overlayroot-sync

#!/bin/sh
#    Modified from overlayroot-chroot by Genki Yamauchi, 2022/09
#    			overlayroot-chroot - chroot wrapper script for overlayroot
#    			Copyright (C) 2012 Dustin Kirkland <kirkland@ubuntu.com>
#    			Authors: Dustin Kirkland <kirkland@ubuntu.com>

set -e
set -f # disable path expansion
REMOUNTS=""

error() {
	printf "ERROR: $@\n" 1>&2
}
fail() { [ $# -eq 0 ] || error "$@"; exit 1; }

info() {
	printf "INFO: $@\n" 1>&2
}


usage() {
	printf "Usage: ${0##*/} <file1_name> <file2_anme> ...\r\n" 1>&2
	printf "Both absolute path and relative path is ok for the file_name\r\n" 1>&2
}

if [ ! $# -gt 0 ]; then
		error "No argument for syncing"
    usage
		fail
fi

get_lowerdir() {
	local overlay=""
	overlay=$(awk \
		'$1 == "overlayroot" && $2 == "/" { print $0 }' /proc/mounts)
	if [ -n "${overlay}" ]; then
		lowerdir=${overlay##*lowerdir=}
		lowerdir=${lowerdir%%,*}
		if mountpoint "${lowerdir}" >/dev/null; then
			_RET="${lowerdir}"
		else
			fail "Unable to find the overlayroot lowerdir"
		fi
	else
		fail "Unable to find an overlayroot filesystem"
	fi
}

clean_exit() {
	local mounts="$1" rc=0 d="" lowerdir="" mp=""
	for d in ${mounts}; do
		if mountpoint ${d} >/dev/null; then
			umount ${d} || rc=1
		fi
	done
	for mp in $REMOUNTS; do
		mount -o remount,ro "${mp}" ||
			error "Note that [${mp}] is still mounted read/write"
	done
	[ "$2" = "return" ] && return ${rc} || exit ${rc}
}

# Try to find the overlayroot filesystem
get_lowerdir
lowerdir=${_RET}

recurse_mps=$(awk '$1 ~ /^\/dev\// && $2 ~ starts { print $2 }' \
	starts="^$lowerdir/" /proc/mounts)

mounts=
for d in proc run sys; do
	if ! mountpoint "${lowerdir}/${d}" >/dev/null; then
		mount -o bind "/${d}" "${lowerdir}/${d}" || fail "Unable to bind /${d}"
		mounts="$mounts $lowerdir/$d"
		trap "clean_exit \"${mounts}\" || true" EXIT HUP INT QUIT TERM
	fi
done

# Remount with read/write
for mp in "$lowerdir" $recurse_mps; do
	mount -o remount,rw "${mp}" &&
		REMOUNTS="$mp $REMOUNTS" ||
		fail "Unable to remount [$mp] writable"
done

# rsync 
for path in $@
do
	absolute_path=null
	case $path in
		/*) absolute_path=$path;;# $path is absolute
		*) absolute_path="${PWD}/${path}";;# $path is relative
	esac

	# If last charactor is "/", it is removed for rsync.
	case $path in
		*/) absolute_path=${absolute_path%?};;
	esac

	if [  -e $absolute_path ]; then # confirm path existance
		if [  -f $absolute_path ]; then
			# file copy

			rsync -av --mkpath --delete --exclude-from='/usr/local/share/overlayroot-sync/exclude_list' ${absolute_path} "${lowerdir}${absolute_path}"
		elif [  -d $absolute_path ]; then
			# directory copy
			rsync -av --mkpath --delete --exclude-from='/usr/local/share/overlayroot-sync/exclude_list' "${absolute_path}/" "${lowerdir}${absolute_path}"
		fi
	else
		error "${absolute_path} does not exist"
	fi
done

# Clean up mounts on exit
clean_exit "${mounts}" "return"
trap "" EXIT HUP INT QUIT TERM