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14.3. Exporting NFS File Systems

Sharing or serving files from an NFS server is known as exporting the directories. The NFS Server Configuration Tool can be used to configure a system as an NFS server.

To use the NFS Server Configuration Tool, you must be running the X Window System, have root privileges, and have the system-config-nfs RPM package installed. To start the application, select the Main Menu Button (on the Panel) => System Settings => Server Settings => NFS, or type the command system-config-nfs.

Figure 14-1. NFS Server Configuration Tool

To add an NFS share, click the Add button. The dialog box shown in Figure 14-2 appears.

The Basic tab requires the following information:

Figure 14-2. Add Share

The General Options tab allows the following options to be configured:

The User Access tab allows the following options to be configured:

To edit an existing NFS share, select the share from the list, and click the Properties button. To delete an existing NFS share, select the share from the list, and click the Delete button.

After clicking OK to add, edit, or delete an NFS share from the list, the changes take place immediately — the server daemon is restarted and the old configuration file is saved as /etc/exports.bak. The new configuration is written to /etc/exports.

The NFS Server Configuration Tool reads and writes directly to the /etc/exports configuration file. Thus, the file can be modified manually after using the tool, and the tool can be used after modifying the file manually (provided the file was modified with correct syntax).

14.3.1. Command Line Configuration

If you prefer editing configuration files using a text editor or if you do not have the X Window System installed, you can modify the configuration file directly.

The /etc/exports file controls what directories the NFS server exports. Its format is as follows:

directory hostname(options)

The only option that needs to be specified is one of sync or async (sync is recommended). If sync is specified, the server does not reply to requests before the changes made by the request are written to the disk.

For example,

/misc/export     speedy.example.com(sync)

would allow users from speedy.example.com to mount /misc/export with the default read-only permissions, but,

/misc/export     speedy.example.com(rw,sync)

would allow users from speedy.example.com to mount /misc/export with read/write privileges.

Refer to Section 14.3.2 Hostname Formats for an explanation of possible hostname formats.

Refer to the Red Hat Enterprise Linux Reference Guide for a list of options that can be specified.

CautionCaution
 

Be careful with spaces in the /etc/exports file. If there are no spaces between the hostname and the options in parentheses, the options apply only to the hostname. If there is a space between the hostname and the options, the options apply to the rest of the world. For example, examine the following lines:

/misc/export speedy.example.com(rw,sync)
/misc/export speedy.example.com (rw,sync)

The first line grants users from speedy.example.com read-write access and denies all other users. The second line grants users from speedy.example.com read-only access (the default) and allows the rest of the world read-write access.

Each time you change /etc/exports, you must inform the NFS daemon of the change, or reload the configuration file with the following command:

/sbin/service nfs reload

14.3.2. Hostname Formats

The host(s) can be in the following forms:

14.3.3. Starting and Stopping the Server

On the server that is exporting NFS file systems, the nfs service must be running.

View the status of the NFS daemon with the following command:

/sbin/service nfs status

Start the NFS daemon with the following command:

/sbin/service nfs start

Stop the NFS daemon with the following command:

/sbin/service nfs stop

To start the nfs service at boot time, use the command:

/sbin/chkconfig --level 345 nfs on

You can also use chkconfig, ntsysv or the Services Configuration Tool to configure which services start at boot time. Refer to Chapter 12 Controlling Access to Services for details.