1. 参考https://hadoop.apache.org/docs/r2.10.2/hadoop-project-dist/hadoop-hdfs/HdfsRollingUpgrade.html
2. 软件准备
1. #新版本准备
   wget https://archive.apache.org/dist/hadoop/common/hadoop-2.10.2/hadoop-2.10.2.tar.gz
   tar -zxvf hadoop-2.10.2.tar.gz -C ../program/
   cp ${HADOOP_HOME}/etc/hadoop/*-site.xml ${DIR}/hadoop-2.10.2/etc/hadoop/
   cp ${HADOOP_HOME}/etc/hadoop/slaves ${DIR}/hadoop-2.10.2/etc/hadoop/
   #拷贝到其他机器
   scp -r ${ip}:${DIR}/hadoop-2.10.2 ${DIR}/hadoop-2.10.2
3. 准备滚动升级
1. 运行“ hdfs dfsadmin -rollingUpgrade prepare ”来创建用于回滚的 fsimage。

运行“ hdfs dfsadmin -rollingUpgrade query ”来检查回滚映像的状态。等待并重新运行该命令，直到显示“ Proceed with rolling upgrade ”消息。

1. 升级主备神经网络
1. 关闭并升级NN2。（如果DN和NN在一台机子上面DN也要关闭，因为要改环境变量）
   ${HADOOP_HOME}/sbin/hadoop-daemon.sh stop namenode
2. 使用“ -rollingUpgrade started ”选项将NN2作为备用启动。
   $HADOOP_HOME/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start namenode -rollingUpgrade started
3. 从NN1故障转移到NN2 ，以便NN2变为活动状态，NN1变为备用状态。
   hdfs haadmin -failover nn2 nn1
4. 关闭并升级NN1。
   ${HADOOP_HOME}/sbin/hadoop-daemon.sh stop namenode 
   使用“ -rollingUpgrade started ”选项将NN1作为备用启动。
   $HADOOP_HOME/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start namenode -rollingUpgrade started
2. 注意点
1. 启动前要切换HADOOP_HOME
2. vim ~/.bash_profile
   export HADOOP_HOME=${DIR}/hadoop-2.10.1
   改成
   export HADOOP_HOME=${DIR}/hadoop-2.10.2
   source ~/.bash_profile
3. 如果遇到no namenode to stop
1. 修改HADOOP_PID_DIR配置
1. mkdir -p ~/hadoop-data/pids
   vim ${HADOOP_HOME}/etc/hadoop/hadoop-env.sh，更改HADOOP_PID_DIR的值
   export HADOOP_PID_DIR=~/hadoop-data/pids
   vim ${HADOOP_HOME}/etc/hadoop/hdfs-site.xml
   dfs.ha.automatic-failover.enabled改成dfs.ha.automatic-failover.enabled.${nameservice的id}
2. 用jps查看现有的hadoop进程，并且kill掉

jps | grep   -E ' NameNode|NodeManager|DataNode|JobHistoryServer|Jps|JournalNode' | awk '{print $1}' | xargs kill

jps | grep   -E ' NodeManager|JournalNode' | awk '{print $1}' | xargs kill

1. 重新启动原来的hadoop程序

#Start the HDFS NameNode with the following command on the designated node as hdfs:
$HADOOP_HOME/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script hdfs start namenode -rollingUpgrade started

#Start a HDFS DataNode with the following command on each designated node as hdfs:
$HADOOP_HOME/sbin/hadoop-daemons.sh --config $HADOOP_CONF_DIR --script hdfs start datanode

#If etc/hadoop/slaves and ssh trusted access is configured (see Single Node Setup), all of the HDFS processes can be started with a utility script. As hdfs:
# $HADOOP_HOME/sbin/start-dfs.sh

#Start the YARN with the following command, run on the designated ResourceManager as yarn:
$HADOOP_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start resourcemanager

#Run a script to start a NodeManager on each designated host as yarn:
$HADOOP_HOME/sbin/yarn-daemons.sh --config $HADOOP_CONF_DIR start nodemanager

#Start a standalone WebAppProxy server. Run on the WebAppProxy server as yarn. If multiple servers are used with load balancing it should be run on each of them:
$HADOOP_HOME/sbin/yarn-daemon.sh --config $HADOOP_CONF_DIR start proxyserver

#If etc/hadoop/slaves and ssh trusted access is configured (see Single Node Setup), all of the YARN processes can be started with a utility script. As yarn:
# $HADOOP_HOME/sbin/start-yarn.sh

#Start the MapReduce JobHistory Server with the following command, run on the designated server as mapred:
$HADOOP_HOME/sbin/mr-jobhistory-daemon.sh --config $HADOOP_CONF_DIR start historyserver

#查看集群状态
hdfs haadmin -getAllServiceState

1. 如果两个NN都是standby，就要强制设置主节点
1. hdfs haadmin -transitionToActive --forcemanual nn1
   #${HADOOP_HOME}/bin/hdfs zkfc -formatZK
1. 升级DN
1. 选择一小部分数据节点（例如特定机架下的所有数据节点）。
1. 运行“ hdfs dfsadmin -shutdownDatanode <DATANODE_HOST:IPC_PORT> upgrade ”以关闭所选数据节点之一。
   运行“ hdfs dfsadmin -getDatanodeInfo <DATANODE_HOST:IPC_PORT> ”检查并等待数据节点关闭。
   升级并重启数据节点。
   $HADOOP_HOME/sbin/hadoop-daemons.sh --config $HADOOP_CONF_DIR --script hdfs start datanode
   对子集中所有选定的数据节点并行执行上述步骤。
2. 重复上述步骤，直到集群中的所有datanode都升级完毕。
2. 完成滚动升级
1. 运行“ hdfs dfsadmin -rollingUpgrade finalize ”以完成滚动升级。
3. 启动hive的元数据$HIVE_HOME/bin/hive --service metastore &