SafeModeException : Name node is in safe mode

Question

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

What was the time difference between executing the commands? It takes a few moments for all the data nodes to come online when you first start up HDFS services. — Chris White, Dec 05 '12 at 19:14
FYI, the command to leave safemode in my version of hadoop is: `hadoop dfsadmin -safemode leave`. — Vlad the Impala, Mar 27 '13 at 14:42
[Check this](http://unmeshasreeveni.blogspot.in/2014/04/name-node-is-in-safe-mode-how-to-leave.html) — USB, Apr 23 '14 at 08:56
the correct command to leave safe mode is `hdfs dfsadmin -safemode leave` — Bakhshi, Nov 15 '16 at 02:06

score 18 · Answer 1 · edited Feb 03 '15 at 06:06

18

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.

edited Feb 03 '15 at 06:06

AdrieanKhisbe

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answered Dec 06 '12 at 07:54

David Gruzman

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While cluster in the safe mode you can read from HDFS, but you cannot write to HDFS. – Yevgen Yampolskiy Dec 06 '12 at 11:20

score 15 · Answer 2 · answered Jul 09 '14 at 08:49

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.

SafeModeException : Name node is in safe mode

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