";;
+ u) uuid="${OPTARG}";;
+ :) error "option '%s' expects a mandatory argument\n" "${OPTARG}";;
+ \?) error "unknown option '%s'\n" "${OPTARG}";;
+ esac
+ done
+
+ # Sanity checks
+ if [ -z "${root_dir}" ]; then
+ error "you must specify a root directory with '-d'\n"
+ fi
+ if [ -z "${image}" ]; then
+ error "you must specify an output image file with '-o'\n"
+ fi
+ case "${gen}:${rev}" in
+ 2:0|2:1|3:1|4:1)
+ ;;
+ 3:0|4:0)
+ error "revision 0 is invalid for ext3 and ext4\n"
+ ;;
+ *) error "unknown ext generation '%s' and/or revision '%s'\n" \
+ "${gen}" "${rev}"
+ ;;
+ esac
+
+ # calculate needed inodes
+ if [ -z "${nb_inodes}" ]; then
+ nb_inodes=$(find "${root_dir}" | wc -l)
+ nb_inodes=$((nb_inodes+400))
+ fi
+
+ # calculate needed blocks
+ if [ -z "${nb_blocks}" ]; then
+ # size ~= superblock, block+inode bitmaps, inodes (8 per block),
+ # blocks; we scale inodes / blocks with 10% to compensate for
+ # bitmaps size + slack
+ nb_blocks=$(du -s -k "${root_dir}" |sed -r -e 's/[[:space:]]+.*$//')
+ nb_blocks=$((500+(nb_blocks+nb_inodes/8)*11/10))
+ fi
+
+ # Upgrade to rev1 if needed
+ if [ ${rev} -ge 1 ]; then
+ tune2fs_O_opts+=",filetype"
+ fi
+
+ # Add a journal for ext3 and above
+ if [ ${gen} -ge 3 ]; then
+ tune2fs_opts+=( -j -J size=1 )
+ # we add 1300 blocks (a bit more than 1 MiB, assuming 1KiB blocks)
+ # for the journal
+ # Note: I came to 1300 blocks after trial-and-error checks. YMMV.
+ nb_blocks=$((nb_blocks+1300))
+ fi
+
+ # Add ext4 specific features
+ if [ ${gen} -ge 4 ]; then
+ tune2fs_O_opts+=",extents,uninit_bg,dir_index"
+ fi
+
+ # Add our -O options (there will be at most one leading comma, remove it)
+ if [ -n "${tune2fs_O_opts}" ]; then
+ tune2fs_opts+=( -O "${tune2fs_O_opts#,}" )
+ fi
+
+ # Add the label if specified
+ if [ -n "${label}" ]; then
+ tune2fs_opts+=( -L "${label}" )
+ fi
+
+ # Generate the filesystem
+ genext2fs_opts=( -b ${nb_blocks} -N ${nb_inodes} -d "${root_dir}" )
+ if [ -n "${nb_res_blocks}" ]; then
+ genext2fs_opts+=( -m ${nb_res_blocks} )
+ fi
+ genext2fs "${genext2fs_opts[@]}" "${image}"
+
+ # genext2fs does not generate a UUID, but fsck will whine if one
+ # is missing, so we need to add a UUID.
+ # Of course, this has to happen _before_ we run fsck.
+ # Also, some ext4 metadata are based on the UUID, so we must
+ # set it before we can convert the filesystem to ext4.
+ # If the user did not specify a UUID, we generate a random one.
+ # Although a random UUID may seem bad for reproducibility, there
+ # already are so many things that are not reproducible in a
+ # filesystem: file dates, file ordering, content of the files...
+ tune2fs -U "${uuid:-random}" "${image}"
+
+ # Upgrade the filesystem
+ if [ ${#tune2fs_opts[@]} -ne 0 ]; then
+ tune2fs "${tune2fs_opts[@]}" "${image}"
+ fi
+
+ # After changing filesystem options, running fsck is required
+ # (see: man tune2fs). Running e2fsck in other cases will ensure
+ # coherency of the filesystem, although it is not required.
+ # 'e2fsck -pDf' means:
+ # - automatically repair
+ # - optimise and check for duplicate entries
+ # - force checking
+ # Sending output to oblivion, as e2fsck can be *very* verbose,
+ # especially with filesystems generated by genext2fs.
+ # Exit codes 1 & 2 are OK, it means fs errors were successfully
+ # corrected, hence our little trick with $ret.
+ ret=0
+ e2fsck -pDf "${image}" >/dev/null || ret=$?
+ case ${ret} in
+ 0|1|2) ;;
+ *) errorN ${ret} "failed to run e2fsck on '%s' (ext%d)\n" \
+ "${image}" ${gen}
+ esac
+ printf "\n"
+ trace "e2fsck was successfully run on '%s' (ext%d)\n" "${image}" ${gen}
+ printf "\n"
+
+ # Remove count- and time-based checks, they are not welcome
+ # on embedded devices, where they can cause serious boot-time
+ # issues by tremendously slowing down the boot.
+ tune2fs -c 0 -i 0 "${image}"
+}
+
+help() {
+ cat <<_EOF_
+NAME
+ ${my_name} - Create an ext2/3/4 filesystem image
+
+SYNOPSIS
+ ${my_name} [OPTION]...
+
+DESCRIPTION
+ Create ext2/3/4 filesystem image from the content of a directory.
+
+ -b BLOCKS
+ Create a filesystem of BLOCKS 1024-byte blocs. The default is to
+ compute the required number of blocks.
+
+ -i INODES
+ Create a filesystem with INODES inodes. The default is to compute
+ the required number of inodes.
+
+ -r RES_BLOCKS
+ Create a filesystem with RES_BLOCKS reserved blocks. The default
+ is to reserve 0 block.
+
+ -d ROOT_DIR
+ Create a filesystem, using the content of ROOT_DIR as the content
+ of the root of the filesystem. Mandatory.
+
+ -o FILE
+ Create the filesystem in FILE. Madatory.
+
+ -G GEN -R REV
+ Create a filesystem of generation GEN (2, 3 or 4), and revision
+ REV (0 or 1). The default is to generate an ext2 revision 1
+ filesystem; revision 0 is invalid for ext3 and ext4.
+
+ -l LABEL
+ Create a filesystem with label LABEL. The default is to not set
+ a label.
+
+ -u UUID
+ Create filesystem with uuid UUID. The default is to set a random
+ UUID.
+
+ Exit status:
+ 0 if OK
+ !0 in case of error
+_EOF_
+}
+
+trace() { local msg="${1}"; shift; printf "%s: ${msg}" "${my_name}" "${@}"; }
+warn() { trace "${@}" >&2; }
+errorN() { local ret="${1}"; shift; warn "${@}"; exit ${ret}; }
+error() { errorN 1 "${@}"; }
+
+my_name="${0##*/}"
+main "$@"
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