nfs4_getfacl

nfs4_getfacl is a command-line utility used to display the Access Control Lists (ACLs) of files and directories on NFSv4-mounted filesystems. ACLs provide more granular permission control than traditional UNIX file permissions, allowing detailed specifications of who can access files or directories and what operations they are permitted to perform.

This tool is typically used in environments where NFSv4 is employed, and administrators need to view or verify the ACLs to ensure the correct permissions are applied.

Purpose

• Display NFSv4 ACLs: nfs4_getfacl shows the current ACLs of files and directories in an NFSv4-mounted environment. It allows administrators to check who has access and what actions they can perform (read, write, execute).

• Verify Permission Settings: Helps system administrators verify that access control is set correctly and matches the intended security policies.

Basic Syntax

nfs4_getfacl [OPTIONS] <FILE>

• <FILE>: The file or directory whose ACLs will be displayed.

Common Options

• -a: Show all ACL entries (including special entries like owner and group).

  nfs4_getfacl -a file.txt

• -n: Display the ACL in a numeric format, showing the underlying numeric values for the permissions and IDs.

  nfs4_getfacl -n file.txt

• -d: Display the default ACL entries for a directory.

  nfs4_getfacl -d directory

• --help: Show help information about the command.

Example Usage

1. Displaying ACL of a File

   nfs4_getfacl file.txt

   This command displays the current ACL of file.txt, showing who has access and their specific permissions.

2. Displaying ACL in Numeric Format

   nfs4_getfacl -n file.txt

   This command shows the ACL in numeric form, revealing the raw numeric representation of the user and group permissions.

3. Showing Default ACL of a Directory

   nfs4_getfacl -d /shared

   This command displays the default ACL for the /shared directory. Default ACLs are applied to new files or directories created within the directory.

4. Displaying All ACL Entries for a File

   nfs4_getfacl -a file.txt

   This command displays all ACL entries, including special entries such as owner, group, and others.

Best Practices

• Regular ACL Review: Periodically review ACLs to ensure that they align with your organization’s security policies. Over time, as user roles change, permissions may need to be updated.

• Test Permissions: After reviewing ACLs, test file and directory access from the perspective of different users and groups to ensure that the permissions are functioning as expected.

• Use nfs4_getfacl Before Modifying ACLs: Always check the existing ACL using nfs4_getfacl before making changes with nfs4_setfacl. This helps avoid unintended permission modifications.

Conclusion

nfs4_getfacl is a crucial tool for inspecting the current access control settings of files and directories in NFSv4 environments. By allowing administrators to view detailed ACLs, it helps ensure that permission configurations are correct, enhancing both security and operational control.