chrony: systemd support

systemd has its own NTP daemon, which must be disabled before
starting chrony. Possible (but unlikely) conflict with openntpd
is not marked in either package.

Signed-off-by: Alex Suykov <alex.suykov@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/chrony/chrony.mk

@@ -45,4 +45,12 @@ define CHRONY_INSTALL_INIT_SYSV
 	$(INSTALL) -D -m 755 package/chrony/S49chrony $(TARGET_DIR)/etc/init.d/S49chrony
 endef
 
+define CHRONY_INSTALL_INIT_SYSTEMD
+	$(INSTALL) -D -m 644 package/chrony/chrony.service \
+		$(TARGET_DIR)/usr/lib/systemd/system/chrony.service
+	mkdir -p $(TARGET_DIR)/etc/systemd/system/multi-user.target.wants
+	ln -sf /usr/lib/systemd/system/chrony.service \
+		$(TARGET_DIR)/etc/systemd/system/multi-user.target.wants/chrony.service
+endef
+
 $(eval $(generic-package))

package/chrony/chrony.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=Chrony Network Time Daemon
+After=syslog.target network.target
+Conflicts=systemd-timesyncd.service
+
+[Service]
+ExecStart=/usr/bin/chronyd -n
+Restart=always
+
+[Install]
+WantedBy=multi-user.target