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.\" Copyright 2018 Antonio Russo <antonio.e.russo@gmail.com>
.\" Copyright 2019 Kjeld Schouten-Lebbing <kjeld@schouten-lebbing.nl>
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.Dd May 31, 2021
.Dt ZFS-MOUNT-GENERATOR 8
.Os OpenZFS
.
.Sh NAME
.Nm zfs-mount-generator
.Nd generate systemd mount units for ZFS filesystems
.Sh SYNOPSIS
.Pa /lib/systemd/system-generators/zfs-mount-generator
.
.Sh DESCRIPTION
.Nm
is a
.Xr systemd.generator 7
that generates native
.Xr systemd.mount 5
units for configured ZFS datasets.
.
.Ss Properties
.Bl -tag -compact -width "org.openzfs.systemd:required-by=unit[ unit]…"
.It Sy mountpoint Ns =
.No Skipped if Sy legacy No or Sy none .
.
.It Sy canmount Ns =
.No Skipped if Sy off .
.No Skipped if only Sy noauto
datasets exist for a given mountpoint and there's more than one.
.No Datasets with Sy yes No take precedence over ones with Sy noauto No for the same mountpoint .
.No Sets logical Em noauto No flag if Sy noauto .
Encryption roots always generate
.Sy zfs-load-key@ Ns Ar root Ns Sy .service ,
even if
.Sy off .
.
.It Sy atime Ns = , Sy relatime Ns = , Sy devices Ns = , Sy exec Ns = , Sy readonly Ns = , Sy setuid Ns = , Sy nbmand Ns =
Used to generate mount options equivalent to
.Nm zfs Cm mount .
.
.It Sy encroot Ns = , Sy keylocation Ns =
If the dataset is an encryption root, its mount unit will bind to
.Sy zfs-load-key@ Ns Ar root Ns Sy .service ,
with additional dependencies as follows:
.Bl -tag -compact -offset Ds -width "keylocation=https://URL (et al.)"
.It Sy keylocation Ns = Ns Sy prompt
None, uses
.Xr systemd-ask-password 1
.It Sy keylocation Ns = Ns Sy https:// Ns Ar URL Pq et al.\&
.Sy Wants Ns = , Sy After Ns = : Pa network-online.target
.It Sy keylocation Ns = Ns Sy file:// Ns < Ns Ar path Ns >
.Sy RequiresMountsFor Ns = Ns Ar path
.El
.
The service also uses the same
.Sy Wants Ns = ,
.Sy After Ns = ,
.Sy Requires Ns = , No and
.Sy RequiresMountsFor Ns = ,
as the mount unit.
.
.It Sy org.openzfs.systemd:requires Ns = Ns Pa path Ns Oo " " Ns Pa path Oc Ns …
.No Sets Sy Requires Ns = for the mount- and key-loading unit.
.
.It Sy org.openzfs.systemd:requires-mounts-for Ns = Ns Pa path Ns Oo " " Ns Pa path Oc Ns …
.No Sets Sy RequiresMountsFor Ns = for the mount- and key-loading unit.
.
.It Sy org.openzfs.systemd:before Ns = Ns Pa unit Ns Oo " " Ns Pa unit Oc Ns …
.No Sets Sy Before Ns = for the mount unit.
.
.It Sy org.openzfs.systemd:after Ns = Ns Pa unit Ns Oo " " Ns Pa unit Oc Ns …
.No Sets Sy After Ns = for the mount unit.
.
.It Sy org.openzfs.systemd:wanted-by Ns = Ns Pa unit Ns Oo " " Ns Pa unit Oc Ns …
.No Sets logical Em noauto No flag (see below) .
.No If not Sy none , No sets Sy WantedBy Ns = for the mount unit.
.It Sy org.openzfs.systemd:required-by Ns = Ns Pa unit Ns Oo " " Ns Pa unit Oc Ns …
.No Sets logical Em noauto No flag (see below) .
.No If not Sy none , No sets Sy RequiredBy Ns = for the mount unit.
.
.It Sy org.openzfs.systemd:nofail Ns = Ns (unset) Ns | Ns Sy on Ns | Ns Sy off
Waxes or wanes strength of default reverse dependencies of the mount unit, see
below.
.
.It Sy org.openzfs.systemd:ignore Ns = Ns Sy on Ns | Ns Sy off
.No Skip if Sy on .
.No Defaults to Sy off .
.El
.
.Ss Unit Ordering And Dependencies
Additionally, unless the pool the dataset resides on
is imported at generation time, both units gain
.Sy Wants Ns = Ns Pa zfs-import.target
and
.Sy After Ns = Ns Pa zfs-import.target .
.Pp
Additionally, unless the logical
.Em noauto
flag is set, the mount unit gains a reverse-dependency for
.Pa local-fs.target
of strength
.Bl -tag -compact -offset Ds -width "(unset)"
.It (unset)
.Sy WantedBy Ns = No + Sy Before Ns =
.It Sy on
.Sy WantedBy Ns =
.It Sy off
.Sy RequiredBy Ns = No + Sy Before Ns =
.El
.
.Ss Cache File
Because ZFS pools may not be available very early in the boot process,
information on ZFS mountpoints must be stored separately.
The output of
.Dl Nm zfs Cm list Fl Ho Ar name , Ns Aq every property above in order
for datasets that should be mounted by systemd should be kept at
.Pa /etc/zfs/zfs-list.cache/ Ns Ar poolname ,
and, if writeable, will be kept synchronized for the entire pool by the
.Pa history_event-zfs-list-cacher.sh
ZEDLET, if enabled
.Pq see Xr zed 8 .
.
.Sh ENVIRONMENT
If the
.Sy ZFS_DEBUG
environment variable is nonzero
.Pq or unset and Pa /proc/cmdline No contains Qq Sy debug ,
print summary accounting information at the end.
.
.Sh EXAMPLES
To begin, enable tracking for the pool:
.Dl # Nm touch Pa /etc/zfs/zfs-list.cache/ Ns Ar poolname
Then enable the tracking ZEDLET:
.Dl # Nm ln Fl s Pa /usr/lib/zfs-linux/zed.d/history_event-zfs-list-cacher.sh /etc/zfs/zed.d
.Dl # Nm systemctl Cm enable Pa zfs-zed.service
.Dl # Nm systemctl Cm restart Pa zfs-zed.service
.Pp
If no history event is in the queue,
inject one to ensure the ZEDLET runs to refresh the cache file
by setting a monitored property somewhere on the pool:
.Dl # Nm zfs Cm set Sy relatime Ns = Ns Sy off Ar poolname/dset
.Dl # Nm zfs Cm inherit Sy relatime Ar poolname/dset
.Pp
To test the generator output:
.Dl $ Nm mkdir Pa /tmp/zfs-mount-generator
.Dl $ Nm /lib/systemd/system-generators/zfs-mount-generator Pa /tmp/zfs-mount-generator
.
If the generated units are satisfactory, instruct
.Nm systemd
to re-run all generators:
.Dl # Nm systemctl daemon-reload
.
.Sh SEE ALSO
.Xr systemd.mount 5 ,
.Xr systemd.target 5 ,
.Xr zfs 5 ,
.Xr systemd.generator 7 ,
.Xr systemd.special 7 ,
.Xr zed 8 ,
.Xr zpool-events 8