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zfs-mount-generator implements the "systemd generator" protocol, producing systemd.mount units from the cached output of zfs list, zfs-list.cache, during early boot, integrating with systemd. zfs-list.cache is kept up-to-date by the zed event script history_event-zfs-list-cacher.sh, which ensures that every listed filesystem's entry in zfs-list.cache is synchronized with the pool state. It is left to the system administrator's judgement which ZFSs should be in this cache. ZFSs not in this cache will be loaded later in the boot process by zfs-mount.service. Among other things, this allows for complex mount hierarchies. Signed-off-by: Antonio Russo <antonio.e.russo@gmail.com>
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| Original file line number | Diff line number | Diff line change |
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| history_event-zfs-list-cacher.sh |
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| #!/bin/sh | ||
| # | ||
| # Track changes to specifically enumerated filesystems for system mounting. | ||
| set -e | ||
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| FSLIST="@sysconfdir@/zfs/zfs-list.cache" | ||
| FSLIST_TMP="@runstatedir@/zfs-list.cache.new" | ||
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| # If it is not writeable, then do not attempt to modify | ||
| [ -w "${FSLIST}" ] || exit 0 | ||
| # If it is empty, abort | ||
| [ "$(wc -l < "${FSLIST}")" -eq 0 ] && exit 0 | ||
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| [ -f "${ZED_ZEDLET_DIR}/zed.rc" ] && . "${ZED_ZEDLET_DIR}/zed.rc" | ||
| . "${ZED_ZEDLET_DIR}/zed-functions.sh" | ||
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| zed_exit_if_ignoring_this_event | ||
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| # We obtain a lock on zfs-list to avoid any simultaneous writes. | ||
| # If we run into trouble, log and drop the lock | ||
| abort_alter() { | ||
| zed_log_msg "Error updating zfs-list.cache!" | ||
| zed_unlock zfs-list | ||
| } | ||
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| case "${ZEVENT_HISTORY_INTERNAL_NAME}" in | ||
| destroy|rename) | ||
| # because the history event only reports the command issued, rather than | ||
| # the affected ZFS, a rename or recursive destroy can affect a child ZFS. | ||
| # Instead of trying to figure out if we're affected, we instead just | ||
| # regenerate the cache *for that pool* on every modification. | ||
| ;; | ||
| set) | ||
| # only act if the mountpoint or canmount setting is altered | ||
| printf '%s' "${ZEVENT_HISTORY_INTERNAL_STR}" | | ||
| grep -q '^\(mountpoint\|canmount\)=' || exit 0 | ||
| ;; | ||
| *) | ||
| # ignore all other events | ||
| exit 0 | ||
| ;; | ||
| esac | ||
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| zed_lock zfs-list | ||
| trap abort_alter EXIT | ||
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| # Get the information for the affected pool | ||
| grep "^${ZEVENT_POOL}[/$(printf '\t')]" "${FSLIST}" | | ||
| grep -o '[^'"$(printf '\t')"'*' | | ||
| xargs @sbindir@/zfs list -H -oname,mountpoint,canmount \ | ||
| >"${FSLIST_TMP}" 2>/dev/null || true | ||
| # Gather the old information for the unaffected pools | ||
| grep -v "^${ZEVENT_POOL}[/$(printf '\t')]" "${FSLIST}" >>"${FSLIST_TMP}" | ||
| # Sort the output so that it is stable | ||
| sort "${FSLIST_TMP}" | ||
| # Don't modify the file if it hasn't changed | ||
| diff -q "${FSLIST_TMP}" "${FSLIST}" || mv "${FSLIST_TMP}" "${FSLIST}" | ||
| rm -f "${FSLIST_TMP}" | ||
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| zed_unlock zfs-list | ||
| trap - EXIT |
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| Original file line number | Diff line number | Diff line change |
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| @@ -1 +1 @@ | ||
| SUBDIRS = system | ||
| SUBDIRS = system system-generators |
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| zfs-mount-generator |
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| systemdgenerator_SCRIPTS = \ | ||
| zfs-mount-generator | ||
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| EXTRA_DIST = \ | ||
| $(top_srcdir)/etc/systemd/system-generators/zfs-mount-generator.in | ||
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| $(systemdgenerator_SCRIPTS): %: %.in | ||
| -$(SED) -e 's,@bindir\@,$(bindir),g' \ | ||
| -e 's,@runstatedir\@,$(runstatedir),g' \ | ||
| -e 's,@sbindir\@,$(sbindir),g' \ | ||
| -e 's,@sysconfdir\@,$(sysconfdir),g' \ | ||
| $< >'$@' | ||
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| distclean-local:: | ||
| -$(RM) $(systemdgenerator_SCRIPTS) |
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| #!/bin/sh | ||
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| # zfs-mount-generator - generates systemd mount units for zfs | ||
| # Copyright (c) 2017 Antonio Russo <antonio.e.russo@gmail.com> | ||
| # | ||
| # Permission is hereby granted, free of charge, to any person obtaining | ||
| # a copy of this software and associated documentation files (the | ||
| # "Software"), to deal in the Software without restriction, including | ||
| # without limitation the rights to use, copy, modify, merge, publish, | ||
| # distribute, sublicense, and/or sell copies of the Software, and to | ||
| # permit persons to whom the Software is furnished to do so, subject to | ||
| # the following conditions: | ||
| # | ||
