上传MapReduce的jar包时
1、Exception in thread “main” org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /tmp/hadoop-yarn/staging/root/.staging/job_1625723817019_0003/job.jar could only be replicated to 0 nodes instead of minReplication (=1). There are 2 datanode(s) running and 2 node(s) are excluded in this operation.、
解决办法，每台都要关闭
systemctl stop firewalld.service #停止firewall
systemctl disable firewalld.service #禁止firewall开机启动
firewall-cmd --state #查看默认防火墙状态（关闭后显示notrunning，开启后显示running）
2、Exception in thread “main” org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.server.namenode.SafeModeException): Cannot delete /tmp/hadoop-yarn/staging/root/.staging/job_1625792478226_0001. Name node is in safe mode.The reported blocks 0 needs additional 12 blocks to reach the threshold 0.9990 of total blocks 12.
解决办法
Linux集群中的namenode没有关闭safemode
hadoop dfsadmin -safemode leave/enter（退出/进入安全模式）
