# ZFS boot stub for initramfs-tools.
#
# In the initramfs environment, the /init script sources this stub to
# override the default functions in the /scripts/local script.
#
# Enable this by passing boot=zfs on the kernel command line.
#
# $quiet, $root, $rpool, $bootfs come from the cmdline:
# shellcheck disable=SC2154

# Source the common functions
. /etc/zfs/zfs-functions

# Start interactive shell.
# Use debian's panic() if defined, because it allows to prevent shell access
# by setting panic in cmdline (e.g. panic=0 or panic=15).
# See "4.5 Disable root prompt on the initramfs" of Securing Debian Manual:
# https://www.debian.org/doc/manuals/securing-debian-howto/ch4.en.html
shell() {
	if command -v panic > /dev/null 2>&1
	then
		panic
	else
		/bin/sh
	fi
}

get_cmdline()
{
	_option="${1}"

	# shellcheck disable=SC2089
	grep -qiE "(^|[^\\](\\\\)* )(${_option})=(on|yes|1)( |$)" /proc/cmdline
}

# This runs any scripts that should run before we start importing
# pools and mounting any filesystems.
pre_mountroot()
{
	if command -v run_scripts > /dev/null 2>&1
	then
		if [ -f "/scripts/local-top" ] || [ -d "/scripts/local-top" ]
		then
			[ "${quiet}" != "y" ] && \
			    zfs_log_begin_msg "Running /scripts/local-top"
			run_scripts /scripts/local-top
			[ "${quiet}" != "y" ] && zfs_log_end_msg
		fi

	  if [ -f "/scripts/local-premount" ] || [ -d "/scripts/local-premount" ]
	  then
			[ "${quiet}" != "y" ] && \
			    zfs_log_begin_msg "Running /scripts/local-premount"
			run_scripts /scripts/local-premount
			[ "${quiet}" != "y" ] && zfs_log_end_msg
		fi
	fi
}

# If plymouth is available, hide the splash image.
disable_plymouth()
{
	if [ -x /bin/plymouth ] && /bin/plymouth --ping
	then
		/bin/plymouth hide-splash >/dev/null 2>&1
	fi
}

# Get a ZFS filesystem property value.
get_fs_value()
{
	_get_fs="${1}"
	_get_value="${2}"

	"${ZFS}" get -H -ovalue "${_get_value}" "${_get_fs}" 2> /dev/null
}

# Find the 'bootfs' property on pool $1.
# If the property does not contain '/', then ignore this
# pool by exporting it again.
find_rootfs()
{
	_find_rootfs_pool="${1}"

	# If 'POOL_IMPORTED' isn't set, no pool imported and therefore
	# we won't be able to find a root fs.
	[ -z "${POOL_IMPORTED}" ] && return 1

	# If it's already specified, just keep it mounted and exit
	# User (kernel command line) must be correct.
	if [ -n "${ZFS_BOOTFS}" ] && [ "${ZFS_BOOTFS}" != "zfs:AUTO" ]
	then
		return 0
	fi

	# Not set, try to find it in the 'bootfs' property of the pool.
	# NOTE: zpool does not support 'get -H -ovalue bootfs'...
	ZFS_BOOTFS=$("${ZPOOL}" list -H -obootfs "${_find_rootfs_pool}")

	# Make sure it's not '-' and that it starts with /.
	if [ "${ZFS_BOOTFS}" != "-" ] && \
		get_fs_value "${ZFS_BOOTFS}" mountpoint | grep -q '^/$'
	then
		# Keep it mounted
		POOL_IMPORTED=1
		return 0
	fi

	# Not boot fs here, export it and later try again..
	"${ZPOOL}" export "${_find_rootfs_pool}"
	POOL_IMPORTED=
	ZFS_BOOTFS=
	return 1
}

# Support function to get a list of all pools, separated with ';'
find_pools()
{
	_find_pools=$("${@}" 2> /dev/null | \
		sed -Ee '/ pool: | id: /!d' -e 's@.*: @@' | \
		tr '\n' ';')

	echo "${_find_pools%%;}" # Return without the last ';'.
}

# Get a list of all available pools
get_pools()
{
	if [ -n "${ZFS_POOL_IMPORT}" ]
	then
		echo "${ZFS_POOL_IMPORT}"
		return 0
	fi

	# Get the base list of available pools.
	_available_pools="$(find_pools "${ZPOOL}" import)"

	# Just in case - seen it happen (that a pool isn't visible/found
	# with a simple "zpool import" but only when using the "-d"
	# option or setting ZPOOL_IMPORT_PATH).
	if [ -d "/dev/disk/by-id" ]
	then
		_npools="$(find_pools "${ZPOOL}" import -d /dev/disk/by-id)"
		if [ -n "${_npools}" ]
		then
			# Because we have found extra pool(s) here, which wasn't
			# found 'normally', we need to force USE_DISK_BY_ID to
			# make sure we're able to actually import it/them later.
			USE_DISK_BY_ID='yes'

			if [ -n "${_available_pools}" ]
			then
				# Filter out duplicates (pools found with the simple
				# "zpool import" but which is also found with the
				# "zpool import -d ...").
				_npools="$(echo "${_npools}" | sed "s,${_available_pools},,")"

