How AFS Interprets the UNIX Mode Bits
| Chapter 14. Managing Access Control Lists |

## How AFS Interprets the UNIX Mode Bits

Although AFS uses ACLs to protect file data rather than the mode bits that UFS uses, it does not ignore the mode bits entirely. When you issue the chmod command on an AFS file or directory, AFS changes the bits appropriately. To change a file's mode bits, you must have the AFS w (write) permission on the ACL of the file's directory. To change a directory's mode bits, you must have the d (delete), i (insert), and l (lookup) permissions on its ACL.

AFS also uses the UNIX mode bits as follows:

- It uses the initial bit to determine the element's type. This is the bit that appears first in the output from the ls -l command and shows the hyphen (-) for a file or the letter d for a directory.

- It does not use any of the mode bits on a directory.

- For a file, the first (owner) set of bits interacts with the ACL entries that apply to the file in the following way:

  - If the first r mode bit is not set, no one (including the owner) can read the file, no matter what permissions they have on the ACL. If the bit is set, users also need the r (read) and l permissions on the ACL of the file's directory to read the file.

  - If the first w mode bit is not set, no one (including the owner) can modify the file. If the w bit is set, users also need the w and l permissions on the ACL of the file's directory to modify the file.

  - There is no ACL permission directly corresponding to the x mode bit, but to execute a file stored in AFS, the user must also have the r and l permissions on the ACL of the file's directory.

Removing Obsolete AFS IDs from ACLs |  | Chapter 15. Managing Administrative Privilege