mirror_zfs/etc/systemd/system-generators/zfs-mount-generator.in
Antonio Russo 55d80e651a systemd mount generator and tracking ZEDLET
zfs-mount-generator implements the "systemd generator" protocol,
producing systemd.mount units from the cached outputs of zfs list,
during early boot, integrating with systemd.

Each pool has an indpendent cache of the command

  zfs list -H -oname,mountpoint,canmount -tfilesystem -r $pool

which is kept synchronized by the ZEDLET

  history_event-zfs-list-cacher.sh

Datasets not in the cache will be loaded later in the boot process by
zfs-mount.service, including pools without a cache.

Among other things, this allows for complex mount hierarchies.

Reviewed-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Antonio Russo <antonio.e.russo@gmail.com>
Closes #7329
2018-04-06 14:11:09 -07:00

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#!/bin/sh
# zfs-mount-generator - generates systemd mount units for zfs
# Copyright (c) 2017 Antonio Russo <antonio.e.russo@gmail.com>
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
set -ef
FSLIST="@sysconfdir@/zfs/zfs-list.cache"
[ -d "${FSLIST}" ] || exit 0
do_fail() {
printf 'zfs-mount-generator.sh: %s\n' "$*" > /dev/kmsg
exit 1
}
# see systemd.generator
if [ $# -eq 0 ] ; then
dest_norm="/tmp"
elif [ $# -eq 3 ] ; then
dest_norm="${1}"
else
do_fail "zero or three arguments required"
fi
# For ZFSs marked "auto", a dependency is created for local-fs.target. To
# avoid regressions, this dependency is reduced to "wants" rather than
# "requires". **THIS MAY CHANGE**
req_dir="${dest_norm}/local-fs.target.wants/"
mkdir -p "${req_dir}"
# All needed information about each ZFS is available from
# zfs list -H -t filesystem -oname,mountpoint,canmount
# cached in $FSLIST, and each line is processed by the following function:
process_line() {
# Check for canmount=off .
if [ "${3}" = "off" ] ; then
return
elif [ "${3}" = "noauto" ] ; then
# Don't let a noauto marked mountpoint block an "auto" market mountpoint
return
elif [ "${3}" = "on" ] ; then
: # This is OK
else
do_fail "invalid canmount"
fi
# Check for legacy and blank mountpoints.
if [ "${2}" = "legacy" ] ; then
return
elif [ "${2}" = "none" ] ; then
return
elif [ "${2%"${2#?}"}" != "/" ] ; then
do_fail "invalid mountpoint $*"
fi
# Escape the mountpoint per systemd policy.
mountfile="$(systemd-escape "${2#?}").mount"
# If the mountpoint has already been created, give it precedence.
if [ -e "${dest_norm}/${mountfile}" ] ; then
printf 'zfs-mount-generator.sh: %s.mount already exists\n' "${2}" \
>/dev/kmsg
return
fi
# By ordering before zfs-mount.service, we avoid race conditions.
cat > "${dest_norm}/${mountfile}" << EOF
# Automatically generated by zfs-mount-generator
[Unit]
SourcePath=${FSLIST}/${cachefile}
Documentation=man:zfs-mount-generator(8)
Before=local-fs.target zfs-mount.service
After=zfs-import.target
Wants=zfs-import.target
[Mount]
Where=${2}
What=${1}
Type=zfs
Options=zfsutil,auto
EOF
# Finally, create the appropriate dependencies based on the ZFS properties.
[ "$3" = "on" ] & ln -s "../${mountfile}" "${req_dir}"
}
# Feed each line into process_line
for cachefile in $(ls "${FSLIST}") ; do
while read -r fs ; do
process_line $fs
done < "${FSLIST}/${cachefile}"
done