Systemd configuration fixes

* Disable zfs-import-scan.service by default.  This ensures that
pools will not be automatically imported unless they appear in
the cache file.  When this service is explicitly enabled pools
will be imported with the "cachefile=none" property set.  This
prevents the creation of, or update to, an existing cache file.

    $ systemctl list-unit-files | grep zfs
    zfs-import-cache.service                  enabled
    zfs-import-scan.service                   disabled
    zfs-mount.service                         enabled
    zfs-share.service                         enabled
    zfs-zed.service                           enabled
    zfs.target                                enabled

* Change services to dynamic from static by adding an [Install]
section and adding 'WantedBy' tags in favor of 'Requires' tags.
This allows for easier customization of the boot behavior.

* Start the zfs-import-cache.service after the root pivot so
the cache file is available in the standard location.

* Start the zfs-mount.service after the systemd-remount-fs.service
to ensure the root fs is writeable and the ZFS filesystems can
create their mount points.

* Change the default behavior to only load the ZFS kernel modules
in zfs-import-*.service or when blkid(8) detects a pool.  Users
who wish to unconditionally load the kernel modules must uncomment
the list of modules in /lib/modules-load.d/zfs.conf.

Reviewed-by: Richard Laager <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #4325
Closes #4496
Closes #4658
Closes #4699

8 files changed, 29 insertions, 11 deletions

diff --git a/etc/modules-load.d/zfs.conf.in b/etc/modules-load.d/zfs.conf.in
index 73304bc2c..8b41baa30 100644
--- a/etc/modules-load.d/zfs.conf.in
+++ b/etc/modules-load.d/zfs.conf.in
@@ -1 +1,3 @@
-zfs
+# Always load kernel modules at boot.  The default behavior is to load the
+# kernel modules in the zfs-import-*.service or when blkid(8) detects a pool.
+#zfs
diff --git a/etc/systemd/system/50-zfs.preset.in b/etc/systemd/system/50-zfs.preset.in
index 4efdd7200..4d82778e3 100644
--- a/etc/systemd/system/50-zfs.preset.in
+++ b/etc/systemd/system/50-zfs.preset.in
@@ -1,2 +1,7 @@
 # ZFS is enabled by default
-enable zfs.*
+enable zfs-import-cache.service
+disable zfs-import-scan.service
+enable zfs-mount.service
+enable zfs-share.service
+enable zfs-zed.service
+enable zfs.target
diff --git a/etc/systemd/system/zfs-import-cache.service.in b/etc/systemd/system/zfs-import-cache.service.in
index a567b3095..02184a602 100644
--- a/etc/systemd/system/zfs-import-cache.service.in
+++ b/etc/systemd/system/zfs-import-cache.service.in
@@ -4,6 +4,7 @@ DefaultDependencies=no
 Requires=systemd-udev-settle.service
 After=systemd-udev-settle.service
 After=cryptsetup.target
+After=systemd-remount-fs.service
 Before=dracut-mount.service
 ConditionPathExists=@sysconfdir@/zfs/zpool.cache
 
@@ -12,3 +13,7 @@ Type=oneshot
 RemainAfterExit=yes
 ExecStartPre=/sbin/modprobe zfs
 ExecStart=@sbindir@/zpool import -c @sysconfdir@/zfs/zpool.cache -aN
+
+[Install]
+WantedBy=zfs-mount.service
+WantedBy=zfs.target
diff --git a/etc/systemd/system/zfs-import-scan.service.in b/etc/systemd/system/zfs-import-scan.service.in
index cb3c2a7bd..625f3a955 100644
--- a/etc/systemd/system/zfs-import-scan.service.in
+++ b/etc/systemd/system/zfs-import-scan.service.in
@@ -11,4 +11,8 @@ ConditionPathExists=!@sysconfdir@/zfs/zpool.cache
 Type=oneshot
 RemainAfterExit=yes
 ExecStartPre=/sbin/modprobe zfs
-ExecStart=@sbindir@/zpool import -d /dev/disk/by-id -aN
+ExecStart=@sbindir@/zpool import -aN -o cachefile=none
+
+[Install]
+WantedBy=zfs-mount.service
+WantedBy=zfs.target
diff --git a/etc/systemd/system/zfs-mount.service.in b/etc/systemd/system/zfs-mount.service.in
index f1056af31..0664fd9e7 100644
--- a/etc/systemd/system/zfs-mount.service.in
+++ b/etc/systemd/system/zfs-mount.service.in
@@ -1,15 +1,17 @@
 [Unit]
 Description=Mount ZFS filesystems
 DefaultDependencies=no
-Wants=zfs-import-cache.service
-Wants=zfs-import-scan.service
-Requires=systemd-udev-settle.service
 After=systemd-udev-settle.service
 After=zfs-import-cache.service
 After=zfs-import-scan.service
+After=systemd-remount-fs.service
 Before=local-fs.target
 
 [Service]
 Type=oneshot
 RemainAfterExit=yes
 ExecStart=@sbindir@/zfs mount -a
+
+[Install]
+WantedBy=zfs-share.service
+WantedBy=zfs.target
diff --git a/etc/systemd/system/zfs-share.service.in b/etc/systemd/system/zfs-share.service.in
index 1230320e3..688731ea3 100644
--- a/etc/systemd/system/zfs-share.service.in
+++ b/etc/systemd/system/zfs-share.service.in
@@ -3,12 +3,14 @@ Description=ZFS file system shares
 After=nfs-server.service nfs-kernel-server.service
 After=smb.service
 After=zfs-mount.service
-Requires=zfs-mount.service
 PartOf=nfs-server.service nfs-kernel-server.service
 PartOf=smb.service
 
 [Service]
 Type=oneshot
 RemainAfterExit=yes
-ExecStartPre=-@bindir@/rm /etc/dfs/sharetab
+ExecStartPre=-@bindir@/rm -f /etc/dfs/sharetab
 ExecStart=@sbindir@/zfs share -a
+
+[Install]
+WantedBy=zfs.target
diff --git a/etc/systemd/system/zfs-zed.service.in b/etc/systemd/system/zfs-zed.service.in
index 4d4c9d841..e3dec3dca 100644
--- a/etc/systemd/system/zfs-zed.service.in
+++ b/etc/systemd/system/zfs-zed.service.in
@@ -10,3 +10,4 @@ Restart=on-abort
 
 [Install]
 Alias=zed.service
+WantedBy=zfs.target
diff --git a/etc/systemd/system/zfs.target.in b/etc/systemd/system/zfs.target.in
index ce110e573..4699463b0 100644
--- a/etc/systemd/system/zfs.target.in
+++ b/etc/systemd/system/zfs.target.in
@@ -1,8 +1,5 @@
 [Unit]
 Description=ZFS startup target
-Requires=zfs-mount.service
-Requires=zfs-share.service
-Wants=zfs-zed.service
 
 [Install]
 WantedBy=multi-user.target