				# Add the list to the existing list of
				# available pools
				_available_pools="${_available_pools};${_npools}"
			else
				_available_pools="${_npools}"
			fi
		fi
	fi

	# Filter out any exceptions...
	if [ -n "${ZFS_POOL_EXCEPTIONS}" ]
	then
		_found=""
		_apools=""
		OLD_IFS="${IFS}" ; IFS=";"

		for pool in ${_available_pools}
		do
			for exception in ${ZFS_POOL_EXCEPTIONS}
			do
				[ "${pool}" = "${exception}" ] && continue 2
				_found="${pool}"
			done

			if [ -n "${_found}" ]
			then
				if [ -n "${_apools}" ]
				then
					_apools="${_apools};${pool}"
				else
					_apools="${pool}"
				fi
			fi
		done

		IFS="${OLD_IFS}"
		_available_pools="${_apools}"
	fi

	# Return list of available pools.
	echo "${_available_pools}"
}

# Import given pool $1
import_pool()
{
	_import_pool="${1}"

	# Verify that the pool isn't already imported
	# Make as sure as we can to not require '-f' to import.
	"${ZPOOL}" get -H -o value name,guid 2>/dev/null | \
		grep -Fxq "${_import_pool}" && return 0

	# For backwards compatibility, make sure that ZPOOL_IMPORT_PATH is set
	# to something we can use later with the real import(s). We want to
	# make sure we find all by* dirs, BUT by-vdev should be first (if it
	# exists).
	if [ -n "${USE_DISK_BY_ID}" ] && [ -z "${ZPOOL_IMPORT_PATH}" ]
	then
		dirs="$(for dir in /dev/disk/by-*
		do
			# Ignore by-vdev here - we want it first!
			echo "${dir}" | grep -q /by-vdev && continue
			[ ! -d "${dir}" ] && continue

			printf "%s" "${dir}:"
		done | sed 's,:$,,g')"

		if [ -d "/dev/disk/by-vdev" ]
		then
			# Add by-vdev at the beginning.
			ZPOOL_IMPORT_PATH="/dev/disk/by-vdev:"
		fi

		# ... and /dev at the very end, just for good measure.
		ZPOOL_IMPORT_PATH="${ZPOOL_IMPORT_PATH}${dirs}:/dev"
	fi

	# Needs to be exported for "zpool" to catch it.
	[ -n "${ZPOOL_IMPORT_PATH}" ] && export ZPOOL_IMPORT_PATH

	[ "${quiet}" != "y" ] && zfs_log_begin_msg \
		"Importing pool '${_import_pool}' using defaults"

	ZFS_CMD="${ZPOOL} import -N ${ZPOOL_FORCE} ${ZPOOL_IMPORT_OPTS}"
	ZFS_STDERR="$(${ZFS_CMD} "${_import_pool}" 2>&1)"
	ZFS_ERROR="${?}"
	if [ "${ZFS_ERROR}" != 0 ]
	then
		[ "${quiet}" != "y" ] && zfs_log_failure_msg "${ZFS_ERROR}"

		if [ -f "${ZPOOL_CACHE}" ]
		then
			[ "${quiet}" != "y" ] && zfs_log_begin_msg \
				"Importing pool '${_import_pool}' using cachefile."

			ZFS_CMD="${ZPOOL} import -c ${ZPOOL_CACHE} -N ${ZPOOL_FORCE}"
			ZFS_CMD="${ZFS_CMD} ${ZPOOL_IMPORT_OPTS}"
			ZFS_STDERR="$(${ZFS_CMD} "${_import_pool}" 2>&1)"
			ZFS_ERROR="${?}"
		fi

		if [ "${ZFS_ERROR}" != 0 ]
		then
			[ "${quiet}" != "y" ] && zfs_log_failure_msg "${ZFS_ERROR}"

			disable_plymouth
			echo ""
			echo "Command: ${ZFS_CMD} '${_import_pool}'"
			echo "Message: ${ZFS_STDERR}"
			echo "Error: ${ZFS_ERROR}"
			echo ""
			echo "Failed to import pool '${_import_pool}'."
			echo "Manually import the pool and exit."
			shell
		fi
	fi

	[ "${quiet}" != "y" ] && zfs_log_end_msg

	POOL_IMPORTED=1
	return 0
}

# Load ZFS modules
# Loading a module in a initrd require a slightly different approach,
# with more logging etc.
load_module_initrd()
{
	_retval=0

	ZFS_INITRD_PRE_MOUNTROOT_SLEEP=${ROOTDELAY:-0}

	if [ "${ZFS_INITRD_PRE_MOUNTROOT_SLEEP}" -gt 0 ]
	then
		[ "${quiet}" != "y" ] && \
			zfs_log_begin_msg "Delaying for up to '${ZFS_INITRD_PRE_MOUNTROOT_SLEEP}' seconds."
	fi

