How to avoid host key checking during ansible script execution

During execution of ansible playbook or ansible script on new remote host (which you have not connected via ssh so far) the script might fail with below error

 UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: ----}

To avoid this you can set the environment variable (ANSIBLE_HOST_KEY_CHECKING) to disable host check before ssh during ansible script execution.

 export ANSIBLE_HOST_KEY_CHECKING=False

Now you can execute the ansible script.

HMaster not starting up, error "java.io.IOException: Filesystem closed"

HMaster fails to start with below error

util.FSHDFSUtils: attempt=0 on file=hdfs://krbhdfs/apps/hbase/data/MasterProcWALs/state-00000000000000000001.log after 1ms java.io.IOException: Filesystem closed.

There could be multiple causes of the error. 

If you are willing to loose the data, remove manually the logs under "apps/hbase/MasterProcWALs" and  "apps/hbase/WALs" from HDFS. After doing this start the HMaster service.