ElasticSearch 2.3.5 throwing InvalidIndexNameException[

Hello,

I have installed es 2.3.5 on two node cluster and am seeing error like below while was trying to shutdown cluster using curl command or when I try to use _cluster command ,it's throwing similar error as below. I have only installed head plug in along wth ES 2.3.5 . Head plugin is also not working from browser

[_shutdown] failed to create
[_shutdown] InvalidIndexNameException[Invalid index name [shutdown], must not start with '']
at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService.validateIndexName(MetaDataCreateIndexService.java:150)
at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService.validate(MetaDataCreateIndexService.java:473)
at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService.access$100(MetaDataCreateIndexService.java:97)
at org.elasticsearch.cluster.metadata.MetaDataCreateIndexService$1.execute(MetaDataCreateIndexService.java:192)
at org.elasticsearch.cluster.ClusterStateUpdateTask.execute(ClusterStateUpdateTask.java:45)
at org.elasticsearch.cluster.service.InternalClusterService.runTasksForExecutor(InternalClusterService.java:468)
at org.elasticsearch.cluster.service.InternalClusterService$UpdateTask.run(InternalClusterService.java:772)
at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:231)
at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:194)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
[2016-08-18 00:14:00,916][WARN ][bootstrap ] unable to install syscall filter: seccomp unavailable: CONFIG_SECCOMP not compiled into kernel, CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER are needed
[2016-08-18 00:14:00,920][WARN ][bootstrap ] Unable to lock JVM Memory: error=12,reason=Cannot allocate memory
[2016-08-18 00:14:00,920][WARN ][bootstrap ] This can result in part of the JVM being swapped out.
[2016-08-18 00:14:00,920][WARN ][bootstrap ] Increase RLIMIT_MEMLOCK, soft limit: 65536, hard limit: 65536
[2016-08-18 00:14:00,920][WARN ][bootstrap ] These can be adjusted by modifying /etc/security/limits.conf, for example:

Any help greatly appreciable.

Thanks,

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