MS-DOS 6.22 Network Share File Permissions

MS-DOS 6.22 does not natively possess a multi-user security model or network-level access control, relying entirely on external network redirectors and remote host servers to enforce file permissions. This article explains the architectural mechanics of how MS-DOS 6.22 interacts with local area networks, how external client software bridges the operating system to remote shares, and how server-side access rights are translated into standard DOS errors.

The Role of the FAT File System and Local Limitations

Locally, MS-DOS 6.22 operates on the FAT16 file system, which contains no provisions for Access Control Lists (ACLs), user ownership, or multi-user privilege levels. The only file-level flags available are traditional DOS attributes: Read-Only, Hidden, System, and Archive. Because the operating system runs completely in real mode with single-user execution, it lacks a kernel-level security subsystem to restrict access to local storage.

The Redirector Architecture

To access network shares, MS-DOS 6.22 relies on an external network client, such as Microsoft Network Client 3.0 for MS-DOS, LAN Manager, or Novell NetWare’s NETX/VLM shell.

When a network client is loaded, it hooks into the MS-DOS interrupt architecture—specifically INT 21h (DOS API) and INT 2Fh (the Multiplex Interrupt, function 11h for network redirection). When an application requests an operation on a network-mapped drive letter (such as X: mapped via NET USE), MS-DOS routes the file input/output request to the redirector TSR (Terminate and Stay Resident) driver instead of the local disk driver.

Server-Side Permission Enforcement

All access control is enforced remotely by the server hosting the share (such as Windows NT, OS/2 LAN Server, Novell NetWare, or Linux running Samba).

  1. Authentication: During connection establishment, the MS-DOS network client transmits credentials (username and password) to the server.
  2. Evaluation: The server validates the credentials and assigns session permissions based on its native security system (such as NTFS ACLs or NetWare Trustee Rights).
  3. Execution: When MS-DOS attempts to open, read, write, or delete a file, the request is packaged into a network protocol (such as SMB or NCP) and sent to the host. The server decides whether to permit or reject the request.

MS-DOS 6.22 remains completely unaware of the underlying permission structures on the host. It simply requests the file action and waits for the server's response.

Translation of Network Errors

If a user attempts an unauthorized operation—such as writing to a read-only share, creating a file without directory write privileges, or executing a restricted file—the server denies the network packet.

The local network redirector receives this rejection and translates the server-specific error into a standard DOS error code. Most network permission violations are translated directly to DOS Error Code 05h (Access Denied). The running DOS application or the command shell (COMMAND.COM) then surfaces this error to the user via standard system messages, such as "Access denied" or the traditional critical error prompt ("Abort, Retry, Fail?").