114 lines
3.9 KiB
Bash
Executable File
114 lines
3.9 KiB
Bash
Executable File
#!/bin/sh
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# Copyright (C) 2023 Umorpha Systems
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# SPDX-License-Identifier: AGPL-3.0-or-later
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# This script is intended to work both in an initramfs and as a
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# developer-friendly tool on a real OS. Therefore, it has very few
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# dependencies and must be tolerant of different implementations:
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#
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# - sh (bash or busybox)
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# - getopt (busybox or util-linux)
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# - mkdir (busybox or coreutils)
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# - mount (util-linux)
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set -eu
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usage() {
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echo "Usage: $0 OPTIONS"
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echo "Mount devices using the Umorpha overlay-partition scheme."
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echo
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echo "OPTIONS:"
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echo " -h, --help Show this help text"
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echo " --root SPEC (required) The read-only root device ant its mount arguments"
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echo " --overlay SPEC (required) The writable overlay device ant its mount arguments"
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echo " --boot SPEC (optional) The device to mount at /boot"
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echo " --basedir DIR (required) Scratch directory to mount the root device and the overlay device"
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echo " --final-mountpoint DIR (optional) Where to mount the overlayfs (default: \${basedir}/mnt"
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echo
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echo "A SPEC is of the form"
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echo " DEVICE[:[FSTYPE][:OPTS]]"
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echo "If FSTYPE value isn't present, or is empty, then \`auto\` is used."
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}
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main() {
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mode=run
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if O=$(getopt -n "${0##*/}" -l help,root:,overlay:,boot:,basedir:,final-mountpoint: -o h -- "$@"); then
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eval "set -- $O"
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while true; do
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case "$1" in
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--help|-h) usage; exit 0;;
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--root) root_all=$2; shift 2;;
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--overlay) overlay_all=$2; shift 2;;
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--boot) boot_all=$2; shift 2;;
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--basedir) basedir=$2; shift 2;;
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--final-mountpoint) union_mnt=$2; shift 2;;
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--) shift; break;;
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esac
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done
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if [[ "$#" -gt 0 ]]; then
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echo >&2 "${0##*/}: unexpected positional arguments: $*"
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mode=error
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fi
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if [[ -z "${root_all:-}" ]]; then
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echo >&2 "${0##*/}: missing required --root flag"
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mode=error
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fi
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if [[ -z "${overlay_all:-}" ]]; then
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echo >&2 "${0##*/}: missing required --overlay flag"
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mode=error
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fi
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if [[ -z "${basedir:-}" ]]; then
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echo >&2 "${0##*/}: missing required --basedir flag"
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mode=error
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fi
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else
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mode=error
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fi
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if [[ $mode == error ]]; then
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echo "Try '${0##*/} --help' for more information."
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exit 2
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fi
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IFS=: read -r root_dev root_typ root_opt < <(echo "$root_all")
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root_mnt=$basedir/root
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IFS=: read -r overlay_dev overlay_typ overlay_opt < <(echo "$overlay_all")
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overlay_mnt=$basedir/overlay
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union_dev=umorpha-rootfs
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union_typ=overlay
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# BusyBox ash supports weird Bash-isms like "<(process
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# substitution)" and the special "[[" syntax, but supporting
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# "+=" to append to a variable is too much bloat!??
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union_opt=''
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union_opt="${union_opt:+${union_opt},}lowerdir=${root_mnt}"
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union_opt="${union_opt:+${union_opt},}upperdir=${overlay_mnt}/upperdir"
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union_opt="${union_opt:+${union_opt},}workdir=${overlay_mnt}/workdir"
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# > Offline changes to the lower tree are only allowed if the
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# > "metadata only copy up", "inode index", "xino" and
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# > "redirect_dir" features have not been used.
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#
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# -- https://www.kernel.org/doc/html/v6.6/filesystems/overlayfs.html#changes-to-underlying-filesystems
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union_opt="${union_opt:+${union_opt},}metacopy=off"
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union_opt="${union_opt:+${union_opt},}index=off"
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union_opt="${union_opt:+${union_opt},}xino=off"
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union_opt="${union_opt:+${union_opt},}redirect_dir=off"
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union_mnt=${union_mnt:-${basedir:-}/mnt}
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if [[ -n "${boot_all:-}" ]]; then
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IFS=: read -r boot_dev boot_typ boot_opt < <(echo "$boot_all")
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boot_mnt=$union_mnt/boot
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fi
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set -x
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mount --mkdir -t "${root_typ:-auto}" -o "$root_opt" "$root_dev" "$root_mnt"
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mount --mkdir -t "${overlay_typ:-auto}" -o "$overlay_opt" "$overlay_dev" "$overlay_mnt"
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mkdir -p -- "$overlay_mnt/upperdir" "$overlay_mnt/workdir"
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mount --mkdir -t "${union_typ:-auto}" -o "$union_opt" "$union_dev" "$union_mnt"
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if [[ -n "${boot_all:-}" ]]; then
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mount --mkdir -t "${boot_typ:-auto}" -o "$boot_opt" "$boot_dev" "$boot_mnt"
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fi
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}
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main "$@"
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