Summary of the problem of Hadoop cluster building process

1.datanode node failed to start
(1) Unable to communicate with slave
Check that the slaves file slave node name is correct
Check if the firewall is off (using the Setup command to turn off the firewall, the iptables-f command sometimes fails, chkconfig iptables on command requires a restart)
Check if/etc/hosts is configured correctly
(2) Clusterid mismatch
The Datanode does not match the Clusterid in Namenode: Clusterid in ~/hadoopdata/dfs/namesecondary/current/version is modified to Namenode.
When we perform file system formatting, a current/version file is saved in the Namenode Data folder (that is, in the configuration file Dfs.name.dir the path to the local system), the Namespaceid is recorded, the formatted Version of Namenode. If we format namenode frequently, the Current/version file that is saved in Datanode (that is, the path to the local system in the configuration file) is just the Namenode ID that you saved when you first formatted it, Therefore, the ID inconsistency between Datanode and Namenode is caused.
2.hbase-1.0.2 started successfully, but cannot access master:60010
Add in Hbase-site.xml
<property>
<name>hbase.master.info.port</name>
<value>60010</value>
</property>
3. Exit Safe Mode-safemode
HDFs dfsadmin--safenode Leave
4.hadoop cluster boot not successful-format multiple times
Close the cluster, delete the Hadoopdata directory, and delete all the log files in the Logs folder under the Hadoop installation directory. Reformat and start the cluster again.
5. Jps,hadoop.hdfs and other commands are not recognized
~/.bash_profile file environment variable configuration error, please check carefully. If the command at the beginning can be identified, restarted, or not recognized after some time, re-source ~/.bash_profile.
6.Hive Installation Error: Terminal initialization failed; Falling back to unsupported
Older versions of JLine exist in the Hadoop directory, replacing Jline-2.12.jar in the hive file with the old version of JLine. Restart the Hadoop cluster and start hive again to resolve the problem.
7. If IP is automatically acquired, the cluster will not start, it may be IP change.