sorry, 您的问题后来我给漏掉了,不过很高兴您能自己找到答案。
这个是systemd里配置文件里的一种规避错误的机制,具体在systemd的文档里有官方解释,感兴趣可以看看这一段 https://www.freedesktop.org/software/systemd/man/systemd.exec.html#EnvironmentFile=
The argument passed should be an absolute filename or wildcard expression, optionally prefixed with "-", which indicates that if the file does not exist, it will not be read and no error or warning message is logged. This option may be specified more than once in which case all specified files are read. If the empty string is assigned to this option, the list of file to read is reset, all prior assignments have no effect.