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This article mainly introduces what are the common mistakes in hadoop. It is very detailed and has a certain reference value. Friends who are interested must finish reading it.

Start hadoop under the root account (provided that the hadoop account is not a root account), and then switch to the hadoop account after termination, and Permission Denied will appear.

2013-08-06 09 ERROR org.apache.hadoop.hdfs.server.namenode.FSNamesystem: FSNamesystem initialization failed.

Java.io.FileNotFoundException: / opt/data/hadoop/hdfs/name/in_use.lock (Permission denied)

The cause of the exception:

Because root will change the file permissions, use chown-R hadoop:hadoop / opt/data/hadoop/hdfs/* to change the user permissions.

Since slave does not have root@master 's ssh without key to log in, it will not operate the slave machine. If there is any, you can do the corresponding operation on the slave machine.

# View permissions of current folder

[hadoop@master current] $ll-a / opt/data/hadoop/hdfs/name/

Solution:

# stop hadoop cluster

Stop-all.sh

# exit the hadoop account, return to the root account permission, and change the current folder permission to hadoop

[root@master Desktop] # chown hadoop:hadoop / opt/data/hadoop/hdfs/name/current/*

# View permissions of current folder

[root@master Desktop] # ll-a / opt/data/hadoop/hdfs/name/current/

Total dosage 24

Drwxr-xr-x. 2 hadoop hadoop 4096 April 18 10:45.

Drwxrwxr-x. 5 hadoop hadoop 4096 April 18 11:25..

-rw-r--r--. 1 hadoop hadoop 4 April 18 10:45 edits

-rw-r--r--. 1 hadoop hadoop 2226 April 18 10:45 fsimage

-rw-r--r--. 1 hadoop hadoop 8 April 18 10:45 fstime

-rw-r--r--. 1 hadoop hadoop 99 April 18 10:45 VERSION

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