To enable a user to "read and navigate to" a directory, two specific permissions are required: read (r) and execute (x). The read permission allows the user to list the contents of the directory. The execute permission, often called the "search" or "traverse" permission for directories, allows the user to enter the directory (e.g., using the cd command). The command setfacl --modify user:user2:r-x mydirectory uses an Access Control List (ACL) to grant both of these necessary permissions to the specific user (user2) without altering the base permissions for the owner, group, or others.

A. The --default flag sets ACLs for new items created inside the directory, not for the directory itself, and it omits the required execute (x) permission.

B. This command grants only read (r) permission, which is insufficient for navigating into the directory.

C. The -x option is for removing an ACL entry, which is the opposite of the required action.

E. This command modifies permissions for the group test, not the specific user user2, and it fails to grant the necessary execute (x) permission.

1. Oracle® Linux 8 Documentation

Managing File Systems

Chapter 10. Managing File System ACLs

Section 10.3. Setting ACLs. This document details the usage of the setfacl command with the -m or --modify option to set permissions for a specific user or group on a file or directory. It provides examples such as setfacl -m u:username:r-x file

which directly corresponds to the correct answer's syntax.

2. Red Hat Enterprise Linux 8 Documentation

Configuring basic system settings

Chapter 10. Using access control lists

Section 10.2. File system permissions. This official source clarifies the meaning of directory permissions: "For directories

the r (read) permission allows to list the directory's contents

and the x (execute) permission allows to enter the directory." This directly supports the requirement for r-x to fulfill the question's prompt.

3. University of Illinois

CS 241: System Programming Courseware

Guide to Unix Permissions. This academic resource explains the distinction for directory permissions: "Execute: For a directory

this permission (also called 'search') allows you to enter the directory (i.e. cd into it) and access any of its files." This confirms that the "navigate" requirement translates to the execute (x) permission.