	START="$(/bin/date -u +%s)"
	END="$((START+ZFS_INITRD_PRE_MOUNTROOT_SLEEP))"
	while true
	do
		# Wait for all of the /dev/{hd,sd}[a-z] device nodes to appear.
		if command -v wait_for_udev > /dev/null 2>&1
		then
			wait_for_udev 10
		elif command -v wait_for_dev > /dev/null 2>&1
		then
			wait_for_dev
		fi

		# zpool import refuse to import without a valid /proc/self/mounts
		[ ! -f /proc/self/mounts ] && mount proc /proc

		# Load the module
		if load_module "zfs"
		then
			_retval=0
			break
		else
			_retval=1
		fi

		[ "$(/bin/date -u +%s)" -gt "${END}" ] && break
		sleep 1
	done

	if [ "${ZFS_INITRD_PRE_MOUNTROOT_SLEEP}" -gt 0 ]
	then
		[ "${quiet}" != "y" ] && zfs_log_end_msg
	fi

	[ "${_retval}" -ne 0 ] && return "${_retval}"

	if [ "${ZFS_INITRD_POST_MODPROBE_SLEEP}" -gt 0 ] 2>/dev/null
	then
		if [ "${quiet}" != "y" ]
		then
			zfs_log_begin_msg "Sleeping for" \
				"${ZFS_INITRD_POST_MODPROBE_SLEEP} seconds..."
		fi
		sleep "${ZFS_INITRD_POST_MODPROBE_SLEEP}"
		[ "${quiet}" != "y" ] && zfs_log_end_msg
	fi

	return "${_retval}"
}

# Mount a given filesystem
# Note: Filesystem must have either `canmount=on` or `canmount=noauto`.
#       This script only deals with "important" file system, such as those
#       that are relevant to the operation of the operating system.
#       Therefor we need to mount even those that have `canmount=noauto`.
#       However, if user have specifically specified `canmount=off`, then
#       we will assume that user knows what they're doing and ignore it.
mount_fs()
{
	_mount_fs="${1}"

	# Check that the filesystem exists
	"${ZFS}" list -oname -tfilesystem -H "${_mount_fs}" \
			 > /dev/null 2>&1 ||  return 1

	# Skip filesystems with canmount=off.  The root fs should not have
	# canmount=off, but ignore it for backwards compatibility just in case.
	if [ "${_mount_fs}" != "${ZFS_BOOTFS}" ]
	then
		_canmount="$(get_fs_value "${_mount_fs}" canmount)"
		[ "${_canmount}" = "off" ] && return 0
	fi

	# Need the _original_ datasets mountpoint!
	_mountpoint="$(get_fs_value "${_mount_fs}" mountpoint)"
	ZFS_CMD="mount.zfs -o zfsutil"
	if [ "${_mountpoint}" = "legacy" ] || [ "${_mountpoint}" = "none" ]
	then
		# Can't use the mountpoint property. Might be one of our
		# clones. Check the 'org.zol:mountpoint' property set in
		# clone_snap() if that's usable.
		_mountpoint1="$(get_fs_value "${_mount_fs}" org.zol:mountpoint)"
		if [ "${_mountpoint1}" = "legacy" ] ||
		   [ "${_mountpoint1}" = "none" ] ||
		   [ "${_mountpoint1}" = "-" ]
		then
			if [ "${_mount_fs}" != "${ZFS_BOOTFS}" ]
			then
				# We don't have a proper mountpoint and this
				# isn't the root fs.
				return 0
			fi
			if [ "${_mountpoint}" = "legacy" ]
			then
				ZFS_CMD="mount.zfs"
			fi
			# Last hail-mary: Hope 'rootmnt' is set!
			_mountpoint=""
		else
			_mountpoint="${_mountpoint1}"
		fi
	fi

	# Possibly decrypt a filesystem using native encryption.
	decrypt_fs "${_mount_fs}"

	[ "${quiet}" != "y" ] && \
	    zfs_log_begin_msg \
			"Mounting '${_mount_fs}' on '${rootmnt}/${_mountpoint}'"
	[ -n "${ZFS_DEBUG}" ] && \
	    zfs_log_begin_msg \
			"CMD: '${ZFS_CMD} ${_mount_fs} ${rootmnt}/${_mountpoint}'"

