启动elasticsearch的时候报了如下错误：
Starting elasticsearch: Exception in thread "main" : Could not load plugin descriptor for existing plugin []. Was the plugin built before 2.0?
Likely root cause: : /data/esplugins//: Not a directory
at (:91)
at (:102)
at (:107)
at (:214)
at (:361)
at (:407)
at (:384)
at (:152)
at (:87)
at (:378)
at .<init>(:128)
at .<init>(:158)
at .<init>(:140)
at (:143)
at (:178)
at (:270)
at (:35)
Refer to the log for complete error details.
[FAILED]
解决方法：
从报错信息第二行可以看出data/esplugins//: Not a directory，说明没找到这个文件。cd到data/esplugins/下，看到有两个文件，一个是之前下载的，一个是解压完的ik，系统将当成了需要的文件了，但这并不是一个目录，所以把删掉，让系统能够找到ik就可以了。