33 Frequently Used HDFS Shell Commands

# Open a terminal window to the current working directory. # /home/training

# 1. Print the Hadoop version hadoop version

# 2. List the contents of the root directory in HDFS # hadoop fs -ls /

# 3. Report the amount of space used and # available on currently mounted filesystem # hadoop fs -df hdfs:/

# 4. Count the number of directories,files and bytes under # the paths that match the specified file pattern # hadoop fs -count hdfs:/

# 5. Run a DFS filesystem checking utility # hadoop fsck – /

# 6. Run a cluster balancing utility # hadoop balancer

# 7. Create a new directory named “hadoop” below the # /user/training directory in HDFS. Since you’re # currently logged in with the “training” user ID, # /user/training is your home directory in HDFS. # hadoop fs -mkdir /user/training/hadoop

# 8. Add a sample text file from the local directory # named “data” to the new directory you created in HDFS # during the previous step. # hadoop fs -put data/sample.txt /user/training/hadoop

# 9. List the contents of this new directory in HDFS. # hadoop fs -ls /user/training/hadoop

# 10. Add the entire local directory called “retail” to the # /user/training directory in HDFS. # hadoop fs -put data/retail /user/training/hadoop

# 11. Since /user/training is your home directory in HDFS, # any command that does not have an absolute path is # interpreted as relative to that directory. The next # command will therefore list your home directory, and # should show the items you’ve just added there. # hadoop fs -ls

# 12. See how much space this directory occupies in HDFS. # hadoop fs -du -s -h hadoop/retail

# 13. Delete a file ‘customers’ from the “retail” directory. # hadoop fs -rm hadoop/retail/customers

# 14. Ensure this file is no longer in HDFS. # hadoop fs -ls hadoop/retail/customers

# 15. Delete all files from the “retail” directory using a wildcard. # hadoop fs -rm hadoop/retail/*

# 16. To empty the trash # hadoop fs -expunge

# 17. Finally, remove the entire retail directory and all # of its contents in HDFS. # hadoop fs -rm -r hadoop/retail

# 18. List the hadoop directory again # hadoop fs -ls hadoop

# 19. Add the purchases.txt file from the local directory # named “/home/training/” to the hadoop directory you created in HDFS # hadoop fs -copyFromLocal /home/training/purchases.txt hadoop/

# 20. To view the contents of your text file purchases.txt # which is present in your hadoop directory. # hadoop fs -cat hadoop/purchases.txt

# 21. Add the purchases.txt file from “hadoop” directory which is present in HDFS directory # to the directory “data” which is present in your local directory # hadoop fs -copyToLocal hadoop/purchases.txt /home/training/data

# 22. cp is used to copy files between directories present in HDFS # hadoop fs -cp /user/training/*.txt /user/training/hadoop

# 23. ‘-get’ command can be used alternaively to ‘-copyToLocal’ command # hadoop fs -get hadoop/sample.txt /home/training/

# 24. Display last kilobyte of the file “purchases.txt” to stdout. # hadoop fs -tail hadoop/purchases.txt

# 25. Default file permissions are 666 in HDFS # Use ‘-chmod’ command to change permissions of a file # hadoop fs -ls hadoop/purchases.txt sudo -u hdfs hadoop fs -chmod 600 hadoop/purchases.txt

# 26. Default names of owner and group are training,training # Use ‘-chown’ to change owner name and group name simultaneously # hadoop fs -ls hadoop/purchases.txt sudo -u hdfs hadoop fs -chown root:root hadoop/purchases.txt

# 27. Default name of group is training # Use ‘-chgrp’ command to change group name # hadoop fs -ls hadoop/purchases.txt sudo -u hdfs hadoop fs -chgrp training hadoop/purchases.txt

# 28. Move a directory from one location to other # hadoop fs -mv hadoop apache_hadoop

# 29. Default replication factor to a file is 3. # Use ‘-setrep’ command to change replication factor of a file # hadoop fs -setrep -w 2 apache_hadoop/sample.txt

# 30. Copy a directory from one node in the cluster to another # Use ‘-distcp’ command to copy, # -overwrite option to overwrite in an existing files # -update command to synchronize both directories # hadoop fs -distcp hdfs://namenodeA/apache_hadoop hdfs://namenodeB/hadoop

# 31. Command to make the name node leave safe mode # hadoop fs -expunge sudo -u hdfs hdfs dfsadmin -safemode leave

# 32. List all the hadoop file system shell commands # hadoop fs

# 33. Last but not least, always ask for help! # hadoop fs -help

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