	ZFS_STDERR="$(${ZFS_CMD} "${_mount_fs}" "${rootmnt}/${_mountpoint}" 2>&1)"
	ZFS_ERROR="${?}"
	if [ "${ZFS_ERROR}" != 0 ]
	then
		[ "${quiet}" != "y" ] && zfs_log_failure_msg "${ZFS_ERROR}"

		disable_plymouth
		echo ""
		echo "Command: ${ZFS_CMD} ${_mount_fs} ${rootmnt}/${_mountpoint}"
		echo "Message: ${ZFS_STDERR}"
		echo "Error: ${ZFS_ERROR}"
		echo ""
		echo "Failed to mount ${_mount_fs} on ${rootmnt}/${_mountpoint}."
		echo "Manually mount the filesystem and exit."
		shell
	else
		[ "${quiet}" != "y" ] && zfs_log_end_msg
	fi

	return 0
}

# Unlock a ZFS native encrypted filesystem.
decrypt_fs()
{
	_decrypt_fs="${1}"

	# If pool encryption is active and the zfs command understands
	# '-o encryption'.
	_enc="$("${ZPOOL}" list -H -o feature@encryption "${_decrypt_fs%%/*}")"
	if [ "${_enc}" = 'active' ]
	then
		# Determine dataset that holds key for root dataset
		ENCRYPTIONROOT="$(get_fs_value "${_decrypt_fs}" encryptionroot)"
		KEYLOCATION="$(get_fs_value "${ENCRYPTIONROOT}" keylocation)"

		echo "${ENCRYPTIONROOT}" > /run/zfs_fs_name

		# If root dataset is encrypted...
		if [ "${ENCRYPTIONROOT}" != "-" ]
		then
			KEYSTATUS="$(get_fs_value "${ENCRYPTIONROOT}" keystatus)"
			# Continue only if the key needs to be loaded
			[ "${KEYSTATUS}" = "unavailable" ] || return 0

			# Try extensions first
			for key in "/etc/zfs/initramfs-tools-load-key" \
						   "/etc/zfs/initramfs-tools-load-key.d/"*
			do
				[ -r "${key}" ] || continue
				(. "${key}") && {
					# Successful return and actually-loaded key: we're done
					KEYSTATUS="$(get_fs_value "${ENCRYPTIONROOT}" keystatus)"
					[ "${KEYSTATUS}" = "unavailable" ] || return 0
				}
			done

			# Do not prompt if key is stored noninteractively,
			if [ "${KEYLOCATION}" != "prompt" ]
			then
				"${ZFS}" load-key "${ENCRYPTIONROOT}"

			# Prompt with plymouth, if active
			elif /bin/plymouth --ping 2>/dev/null
			then
				echo "plymouth" > /run/zfs_console_askpwd_cmd
				for _ in 1 2 3
				do
					plymouth ask-for-password --prompt \
							 "Encrypted ZFS password for ${ENCRYPTIONROOT}" | \
						"${ZFS}" load-key "${ENCRYPTIONROOT}" && break
				done

			# Prompt with systemd, if active
			elif [ -e /run/systemd/system ]
			then
				echo "systemd-ask-password" > /run/zfs_console_askpwd_cmd
				for _ in 1 2 3
				do
					systemd-ask-password \
						--no-tty \
						"Encrypted ZFS password for ${ENCRYPTIONROOT}" | \
						"${ZFS}" load-key "${ENCRYPTIONROOT}" && break
				done

			# Prompt with ZFS tty, otherwise
			else
				# Temporarily setting "printk" to "7" allows the prompt to
				# appear even when the "quiet" kernel option has been used.
				echo "load-key" > /run/zfs_console_askpwd_cmd
				read -r storeprintk _ < /proc/sys/kernel/printk
				echo 7 > /proc/sys/kernel/printk
				"${ZFS}" load-key "${ENCRYPTIONROOT}"
				echo "${storeprintk}" > /proc/sys/kernel/printk
			fi
		fi
	fi

	return 0
}

# Destroy a given filesystem.
destroy_fs()
{
	_destroy_fs="${1}"

	[ "${quiet}" != "y" ] && \
	    zfs_log_begin_msg "Destroying '${destroy_fs}'"

	ZFS_CMD="${ZFS} destroy ${destroy_fs}"
	ZFS_STDERR="$(${ZFS_CMD} 2>&1)"
	ZFS_ERROR="${?}"
	if [ "${ZFS_ERROR}" != 0 ]
	then
		[ "${quiet}" != "y" ] && zfs_log_failure_msg "${ZFS_ERROR}"

		disable_plymouth
		echo ""
		echo "Command: ${ZFS_CMD}"
		echo "Message: ${ZFS_STDERR}"
		echo "Error: ${ZFS_ERROR}"
		echo ""
		echo "Failed to destroy '${_destroy_fs}'."
		echo "Please make sure that it is not available."
		echo "Hint: Try:  zfs destroy -Rfn ${_destroy_fs}"
		echo "If this dryrun looks good, then remove the 'n' from '-Rfn'" \
			 "and try again."
		shell
	else
		[ "${quiet}" != "y" ] && zfs_log_end_msg
	fi

	return 0
}

# Clone snapshot $1 to destination filesystem $2
# Set 'canmount=noauto' and 'mountpoint=none' so that we get to keep
# manual control over it's mounting (i.e., make sure it's not automatically
# mounted with a 'zfs mount -a' in the init/systemd scripts).
clone_snap()
{
	_clone_snap="${1}"
	_clone_destfs="${2}"
	_clone_mountpoint="${3}"

