mysql: systemd support

Service startup follows sysv initscript and includes db init.

[Thomas: use a relative symlink rather than an absolute symlink.]

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

package/mysql/mysql.mk

@@ -103,6 +103,14 @@ define MYSQL_INSTALL_INIT_SYSV
 		$(TARGET_DIR)/etc/init.d/S97mysqld
 endef
 
+define MYSQL_INSTALL_INIT_SYSTEMD
+	$(INSTALL) -D -m 644 package/mysql/mysqld.service \
+		$(TARGET_DIR)/usr/lib/systemd/system/mysqld.service
+	mkdir -p $(TARGET_DIR)/etc/systemd/system/multi-user.target.wants
+	ln -sf ../../../../usr/lib/systemd/system/mysqld.service \
+		$(TARGET_DIR)/etc/systemd/system/multi-user.target.wants/mysqld.service
+endef
+
 else
 MYSQL_CONF_OPTS += \
 	--without-server

package/mysql/mysqld.service

@@ -0,0 +1,10 @@
+[Unit]
+Description=MySQL database server
+
+[Service]
+ExecStartPre=/bin/sh -c 'test -d /var/mysql/mysql || mysql_install_db --user=mysql --ldata=/var/mysql'
+ExecStart=/usr/bin/mysqld_safe
+Restart=always
+
+[Install]
+WantedBy=multi-user.target