In Hadoop HDFS (Hadoop Distributed File System), the hdfs dfs -chmod command is used to change the permissions of files and directories. It allows you to modify the access control settings (permissions) for HDFS files and directories, similar to the chmod command in a Unix-like file system.

The basic syntax for the hdfs dfs -chmod command is as follows:

• -R (optional): If you include the -R option, the command will recursively change permissions for all files and subdirectories under the specified path.

• <permissions>: This is the new set of permissions that you want to apply to the specified file or directory in HDFS. Permissions are represented as a three-character string, where each character represents the permission for the owner, group, and others, respectively. Each permission character can be one of the following:

  • r (read): Allows reading the file or directory.
  • w (write): Allows modifying (writing) the file or directory.
  • x (execute): Allows executing the file (for directories, it allows traversal).

• <path>: This is the HDFS path to the file or directory for which you want to change the permissions.

Examples:

1. To grant read and write permissions to the owner of a file named “example.txt” in HDFS, you can use the following command:

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   hdfs dfs -chmod u+rw example.txt

2. To remove execute permission for others (everyone else) from a directory named “my_directory” in HDFS, you can use:

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   hdfs dfs -chmod o-x my_directory

3. To grant read and execute permissions to both the owner and the group for a file named “data.csv” in HDFS, you can use:

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   hdfs dfs -chmod ug+rx data.csv

4. To set specific permissions using octal notation (e.g., 755 for owner: read, write, execute; group: read, execute; others: read, execute) on a file “script.sh,” you can use:

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   hdfs dfs -chmod 755 script.sh