	[ "${quiet}" != "y" ] && \
		zfs_log_begin_msg "Cloning '${_clone_snap}' to '${_clone_destfs}'"

	# Clone the snapshot into a dataset we can boot from
	# + We don't want this filesystem to be automatically mounted, we
	#   want control over this here and nowhere else.
	# + We don't need any mountpoint set for the same reason.
	# We use the 'org.zol:mountpoint' property to remember the mountpoint.
	ZFS_CMD="${ZFS} clone -o canmount=noauto -o mountpoint=none"
	ZFS_CMD="${ZFS_CMD} -o org.zol:mountpoint=${_clone_mountpoint}"
	ZFS_CMD="${ZFS_CMD} ${_clone_snap} ${_clone_destfs}"
	ZFS_STDERR="$(${ZFS_CMD} 2>&1)"
	ZFS_ERROR="${?}"
	if [ "${ZFS_ERROR}" != 0 ]
	then
		[ "${quiet}" != "y" ] && zfs_log_failure_msg "${ZFS_ERROR}"

		disable_plymouth
		echo ""
		echo "Command: ${ZFS_CMD}"
		echo "Message: ${ZFS_STDERR}"
		echo "Error: ${ZFS_ERROR}"
		echo ""
		echo "Failed to clone snapshot."
		echo "Make sure that any problems are corrected and then make sure"
		echo "that the dataset '${_clone_destfs}' exists and is bootable."
		shell
	else
		[ "${quiet}" != "y" ] && zfs_log_end_msg
	fi

	return 0
}

# Rollback a given snapshot.
rollback_snap()
{
	_rollback_snap="${1}"

	[ "${quiet}" != "y" ] && zfs_log_begin_msg "Rollback ${_rollback_snap}"

	ZFS_CMD="${ZFS} rollback -Rf ${_rollback_snap}"
	ZFS_STDERR="$(${ZFS_CMD} 2>&1)"
	ZFS_ERROR="${?}"
	if [ "${ZFS_ERROR}" != 0 ]
	then
		[ "${quiet}" != "y" ] && zfs_log_failure_msg "${ZFS_ERROR}"

		disable_plymouth
		echo ""
		echo "Command: ${ZFS_CMD}"
		echo "Message: ${ZFS_STDERR}"
		echo "Error: ${ZFS_ERROR}"
		echo ""
		echo "Failed to rollback snapshot."
		shell
	else
		[ "${quiet}" != "y" ] && zfs_log_end_msg
	fi

	return 0
}

# Get a list of snapshots, give them as a numbered list
# to the user to choose from.
ask_user_snap()
{
	_ask_snap="${1}"

	# We need to temporarily disable debugging. Set 'debug' so we
	# remember to enabled it again.
	if [ -n "${ZFS_DEBUG}" ]
	then
		unset ZFS_DEBUG
		set +x
		_debug=1
	fi

	# Because we need the resulting snapshot, which is sent on
	# stdout to the caller, we use stderr for our questions.
	echo "What snapshot do you want to boot from?" > /dev/stderr
	# shellcheck disable=SC2046
	IFS="
" set -- $("${ZFS}" list -H -oname -tsnapshot -r "${_ask_snap}")

	i=1
	for snap in "${@}"
	do
		echo "  ${i}: ${snap}"
		i="$((i + 1))"
	done > /dev/stderr

	# expr instead of test here because [ a -lt 0 ] errors out,
	# but expr falls back to lexicographical, which works out right
	_snapnr=0
	while expr "${_snapnr}" "<" 1 > /dev/null ||
	    expr "${_snapnr}" ">" "${#}" > /dev/null
	do
		printf "%s" "Snap nr [1-${#}]? " > /dev/stderr
		read -r _snapnr
	done

	# Re-enable debugging.
	if [ -n "${_debug}" ]
	then
		ZFS_DEBUG=1
		set -x
	fi

	eval echo '$'"${_snapnr}"
}

setup_snapshot_booting()
{
	_boot_snap="${1}"
	_retval=0

	# Make sure that the snapshot specified actually exists.
	if [ -z "$(get_fs_value "${_boot_snap}" type)" ]
	then
		# Snapshot does not exist (...@<null> ?)
		# ask the user for a snapshot to use.
		snap="$(ask_user_snap "${_boot_snap%%@*}")"
	fi

	# Separate the full snapshot ('${snap}') into it's filesystem and
	# snapshot names. Would have been nice with a split() function..
	_rootfs="${_boot_snap%%@*}"
	_snapname="${_boot_snap##*@}"
	ZFS_BOOTFS="${_rootfs}_${_snapname}"

	if ! get_cmdline 'rollback'
	then
		# If the destination dataset for the clone
		# already exists, destroy it. Recursively
		if [ -n "$(get_fs_value "${_rootfs}_${_snapname}" type)" ]
		then
			_filesystems="$("${ZFS}" list -oname -tfilesystem -H \
			    -r -Sname "${ZFS_BOOTFS}")"
			for fs in ${_filesystems}
			do
				destroy_fs "${_boot_snap}"
			done
		fi
	fi

