centos6.5 elasticsearch6.0 安装xpack 6.0，
执行 ./bin/elasticsearch -d 查看log 错误如下：

org.elasticsearch.bootstrap.StartupException: java.lang.IllegalStateException: failed to load plugin class [org.elasticsearch.xpack.XPackPlugin]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:134) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:121) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:69) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:134) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:92) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:85) ~[elasticsearch-6.0.0.jar:6.0.0]
Caused by: java.lang.IllegalStateException: failed to load plugin class [org.elasticsearch.xpack.XPackPlugin]
        at org.elasticsearch.plugins.PluginsService.loadPlugin(PluginsService.java:452) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.plugins.PluginsService.loadBundles(PluginsService.java:392) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.plugins.PluginsService.<init>(PluginsService.java:142) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.node.Node.<init>(Node.java:302) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.node.Node.<init>(Node.java:245) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:212) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:212) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:322) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:130) ~[elasticsearch-6.0.0.jar:6.0.0]
        ... 6 more
Caused by: java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:?]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:?]
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:?]
        at java.lang.reflect.Constructor.newInstance(Constructor.java:422) ~[?:1.8.0_73]
        at org.elasticsearch.plugins.PluginsService.loadPlugin(PluginsService.java:443) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.plugins.PluginsService.loadBundles(PluginsService.java:392) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.plugins.PluginsService.<init>(PluginsService.java:142) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.node.Node.<init>(Node.java:302) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.node.Node.<init>(Node.java:245) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:212) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:212) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:322) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:130) ~[elasticsearch-6.0.0.jar:6.0.0]
        ... 6 more
Caused by: java.lang.IllegalArgumentException: the [action.auto_create_index] setting value [.security,.monitoring*,.watches,.triggered_watches,.watcher-history*,.ml*] is too restrictive. disable [action.auto_create_index] or set it to [.security,.security-6]
        at org.elasticsearch.xpack.security.Security.validateAutoCreateIndex(Security.java:814) ~[?:?]
        at org.elasticsearch.xpack.security.Security.<init>(Security.java:256) ~[?:?]
        at org.elasticsearch.xpack.XPackPlugin.<init>(XPackPlugin.java:240) ~[?:?]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:?]
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:?]
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:?]
        at java.lang.reflect.Constructor.newInstance(Constructor.java:422) ~[?:1.8.0_73]
        at org.elasticsearch.plugins.PluginsService.loadPlugin(PluginsService.java:443) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.plugins.PluginsService.loadBundles(PluginsService.java:392) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.plugins.PluginsService.<init>(PluginsService.java:142) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.node.Node.<init>(Node.java:302) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.node.Node.<init>(Node.java:245) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:212) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:212) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:322) ~[elasticsearch-6.0.0.jar:6.0.0]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:130) ~[elasticsearch-6.0.0.jar:6.0.0]
        ... 6 more

解决办法：

允许自动建立x-pack索引，配置文件config/elasticsearch.yml ，新增

action.auto_create_index: .security,.monitoring*,.watches,.triggered_watches,.watcher-history*,.ml*,.security,.security-6