- Live Nodes show as 0
* Step 1: View the datanode log tail -100 /home/hadoop-2.5.1/logs/hadoop-root-datanode-node2.log
* Abnormal problem: 
* Reason: Repeated formatting. After formatting dfs for the first time, hadoop was started and used, and then the format command (hdfs namenode -format) was re-executed. At this time, the clusterID of the namenode will be regenerated, and the clusterID of the datanode will remain unchanged.
* Solution: Copy the clusterID in the VERSION under name/current to the VERSION under data/current, and overwrite the original clusterID, that is, keep it consistent.
* Restart
参考链接：[https://my.oschina.net/zhongwenhao/blog/603744][3]
2. Reasons and solutions for the failure of eclipse to upload files to Hadoop
Reason : The system does not have permission
Solution: Modify the file vim hadoop/etc/hadoop/hdfs-site.xml
Add configuration:
<property>
<name>dfs.permissions</name>
<value>false</value>
</property>- Hadoop error: could only be replicated to 0 nodes, instead of 1
Reason: Formatting hadoop multiple times leads to inconsistent version information
Solution : Stop all services and reformat
- Stop all services first stop-all.sh
- format hadoop namenode -foramt
- Restart all services start-all.sh
Note, this may cause problem 1! !