	# Get all snapshots, recursively (might need to clone /usr, /var etc
	# as well).
	for s in $("${ZFS}" list -H -oname -tsnapshot -r "${_rootfs}" | \
	    grep "${_snapname}")
	do
		if get_cmdline 'rollback'
		then
			# Rollback snapshot
			rollback_snap "${s}" || _retval="$((_retval + 1))"
			ZFS_BOOTFS="${_rootfs}"
		else
			# Setup a destination filesystem name.
			# Ex: Called with 'rpool/ROOT/debian@snap2'
			#       rpool/ROOT/debian@snap2      => rpool/ROOT/debian_snap2
			#       rpool/ROOT/debian/boot@snap2 => rpool/ROOT/debian_snap2/boot
			#       rpool/ROOT/debian/usr@snap2  => rpool/ROOT/debian_snap2/usr
			#       rpool/ROOT/debian/var@snap2  => rpool/ROOT/debian_snap2/var
			_subfs="${s##"${_rootfs}"}"
			_subfs="${_subfs%%@"${_snapname}"}"

			_destfs="${_rootfs}_${_snapname}" # base fs.
			[ -n "${_subfs}" ] && _destfs="${_destfs}${_subfs}" # + sub fs.

			# Get the mountpoint of the filesystem, to be used
			# with clone_snap(). If legacy or none, then use
			# the sub fs value.
			_mountpoint="$(get_fs_value "${s%%@*}" mountpoint)"
			if [ "${_mountpoint}" = "legacy" ] || \
			   [ "${_mountpoint}" = "none" ]
			then
				if [ -n "${_subfs}" ]
				then
					_mountpoint="${_subfs}"
				else
					_mountpoint="/"
				fi
			fi

			# Clone the snapshot into its own
			# filesystem
			clone_snap "${s}" "${_destfs}" "${_mountpoint}" || \
			    _retval="$((_retval + 1))"
		fi
	done

	# If we haven't return yet, we have a problem...
	return "${_retval}"
}

# ================================================================

# This is the main function.
mountroot()
{
	# ----------------------------------------------------------------
	# I N I T I A L   S E T U P

	# ------------
	# Run the pre-mount scripts from /scripts/local-top.
	pre_mountroot

	# ------------
	# Support debug option
	if get_cmdline 'zfs_debug|zfs\.debug|zfsdebug'
	then
		ZFS_DEBUG=1
		mkdir /var/log
		#exec 2> /var/log/boot.debug
		set -x
	fi

	# ------------
	# Load ZFS module etc.
	if ! load_module_initrd
	then
		disable_plymouth
		echo ""
		echo "Failed to load ZFS modules."
		echo "Manually load the modules and exit."
		shell
	fi

	# ------------
	# Look for the cache file (if any).
	[ -f "${ZPOOL_CACHE}" ] || unset ZPOOL_CACHE
	[ -s "${ZPOOL_CACHE}" ] || unset ZPOOL_CACHE

	# ------------
	# Compatibility: 'ROOT' is for Debian GNU/Linux (etc),
	#		 'root' is for Redhat/Fedora (etc),
	#		 'REAL_ROOT' is for Gentoo
	if [ -z "${ROOT}" ]
	then
		[ -n "${root}" ] && ROOT="${root}"

		[ -n "${REAL_ROOT}" ] && ROOT="${REAL_ROOT}"
	fi

	# ------------
	# Where to mount the root fs in the initrd - set outside this script
	# Compatibility: 'rootmnt' is for Debian GNU/Linux (etc),
	#		 'NEWROOT' is for RedHat/Fedora (etc),
	#		 'NEW_ROOT' is for Gentoo
	if [ -z "${rootmnt}" ]
	then
		[ -n "${NEWROOT}" ] && rootmnt="${NEWROOT}"

		[ -n "${NEW_ROOT}" ] && rootmnt="${NEW_ROOT}"
	fi

	# ------------
	# No longer set in the defaults file, but it could have been set in
	# get_pools() in some circumstances. If it's something, but not 'yes',
	# it's no good to us.
	[ -n "${USE_DISK_BY_ID}" ] && [ "${USE_DISK_BY_ID}" != 'yes' ] && \
	    unset USE_DISK_BY_ID

	# ----------------------------------------------------------------
	# P A R S E   C O M M A N D   L I N E   O P T I O N S

