CompTIA Linux+ XK0-006 (V8) Practice Question

The correct command is chmod 751 backup.sh. In Linux, file permissions can be set using a three-digit octal number where each digit represents a permission set for the user (owner), group, and others, respectively.

The required permissions are calculated as follows:

• User (Owner): Read (4) + Write (2) + Execute (1) = 7
• Group: Read (4) + Execute (1) = 5
• Others: Execute (1) = 1

Combining these values results in the octal code 751.

• chmod 755 backup.sh is incorrect because it would grant read and execute permissions to 'others', violating the policy that they should only have execute permission.
• chmod 651 backup.sh is incorrect because it would deny the execute permission for the owner (read + write = 6), preventing the owner from running the script.
• chmod 740 backup.sh is incorrect because it would only grant read permission to the group (denying the required execute permission) and no permissions at all to 'others'.