SafeModeException：名称节点处于安全模式 [英] SafeModeException : Name node is in safe mode

问题描述

我尝试将文件从本地磁盘复制到 hdfs 。起初它给了 SafeModeException 。在搜索解决方案时，我发现如果再次执行相同的命令，问题不会出现。所以我再次尝试，并没有给出异常。

  hduser @ saket：/ usr / local / hadoop $ bin / hadoop dfs -copyFromLocal / tmp / gutenberg / / user / hduser / gutenberg 
 copyFromLocal：org.apache.hadoop.hdfs.server.namenode.SafeModeException：无法创建目录/ user / hduser / gutenberg。名称节点处于安全模式。 
 hduser @ saket：/ usr / local / hadoop $ bin / hadoop dfs -copyFromLocal / tmp / gutenberg / / user / hduser / gutenberg 
  

为什么会发生这种情况？我应该使用这段代码保持安全模式吗？

  hadoop dfs -safemode leave 
  
         NameNode 位于 safemode 报告数据节点在线的块。它可以通过 hdfs-site.xml  中的参数 dfs.namenode.safemode.threshold-pct  p> 
 
 
对于小块/开发群集，只有很少块的情况下 - 将此参数设置为低于其默认值 0.9999f  
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

解决方案
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. 

                        
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