	# This part is the really ugly part - there's so many options and
	# permutations 'out there', and if we should make this the 'primary'
	# source for ZFS initrd scripting, we need/should support them all.
	#
	# Supports the following kernel command line argument combinations
	# (in this order - first match win):
	#
	#   rpool=<pool>                (tries to finds bootfs automatically)
	#   bootfs=<pool>/<dataset>		(uses this for rpool - first part)
	#   rpool=<pool> bootfs=<pool>/<dataset>
	#   -B zfs-bootfs=<pool>/<fs>   (uses this for rpool - first part)
	#   rpool=rpool                 (default if none of the above is used)
	#   root=<pool>/<dataset>       (uses this for rpool - first part)
	#   root=ZFS=<pool>/<dataset>   (uses this for rpool - first part, without 'ZFS=')
	#   root=zfs:AUTO               (tries to detect both pool and rootfs)
	#   root=zfs:<pool>/<dataset>   (uses this for rpool - first part, without 'zfs:')
	#
	# Option <dataset> could also be <snapshot>
	# Option <pool> could also be <guid>

	# ------------
	# Support force option
	# In addition, setting one of zfs_force, zfs.force or zfsforce to
	# 'yes', 'on' or '1' will make sure we force import the pool.
	# This should (almost) never be needed, but it's here for
	# completeness.
	ZPOOL_FORCE=""
	if get_cmdline 'zfs_force|zfs\.force|zfsforce'
	then
		ZPOOL_FORCE="-f"
	fi

	# ------------
	# Look for 'rpool' and 'bootfs' parameter
	[ -n "${rpool}" ] && ZFS_RPOOL="${rpool#rpool=}"
	[ -n "${bootfs}" ] && ZFS_BOOTFS="${bootfs#bootfs=}"

	# ------------
	# If we have 'ROOT' (see above), but not 'ZFS_BOOTFS', then use
	# 'ROOT'
	[ -n "${ROOT}" ] && [ -z "${ZFS_BOOTFS}" ] && ZFS_BOOTFS="${ROOT}"

	# ------------
	# Check for the `-B zfs-bootfs=%s/%u,...` kind of parameter.
	# NOTE: Only use the pool name and dataset. The rest is not
	#       supported by OpenZFS (whatever it's for).
	if [ -z "${ZFS_RPOOL}" ]
	then
		# The ${zfs-bootfs} variable is set at the kernel command
		# line, usually by GRUB, but it cannot be referenced here
		# directly because bourne variable names cannot contain a
		# hyphen.
		#
		# Reassign the variable by dumping the environment and
		# stripping the zfs-bootfs= prefix.  Let the shell handle
		# quoting through the eval command:
		# shellcheck disable=SC2046
		eval ZFS_RPOOL="$(set | sed -n -e 's,^zfs-bootfs=,,p')"
	fi

	# ------------
	# No root fs or pool specified - do auto detect.
	if [ -z "${ZFS_RPOOL}" ] && [ -z "${ZFS_BOOTFS}" ]
	then
		# Do auto detect. Do this by 'cheating' - set 'root=zfs:AUTO'
		# which will be caught later
		ROOT='zfs:AUTO'
	fi

	# ----------------------------------------------------------------
	# F I N D   A N D   I M P O R T   C O R R E C T   P O O L

	# ------------
	if [ "${ROOT}" = "zfs:AUTO" ]
	then
		# Try to detect both pool and root fs.

		# If we got here, that means we don't have a hint so as to
		# the root dataset, but with root=zfs:AUTO on cmdline,
		# this says "zfs:AUTO" here and interferes with checks later
		ZFS_BOOTFS=

		[ "${quiet}" != "y" ] && \
		    zfs_log_begin_msg "Attempting to import additional pools."

		# Get a list of pools available for import
		if [ -n "${ZFS_RPOOL}" ]
		then
			# We've specified a pool - check only that
			POOLS="${ZFS_RPOOL}"
		else
			POOLS="$(get_pools)"
		fi

		OLD_IFS="${IFS}" ; IFS=";"
		for pool in ${POOLS}
		do
			[ -z "${pool}" ] && continue

			IFS="${OLD_IFS}" import_pool "${pool}"
			IFS="${OLD_IFS}" find_rootfs "${pool}" && break
		done
		IFS="${OLD_IFS}"

		[ "${quiet}" != "y" ] && zfs_log_end_msg "${ZFS_ERROR}"
	else
		# No auto - use value from the command line option.

		# Strip 'zfs:' and 'ZFS='.
		ZFS_BOOTFS="${ROOT#*[:=]}"

		# Strip everything after the first slash.
		ZFS_RPOOL="${ZFS_BOOTFS%%/*}"
	fi

	# Import the pool (if not already done so in the AUTO check above).
	if [ -n "${ZFS_RPOOL}" ] && [ -z "${POOL_IMPORTED}" ]
	then
		[ "${quiet}" != "y" ] && \
		    zfs_log_begin_msg "Importing ZFS root pool '${ZFS_RPOOL}'"

		import_pool "${ZFS_RPOOL}"
		find_rootfs "${ZFS_RPOOL}"

		[ "${quiet}" != "y" ] && zfs_log_end_msg
	fi

	if [ -z "${POOL_IMPORTED}" ]
	then
		# No pool imported, this is serious!
		disable_plymouth
		echo ""
		echo "Command: ${ZFS_CMD}"
		echo "Message: ${ZFS_STDERR}"
		echo "Error: ${ZFS_ERROR}"
		echo ""
		echo "No pool imported. Manually import the root pool"
		echo "at the command prompt and then exit."
		echo "Hint: Try:  zpool import -N ${ZFS_RPOOL}"
		shell
	fi

