ubuntu apache2启动遇到未知错误

Question

环境为ubuntu18.0.4，启动apache2，启动失败，在error log中也没有错误提示。请问怎么解决？x'x

error log 如下：

3月 19 17:58:56 hannah-virtual-machine systemd[1]: Starting Cleanup of Temporary Directories...
-- Subject: systemd-tmpfiles-clean.service 单元已开始启动
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- systemd-tmpfiles-clean.service 单元已开始启动。
3月 19 17:58:56 hannah-virtual-machine systemd[1]: Started Cleanup of Temporary Directories.
-- Subject: systemd-tmpfiles-clean.service 单元已结束启动
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- systemd-tmpfiles-clean.service 单元已结束启动。
-- 
-- 启动结果为“RESULT”。
3月 19 17:59:36 hannah-virtual-machine polkitd(authority=local)[683]: Registered Authentication Agent for unix-process:2624:95107 (sys
3月 19 17:59:41 hannah-virtual-machine polkitd(authority=local)[683]: Operator of unix-session:4 successfully authenticated as unix-us
3月 19 17:59:41 hannah-virtual-machine systemd[1]: Starting The Apache HTTP Server...
-- Subject: apache2.service 单元已开始启动
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- apache2.service 单元已开始启动。
3月 19 17:59:41 hannah-virtual-machine apachectl[2634]: Action 'start' failed.
3月 19 17:59:41 hannah-virtual-machine apachectl[2634]: The Apache error log may have more information.
3月 19 17:59:41 hannah-virtual-machine systemd[1]: apache2.service: Control process exited, code=exited status=1
3月 19 17:59:41 hannah-virtual-machine systemd[1]: apache2.service: Failed with result 'exit-code'.
3月 19 17:59:41 hannah-virtual-machine systemd[1]: Failed to start The Apache HTTP Server.
-- Subject: apache2.service 单元已失败
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- 
-- apache2.service 单元已失败。
-- 
-- 结果为“RESULT”。
3月 19 17:59:41 hannah-virtual-machine polkitd(authority=local)[683]: Unregistered Authentication Agent for unix-process:2624:95107 (s
lines 1725-1759/1759 (END)