Sunday, August 2, 2015

Hadoop Command Line


All Hadoop commands are invoked by the bin/hadoop script. Running the hadoop script without any arguments prints the description for all commands.

hadoop [--config confdir] [COMMAND] [GENERIC_OPTIONS] [COMMAND_OPTIONS]

The File System (FS) shell includes various shell-like commands that directly interact with the Hadoop Distributed File System (HDFS) as well as other file systems that Hadoop supports, such as Local FS, HFTP FS, S3 FS, and others. The FS shell is invoked by:
bin/hadoop fs

Hadoop comes with a number of command-line tools that enable basic filesystem operations. HDFS commands are subcommands of the hadoop command-line utility. To display basic usage information, the command is:

hadoop fs  

Hadoop uses fs.default.name value in core-site.xml file if full url syntax is not used.  Command to list files in a dir.

hadoop fs -ls /user/myid
or
hadoop fs -ls hdfs://NameNode.blah.com:8020/home/myid

Command to upload file with -put or -copyFromLocal which copies file form local filesystem

hadoop fs -put /etc/mytest.conf /user/myid/

To download file from HDFS using -get or -copyToLocal.

hadoop fs -get /user/myid/mytest.conf ./

Process to set a replication factor for a file or dir of files with the -R

hadoop fs -setrep 5 -R /user/myid/rep5/

fsck is command to run HDFS filesystem checking utility. Run a fsck on the files we set the rep factor on and see if it looks correct

hadoop fsck /user/myid/rep5 -files -blocks -locations

These are basic frequently used HDFS commands using command line operations.

1 comment:

  1. We always follow configurations, tweaks, installations and other important stuff from this website related to hadoop because we were referred to this site by our hadoop online training center instructors. Thanks.

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