安装 opennebula 5.6.1 后，在 CentOS 7 上使用（MySQL 数据库选项）的文档，它没有启动，这是问题所在：
# systemctl start opennebula
Job for opennebula.service failed because the control process exited with error code. See "systemctl status opennebula.service" and "journalctl -xe" for details.
# journalctl -xe -u opennebula.service
-- Unit opennebula.service has begun starting up.
Sep 29 20:31:12 snappmarket_01 oned[29854]: Error while parsing configuration file:
Sep 29 20:31:12 snappmarket_01 systemd[1]: opennebula.service: main process exited, code=exited, status=255/n/a
Sep 29 20:31:12 snappmarket_01 follower_cleanup[29857]: /usr/share/one/follower_cleanup:9:in `read': No such file or directory - /var/lib/one/config (Errno::ENOENT)
Sep 29 20:31:12 snappmarket_01 follower_cleanup[29857]: from /usr/share/one/follower_cleanup:9:in `<main>'
Sep 29 20:31:12 snappmarket_01 systemd[1]: opennebula.service: control process exited, code=exited status=1
Sep 29 20:31:12 snappmarket_01 systemd[1]: Failed to start OpenNebula Cloud Controller Daemon.
-- Subject: Unit opennebula.service has failed
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit opennebula.service has failed.
--
-- The result is failed.