	# In case the pool was specified as guid, resolve guid to name
	pool="$("${ZPOOL}" get -H -o name,value name,guid | \
	    awk -v pool="${ZFS_RPOOL}" '$2 == pool { print $1 }')"
	if [ -n "${pool}" ]
	then
		# If ${ZFS_BOOTFS} contains guid, replace the guid portion with ${pool}.
		ZFS_BOOTFS="$(echo "${ZFS_BOOTFS}" | \
			sed -e "s/$("${ZPOOL}" get -H -o value guid "${pool}")/${pool}/g")"
		ZFS_RPOOL="${pool}"
	fi


	# ----------------------------------------------------------------
	# P R E P A R E   R O O T   F I L E S Y S T E M

	if [ -n "${ZFS_BOOTFS}" ]
	then
		# Booting from a snapshot?
		# Will overwrite the ZFS_BOOTFS variable like so:
		#   rpool/ROOT/debian@snap2 => rpool/ROOT/debian_snap2
		echo "${ZFS_BOOTFS}" | grep -q '@' && \
		    setup_snapshot_booting "${ZFS_BOOTFS}"
	fi

	if [ -z "${ZFS_BOOTFS}" ]
	then
		# Still nothing! Let the user sort this out.
		disable_plymouth
		echo ""
		echo "Error: Unknown root filesystem - no 'bootfs' pool property and"
		echo "       not specified on the kernel command line."
		echo ""
		echo "Manually mount the root filesystem on ${rootmnt} and then exit."
		echo "Hint: Try:  mount -o zfsutil -t zfs " \
			 "${ZFS_RPOOL:-rpool}/ROOT/system ${rootmnt}"
		shell
	fi

	# ----------------------------------------------------------------
	# M O U N T   F I L E S Y S T E M S

	# * Ideally, the root filesystem would be mounted like this:
	#
	#     zpool import -R "${rootmnt}" -N "${ZFS_RPOOL}"
	#     zfs mount -o mountpoint=/ "${ZFS_BOOTFS}"
	#
	#   but the MOUNTPOINT prefix is preserved on descendent filesystem
	#   after the pivot into the regular root, which later breaks things
	#   like `zfs mount -a` and the /proc/self/mounts refresh.
	#
	# * Mount additional filesystems required
	#   Such as /usr, /var, /usr/local etc.
	#   NOTE: Mounted in the order specified in the
	#         ZFS_INITRD_ADDITIONAL_DATASETS variable so take care!

	# Go through the complete list (recursively) of all filesystems below
	# the real root dataset
	# As in, nested filesystems:
	#    pool/root
	#    pool/root/usr
	#    pool/root/var
	#    [etc]
	filesystems="$("${ZFS}" list -oname -tfilesystem -H -r "${ZFS_BOOTFS}")"
	OLD_IFS="${IFS}" ; IFS="
"
	for fs in ${filesystems}
	do
		IFS="${OLD_IFS}" mount_fs "${fs}"
	done
	IFS="${OLD_IFS}"

	# Mount any extra filesystems specified in `/etc/default/zfs`.
	# This should only be datasets *not* located nested below the root
	# filesystem, *and* that are part of the operating system.
	# I.e., /home isn't part of the OS, it will be mounted automatically
	# later in the boot process.
	for fs in ${ZFS_INITRD_ADDITIONAL_DATASETS}
	do
		mount_fs "${fs}"
	done

	touch /run/zfs_unlock_complete
	if [ -e /run/zfs_unlock_complete_notify ]
	then
		# shellcheck disable=SC2034
		read -r zfs_unlock_complete_notify < /run/zfs_unlock_complete_notify
	fi

	# ------------
	# Debugging information
	if [ -n "${ZFS_DEBUG}" ]
	then
		#exec 2>&1-

		echo "DEBUG: imported pools:"
		"${ZPOOL}" list -H
		echo

		echo "DEBUG: mounted ZFS filesystems:"
		mount | grep zfs
		echo

		echo "=> waiting for ENTER before continuing because of 'zfsdebug=1'. "
		printf "%s" "   'c' for shell, 'r' for reboot, 'ENTER' to continue. "
		read -r b

		[ "${b}" = "c" ] && /bin/sh
		[ "${b}" = "r" ] && reboot -f

		set +x
	fi

	# ------------
	# Run local bottom script
	if command -v run_scripts > /dev/null 2>&1
	then
		if [ -f "/scripts/local-bottom" ] || [ -d "/scripts/local-bottom" ]
		then
			[ "${quiet}" != "y" ] && \
			    zfs_log_begin_msg "Running /scripts/local-bottom"
			run_scripts /scripts/local-bottom
			[ "${quiet}" != "y" ] && zfs_log_end_msg
		fi
	fi
}