启动namenode而不进行格式化

Question

I tried to start namenode using bin/start-all.sh. But, this command doesnt start namenode. I know if I do bin/hadoop namenode -format , namenode will start but in that case, I will lose all my data. Is there a way to start namenode without formatting it?

Answer 1

Your problem might be related to the following:

Hadoop writes its NameNode data in /tmp/hadoop- folder by default which is cleaned after every reboot.

Add following property to conf/hdfs-site.xml

<property>
   <name>dfs.name.dir</name>
   <value><path to your desired folder></value>
</property>

The "dfs.name.dir" property allows you to control where Hadoop writes NameNode metadata.

Answer 2

bin/start-all.sh should start the namenode, as well as the datanodes, the jobtracker and the tasktrackers. So, check the log of the namenode for possible errors.

An alternative way to skip starting the jobtracker and the tasktrackers and just start the namenode (and the datanodes) is by using the command: bin/start-dfs.sh

Actually, bin/start-all.sh is equivalent to using the commands:

bin/start-dfs.sh , which starts the namenode and datanodes and
bin/start-mapred.sh , which starts the jobtracker and the tasktrackers.

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