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macOS as NFS Server

Sharing Data via NFS

macOS can share folders of its own file system for access in the network via the NFS protocol.

NOTE: NFS and UNIX systems often use the word export to refer to an NFS share. This manual and NFS Manager are using the term share only.

Due to the architecture of NFS to be designed as a distributed file system, it is common

The access privileges for users and groups are controlled by the permission settings of each single file and folder, not by settings for the share. A share can only define access restrictions for computers.

Creating or changing NFS shares

To work with NFS shares, select the item NFS Server > Share Definitions in the left overview column of the control window, or select the menu item Configuration > Show Share Definitions. The list of shared folders will be displayed in a table at the right side of the window. After selecting a line in the table, detail information about this share will be shown below the table. This data can be modified as desired.

Perform the following steps to adjust the settings of a share to your needs:

  1. Press the button Select… next the to the line Folder to share to choose a local folder which should be made available to the network. Please also see the notes below in the section “Limitations of NFS shares”.
  2. Use the other controls to define the settings for this share.

If all write operations to this share should be blocked even if the respective user would have write permission, leave the checkmark at the field Share “read only” set. Otherwise you’ll have to remove the checkmark.

After a certain folder has been selected for sharing, its absolute path will become the share name other computers must use for mounting. Other computers will see the whole file hierarchy within (or “below”) that folder. If computers should additionally be allowed to mount a subfolder of the shared folder, check the option Allow clients to also mount objects in the shared folder. Example: Instead of /share other systems may also mount /share/subfolder if desired.

Mapping user and group accounts between client and server

The pop-up button User Mapping defines how users and groups of accessing computers should be mapped to users and groups of the sharing computer. The security model of NFS allows certain limitations:

Security settings when using Kerberos

If your network defines a Kerberos realm and a respective Kerberos Key Distribution Center is available, NFS shares can be protected by additional security features and data transfer can be encrypted. The pop-up button Minimum Security specifies what security features an accessing computer (and Kerberos user) have to support at least to be granted access to this share.

Limit access to certain computers

Because NFS is designed as distributed file system and no authentication is needed, access to shared folders should be limited to well-defined “trusted” clients. The basic settings are defined by the pop-up button Access permission:

Further options

Additional settings for the NFS share can be specified in a dialog window which will open after the button Show advanced options has been pressed. These options are described in detail on a separate page.

Special restrictions to consider when sharing files for video or audio media boxes

You may like to use the NFS server to share media files with your network, e.g. movies or music. The media can then be accessed by player devices (“media boxes”) connected to your TV or home-stereo equipment, under the condition the player supports the NFS protocol standard. Those players often underly certain limitations, because they don’t contain a fully featured operating system. For more information about typical problems experienced with media boxes in practice, please see this solutions page.

Repairing a damaged share configuration

If you have tried to configure the NFS server manually, without the help of NFS Manager, or if you have used a third-party application which is not perfectly adapted to your current version of macOS, the share configuration might have been damaged in a way that the NFS server shuts down completely. NFS Manager is capable of detecting this problem, giving you a chance to remove the broken configuration file, beginning with a new, empty one. In this case, all user interface elements of the item Share Definitions will be blocked and the message The current share configuration is invalid. will appear in red below the share table. Press the button More info… to open a special repair panel and display further details about the problem. You can either

In case the problem details indicate that a shared folder has been removed or renamed, you can of course fix this problem by other means (e.g. recreating the missing folder with the Finder), then let NFS Manager re-read the configuration.

When erasing the current configuration, the invalid definition entries are saved to a backup file. You will find it at /etc/exports-INVALID.backup. Experienced system administrators can use this file to recover some of the previous share entries.

Limitations of NFS shares

When creating NFS shares, four basic rules must always be respected:

  1. In principle, any physical file system (in Macintosh terminology each disk volume of a hard drive) or one of its subfolders can be shared.
  2. Sharing a subfolder of a folder which is shared already is permitted only if this subfolder is located on a different physical file system. (This is the case if the shared folder contains the mount point of another volume.)
  3. Sharing a super-folder of a folder which is shared already is permitted only if this super-folder is located on a different physical file system.
  4. Only local file systems can be shared. (It is not permitted to share a file system mounted via network from another computer.)

Those four basic rules are based on the architecture of the NFS design. They always have to be fulfilled, no matter which operating system is used. In addition, the following rules apply when using macOS:

IMPORTANT: If one of these rules has been violated, macOS will reject the affected or even all shares. In that case, the NFS server won’t work as expected. NFS Manager tries to find violations of the rules in advance. When contradictory share definitions are found, error messages will be shown.