| # The above copyright notice and this permission notice shall be | ||
| # included in all copies or substantial portions of the Software. | ||
| # | ||
| # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, | ||
| # EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF | ||
| # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND | ||
| # NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE | ||
| # LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION | ||
| # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION | ||
| # WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. | ||
|
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| set -ef | ||
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| FSLIST="@sysconfdir@/zfs/zfs-list.cache" | ||
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| [ -r "${FSLIST}" ] || exit 0 | ||
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| do_fail() { | ||
| printf 'zfs-mount-generator.sh: %s\n' "$*" > /dev/kmsg | ||
| exit 1 | ||
| } | ||
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| # 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 | ||
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| # 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}" | ||
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| # All needed information about each ZFS is available from | ||
| # zfs list -H -t filesystem -oname,mountpoint,canmount | ||
| # cached in $FSLIST, and each line is processed by the following function: | ||
|
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| process_line() { | ||
| # Check for canmount=off . | ||
| if [ "${3}" = "off" ] ; then | ||
| return | ||
| elif [ "${3}" = "on" ] ; then | ||
| auto="auto" | ||
| elif [ "${3}" = "noauto" ] ; then | ||
| auto="noauto" | ||
| else | ||
| do_fail "invalid canmount" | ||
| fi | ||
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| # Check for legacy and blank mountpoints. | ||
| if [ "${2}" = "legacy" ] ; then | ||
| return | ||
| elif [ "${2}" = "none" ] ; then | ||
| return | ||
| elif [ "$(printf '%.1s' "${2}")" != "/" ] ; then | ||
| do_fail "invalid mountpoint $*" | ||
| fi | ||
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| # Escape the mountpoint per systemd policy. | ||
| mountfile="$(systemd-escape "${2#?}").mount" | ||
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| # If the mountpoint has already been created, give it precedence. | ||
| if [ -e "${dest_norm}/${mountfile}" ] ; then | ||
| printf 'zfs-mount-generator.sh: %s.mount already exists\n' "${2}" \ | ||
| >/dev/kmsg | ||
| return | ||
| fi | ||
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| # heredocs may not work in very early boot, so we'll use printf instead. | ||
| out() { | ||
| printf '%s\n' "$*" >> "${dest_norm}/${mountfile}" | ||
| } | ||
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| # dump the mount unit | ||
| out "# Automatically generated by zfs-mount-generator" | ||
| out "" | ||
| out "[Unit]" | ||
| out "SourcePath=${FSLIST}" | ||
| out "Documentation=man:zfs-mount-generator(8)" | ||
| # By ordering before zfs-mount.service, we avoid race conditions. | ||
| out "Before=local-fs.target zfs-mount.service" | ||
| out "After=zfs-import.target" | ||
| out "Wants=zfs-import.target" | ||
| out "" | ||
| out "[Mount]" | ||
| out "Where=${2}" | ||
| out "What=${1}" | ||
| out "Type=zfs" | ||
| out "Options=zfsutil,${auto}" | ||
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| # Finally, create the appropriate dependencies based on the ZFS properties. | ||
| [ "$3" = "on" ] & ln -s "../${mountfile}" "${req_dir}" | ||
| } | ||
|
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| # Feed each line into process_line | ||
| while read -r fs ; do | ||
| process_line $fs | ||
| done < "${FSLIST}" |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,45 @@ | ||
| .TH "ZFS\-MOUNT\-GENERATOR" "8" "ZFS" "zfs-mount-generator" "\"" | ||
| .SH "NAME" | ||
| zfs\-mount\-generator \- generates systemd mount units for zfs | ||
| .SH SYNOPSIS | ||
| .B /lib/systemd/system-generators/zfs\-mount\-generator | ||
| .sp | ||
| .SH DESCRIPTION | ||
| The zfs\-mount\-generator implements the \fBGenerators Specification\fP | ||
| of | ||
| .BR systemd (1), | ||
| and is called during early boot to generate | ||
| .BR systemd.mount (5) | ||
| units for ZFS filesystem. If pools are not imported before | ||
| systemd generators are run, information on ZFS mountpoints should | ||
| be stored: the output of the command | ||
| .PP | ||
| .RS 4 | ||
| zfs list -H -t filesystem -oname,mountpoint,canmount | ||
| .RE | ||
| .PP | ||
| should be kept separate from the pool, at | ||
| .PP | ||
| .RS 4 | ||
| @sysconfdir@/zfs/zfs-list.cache . | ||
| .RE | ||
| .PP | ||
| If this file exists, it will supplement (but not override) information | ||
| available at run-time about the ZFS mount points. Mount ordering and | ||
| dependencies are created for all listed filesystems. If a filesystem has | ||
| .BR canmount=on | ||
| and | ||
| .BR mountpoint , | ||
| the | ||
| .BR auto | ||
| mount option will be set, and a dependency for | ||
| .BR local-fs.target | ||
| on the mount will be created. | ||
| .sp | ||
| .SH SEE ALSO | ||
| .BR zfs (5) | ||
| .BR zpool (5) | ||
| .BR systemd (1) | ||
| .BR systemd.target (5) | ||
| .BR systemd.special (7) | ||
| .BR systemd.mount (7) |
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