Explain Common Hadoop Shell Commands
1. Create a directory in HDFS at given path(s).
Usage:
hadoop fs -mkdir <paths> Example:
hadoop fs -mkdir /user/saurzcode/dir1 /user/saurzcode/dir2
2. List the contents of a directory.
Usage :
hadoop fs -ls <args> Example:
hadoop fs -ls /user/saurzcode
3. Upload and download a file in HDFS.
hadoop fs -put: Copy single src file, or multiple src files from local file system to the Hadoop data file system
Usage:
hadoop fs -put <localsrc> ... <HDFS_dest_Path> Example:
hadoop fs -put /home/saurzcode/Samplefile.txt /user/saurzcode/dir3/
Download:
hadoop fs -get: Copies/Downloads files to the local file system
Usage:
hadoop fs -get <hdfs_src> <localdst> Example:
hadoop fs -get /user/saurzcode/dir3/Samplefile.txt /home/
4. See contents of a file
Same as unix cat command:
Usage:
hadoop fs -cat <path[filename]> Example:
hadoop fs -cat /user/saurzcode/dir1/abc.txt
5. Copy a file from source to destination
This command allows multiple sources as well in which case the destination must be a directory.
Usage:
hadoop fs -cp <source> <dest> Example:
hadoop fs -cp /user/saurzcode/dir1/abc.txt /user/saurzcode/dir2
6. Copy a file from/To Local file system to HDFS
copyFromLocal
Usage:
hadoop fs -copyFromLocal <localsrc> URI Example:
hadoop fs -copyFromLocal /home/saurzcode/abc.txt /user/saurzcode/abc.txt
Similar to put command, except that the source is restricted to a local file reference. copyToLocal
Usage:
hadoop fs -copyToLocal [-ignorecrc] [-crc] URI <localdst>
Similar to get command, except that the destination is restricted to a local file reference.
7. Move file from source to destination.
Note: - Moving files across file system is not permitted.
Usage :
hadoop fs -mv <src> <dest> Example:
hadoop fs -mv /user/saurzcode/dir1/abc.txt /user/saurzcode/dir2
8. Remove a file or directory in HDFS.
Remove files specified as argument. Deletes directory only when it is empty
Usage :
hadoop fs -rm <arg> Example:
hadoop fs -rm /user/saurzcode/dir1/abc.txt
Recursive version of delete.
Usage :
hadoop fs -rmr <arg>
Example:
hadoop fs -rmr /user/saurzcode/
9. Display last few lines of a file.
Similar to tail command in Unix.
Usage :
hadoop fs -tail <path[filename]> Example:
hadoop fs -tail /user/saurzcode/dir1/abc.txt
10. Display the aggregate length of a file.
Usage :
hadoop fs -du <path> Example:
hadoop fs -du /user/saurzcode/dir1/abc.txt
