執行任務時報以下錯：
Safe mode is ON in r2n03/192.168.0.43:8020
ERROR to execute safemode cmd: get on r1n08/192.168.0.38:8020 , Exception = java.net.ConnectException: Call From r2n03/192.168.0.43 to r1n08:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
2020-03-30 20:32:30,165 INFO util.KerberosUtil: Using principal pattern: HTTP/_HOST
2020-03-30 20:32:31,541 INFO util.KerberosUtil: Using principal pattern: HTTP/_HOST
Save namespace successful for r2n03/192.168.0.43:8020
saveNamespace: Call From r2n03/192.168.0.43 to r1n08:8020 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
手動退出安全模式：
su -s /bin/bash hdfs -c "
export HADOOP_CLIENT_OPTS='-Dtranswarp.maintenance.only.mode=true';
hdfs dfsadmin -safemode leave "