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systemd mount generator
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zfs-mount-generator implements the "systemd generator" protocol,
producing systemd.mount units from the (possibly cached) output
of zfs list during early boot, integrating with systemd.

Among other things, this allows for complex mount hierarchies.

Signed-off-by: Antonio Russo <antonio.e.russo@gmail.com>
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aerusso committed Mar 22, 2018
1 parent 05747ec commit 0eff96e
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Showing 9 changed files with 202 additions and 2 deletions.
8 changes: 7 additions & 1 deletion config/user-systemd.m4
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,11 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
[install systemd module load files into dir [[/usr/lib/modules-load.d]]]),
systemdmoduleloaddir=$withval,systemdmodulesloaddir=/usr/lib/modules-load.d)
AC_ARG_WITH(systemdgeneratordir,
AC_HELP_STRING([--with-systemdgeneratordir=DIR],
[install systemd generators in dir [[/usr/lib/systemd/system-generators]]]),
systemdgeneratordir=$withval,systemdgeneratordir=/usr/lib/systemd/system-generators)
AS_IF([test "x$enable_systemd" = xcheck], [
AS_IF([systemctl --version >/dev/null 2>&1],
[enable_systemd=yes],
Expand All @@ -32,7 +37,7 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
AS_IF([test "x$enable_systemd" = xyes], [
ZFS_INIT_SYSTEMD=systemd
ZFS_MODULE_LOAD=modules-load.d
DEFINE_SYSTEMD='--with systemd --define "_unitdir $(systemdunitdir)" --define "_presetdir $(systemdpresetdir)"'
DEFINE_SYSTEMD='--with systemd --define "_unitdir $(systemdunitdir)" --define "_presetdir $(systemdpresetdir)" --define "_generatordir $(systemdgeneratordir)"'
modulesloaddir=$systemdmodulesloaddir
],[
DEFINE_SYSTEMD='--without systemd'
Expand All @@ -43,5 +48,6 @@ AC_DEFUN([ZFS_AC_CONFIG_USER_SYSTEMD], [
AC_SUBST(DEFINE_SYSTEMD)
AC_SUBST(systemdunitdir)
AC_SUBST(systemdpresetdir)
AC_SUBST(systemdgeneratordir)
AC_SUBST(modulesloaddir)
])
1 change: 1 addition & 0 deletions configure.ac
Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,7 @@ AC_CONFIG_FILES([
etc/zfs/Makefile
etc/systemd/Makefile
etc/systemd/system/Makefile
etc/systemd/system-generators/Makefile
etc/sudoers.d/Makefile
etc/modules-load.d/Makefile
man/Makefile
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2 changes: 1 addition & 1 deletion etc/systemd/Makefile.am
Original file line number Diff line number Diff line change
@@ -1 +1 @@
SUBDIRS = system
SUBDIRS = system system-generators
1 change: 1 addition & 0 deletions etc/systemd/system-generators/.gitignore
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
zfs-mount-generator
15 changes: 15 additions & 0 deletions etc/systemd/system-generators/Makefile.am
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
systemdgenerator_SCRIPTS = \
zfs-mount-generator

EXTRA_DIST = \
$(top_srcdir)/etc/systemd/system-generators/zfs-mount-generator.in

$(systemdgenerator_SCRIPTS): %: %.in
-$(SED) -e 's,@bindir\@,$(bindir),g' \
-e 's,@runstatedir\@,$(runstatedir),g' \
-e 's,@sbindir\@,$(sbindir),g' \
-e 's,@sysconfdir\@,$(sysconfdir),g' \
$< >'$@'

distclean-local::
-$(RM) $(systemdgenerator_SCRIPTS)
130 changes: 130 additions & 0 deletions etc/systemd/system-generators/zfs-mount-generator.in
Original file line number Diff line number Diff line change
@@ -0,0 +1,130 @@
#!/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"

do_fail() {
printf '%s\n' "$*" >&2
exit 1
}

# We don't use dest_late
if [ $# -eq 0 ] ; then
dest_norm="/tmp"
#dest_late="/tmp"
elif [ $# -eq 3 ] ; then
dest_norm="${1}"
#dest_late="${3}"
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
# each line is processed by the following function:

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

# 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

# Escape the mountpoint per systemd policy.
mountfile="${2#?}"
mountfile="$(systemd-escape "${mountfile}").mount"

# If the mountpoint has already been created,
# give it precedence.
[ -e "${dest_norm}/${mountfile}" ] && return

# heredocs may not work in very early boot,
# so we'll use printf instead.
out() {
printf '%s\n' "$*" >> "${dest_norm}/${mountfile}"
}

# dump the mount unit
out "# Automatically generated by zfs-mount-generator"
out ""
out "[Unit]"
[ -n "${SOURCEPATH}" ] && out "${SOURCEPATH}"
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}"

# finally, create the appropriate dependencies based on
# the ZFS properties
[ "$3" = "on" ] & ln -s "../${mountfile}" "${req_dir}"
}

# First, try listing ZFSs directly:
(@sbindir@/zfs list -H -t filesystem -oname,mountpoint,canmount 2>/dev/null ||
true) | while read -r fs ; do
process_line $fs
done

# At the early stage that systemd generators are called,
# pools may not be imported, and the above may fail.

# $FSLIST, if available, is a cache of the output of
# the above command. Process it if it exists.

if [ -r "${FSLIST}" ] ; then
SOURCEPATH="SourcePath=${FSLIST}"
while read -r fs ; do
process_line $fs
done < "${FSLIST}"
fi
1 change: 1 addition & 0 deletions man/man8/Makefile.am
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ dist_man_MANS = \
vdev_id.8 \
zdb.8 \
zfs.8 \
zfs-mount-generator.8 \
zfs-program.8 \
zgenhostid.8 \
zinject.8 \
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45 changes: 45 additions & 0 deletions man/man8/zfs-mount-generator.8
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@@ -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)
1 change: 1 addition & 0 deletions rpm/generic/zfs.spec.in
Original file line number Diff line number Diff line change
Expand Up @@ -337,6 +337,7 @@ systemctl --system daemon-reload >/dev/null || true
/usr/lib/modules-load.d/*
%{_unitdir}/*
%{_presetdir}/*
%{_generatordir}/*
%else
%config(noreplace) %{_sysconfdir}/init.d/*
%config(noreplace) %{_initconfdir}/zfs
Expand Down

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