elasticsearch 启动错误

**系统版本**
```shell
uname -a
Linux Lserv-54 2.6.32-431.11.2.el6.x86_64 #1 SMP Tue Mar 25 19:59:55 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
cat /etc/redhat-release 
CentOS release 6.5 (Final)
```

**java版本**
```shell
java -version
openjdk version "1.8.0_65-debug"
OpenJDK Runtime Environment (build 1.8.0_65-debug-b17)
OpenJDK 64-Bit Server VM (build 25.65-b01-debug, mixed mode)
```

**使用root启动elasticsearch错误如下：**
elasticsearch 版本 2.1.0
```shell
bin/elasticsearch
Exception in thread "main" java.lang.RuntimeException: don't run elasticsearch as root.
    at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:93)
    at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:144)
    at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:285)
    at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:35)
Refer to the log for complete error details.
```


这个是什么原因呢