I tried copying files from my local disk to hdfs . At first it gave SafeModeException. While searching for solution I read that the problem does not appear if one executes same command again. So I tried again and it didn't gave exception.
hduser@saket:/usr/local/hadoop$ bin/hadoop dfs -copyFromLocal /tmp/gutenberg/ /user/hduser/gutenberg copyFromLocal: org.apache.hadoop.hdfs.server.namenode.SafeModeException: Cannot create directory /user/hduser/gutenberg. Name node is in safe mode. hduser@saket:/usr/local/hadoop$ bin/hadoop dfs -copyFromLocal /tmp/gutenberg/ /user/hduser/gutenberg
Why is this happening?. Should I keep safemode off by using this code?
hadoop dfs -safemode leave
NameNode is in safemode until configured percent of blocks reported to be online by the data nodes. It can be configured by parameter dfs.namenode.safemode.threshold-pct in the hdfs-site.xml
For small / development clusters, where you have very few blocks - it makes sense to make this parameter lower then its default 0.9999f value. Otherwise 1 missing block can lead to system to hang in safemode.
Go to the hadoop path into bin(in my system /usr/local/hadoop/bin/),
cd /usr/local/hadoop/bin/
Check there is a file hadoop,
hadoopuser@arul-PC:/usr/local/hadoop/bin$ ls
the o/p will be,
hadoop hadoop-daemons.sh start-all.sh start-jobhistoryserver.sh stop-balancer.sh stop-mapred.sh hadoop-config.sh rcc start-balancer.sh start-mapred.sh stop-dfs.sh task-controller hadoop-daemon.sh slaves.sh start-dfs.sh stop-all.sh stop-jobhistoryserver.sh
Then you have to off safe mode by using command ./hadoop dfsadmin -safemode leave,
hadoopuser@arul-PC:/usr/local/hadoop/bin$ ./hadoop dfsadmin -safemode leave
you will get response as,
Safe mode is OFF
Note: I created Hadoop user with the name of hadoopuser.
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