启动或者停止hadoop的时候，信息如下：
Stopping namenodes on [hadoop1 hadoop2] The authenticity of host 'hadoop2 (172.17.0.10)' can't be established. ECDSA key fingerprint is SHA256:2L+Ij0z9q1BkINoGu1JVxIoHKwyeJEZXZIVbll0t9fc. ECDSA key fingerprint is MD5:9f:32:5f:a6:50:11:c6:42:53:5c:12:48:54:96:ba:0f. Are you sure you want to continue connecting (yes/no)? hadoop1: stopping namenode ^Chadoop2: Host key verification failed. The authenticity of host 'hadoop3 (172.17.0.11)' can't be established. ECDSA key fingerprint is SHA256:b6wioHFMQ/54d1Oc8BLOBnPvT1L5Ss8zp2bbSkvPG7w. ECDSA key fingerprint is MD5:d6:2a:51:53:e4:ea:5c:40:9b:8f:87:21:1f:d0:f9:f8. Are you sure you want to continue connecting (yes/no)? The authenticity of host 'hadoop2 (172.17.0.10)' can't be established. ECDSA key fingerprint is SHA256:2L+Ij0z9q1BkINoGu1JVxIoHKwyeJEZXZIVbll0t9fc. ECDSA key fingerprint is MD5:9f:32:5f:a6:50:11:c6:42:53:5c:12:48:54:96:ba:0f. Are you sure you want to continue connecting (yes/no)? hadoop1: no datanode to stop ^Chadoop2: Host key verification failed. hadoop3: Host key verification failed. Stopping journal nodes [hadoop1 hadoop2 hadoop3] The authenticity of host 'hadoop2 (172.17.0.10)' can't be established. ECDSA key fingerprint is SHA256:2L+Ij0z9q1BkINoGu1JVxIoHKwyeJEZXZIVbll0t9fc. ECDSA key fingerprint is MD5:9f:32:5f:a6:50:11:c6:42:53:5c:12:48:54:96:ba:0f. Are you sure you want to continue connecting (yes/no)? The authenticity of host 'hadoop3 (172.17.0.11)' can't be established. ECDSA key fingerprint is SHA256:b6wioHFMQ/54d1Oc8BLOBnPvT1L5Ss8zp2bbSkvPG7w. ECDSA key fingerprint is MD5:d6:2a:51:53:e4:ea:5c:40:9b:8f:87:21:1f:d0:f9:f8. Are you sure you want to continue connecting (yes/no)? hadoop1: stopping journalnode
每次都需要输入yes，对于大集群来说，很尴尬
在hadoop-env.sh添加环境变量，如下：
export HADOOP_SSH_OPTS= "-o StrictHostKeyChecking=no"