TABLE 19.1 /etc/fstab Options
| Option | Purpose |
|---|---|
rw | Gives read and write access |
ro | Gives read-only access |
async | Writes data when the server, not the client, feels the need |
sync | Writes data as it is received |
The following is an example of an /etc/exports file:
# etc/exports file for myhost.mydomain.com
/usr/local yourhost(ro,show)
/home/ahudson *.yourdomain.com(rw,hide,sync)
This file /usr/local to yourhost. The mount is read-only (which is good for a directory of binary files that don't get written to). It also allows users on yourhost to see the contents of file systems that might be mounted on /usr/local. The second export mounts /home/ahudson to any host in yourdomain.com. It doesn't allow subsidiary file systems to be viewed, but you can read and write to the file system.
After you have finished with the /etc/exports file, you will check to see whether the NFS service is started by using the command:
# service nfs status
If you see a message saying that services are stopped, issue the following command:
# service nfs start
and watch as the related NFS services are started. When the services are started, you can enter the command
# /usr/sbin/exportfs -r
to export all the file systems in the /etc/exports file to a list named xtab under the /var/lib/nfs directory, which is used as a guide for mounting when a remote computer asks for a directory to be exported. The -r option to the command reads the entire /etc/exports file and mounts all the entries. The exportfs command can also be used to export specific files temporarily. Here's an example of using exportfs to export a file system:
# /usr/sbin/exportfs -o async yourhost:/usr/tmp
This command exports /usr/tmp to yourhost with the async option.
Be sure to restart the NFS server after making any changes to /etc/exports. If you prefer, you can use Fedora's system-config-nfs graphical client to set up NFS while using X. Start the client by going to System, Administration, Server Settings, NFS.
After you press Enter, you are prompted for the root password. Type in the password and click OK, and you see the main window. Click the Add button, and you see the Add NFS Share dialog box, as shown in Figure 19.1.
FIGURE 19.1 Fedora's system-config-nfs client can be used to quickly set up local directories for export via NFS.
In the Directory text box, type a name of a directory to be exported; in the Host(s) text box, type a hostname or the IP address of a remote host that is to be allowed access to the directory. By default, a directory is exported as read-only, but you can choose read and write access by clicking either option in the Basic Permissions area of the dialog box. When finished, click the OK button, click the Apply button, and then use the File menu to quit.
As part of your configuration for using NFS, you might need to enable the port on your firewall. Go to System, Administration, Firewall to open the Firewall configuration utility. Check the box next to NFS4 and click Apply to apply the new firewall policy.
NFS Client Configuration
To configure your host as an NFS client (to acquire remote files or directories), edit the /etc/fstab file as you would to mount any local file system. However, rather than use a device name to be mounted (such as /dev/sda1), enter the remote hostname and the desired file system to be imported. For example, one entry might look like this:
# Device Mount Point Type Options Freq Pass
yourhost:/usr/local /usr/local nfs nfsvers=4,ro 0 0
If you use autofs on your system, you need to use proper autofs entries for your remote NFS mounts. See the section 5 man page for autofs.
The options column uses the same options as standard fstab file entries with some additional entries, such as nfsvers=4, which specifies the fourth version of NFS. You can also use the mount command, as root, to quickly attach a remote directory to a local file system by using a remote host's name and exported directory. For example:
# mount -t nfs 192.168.0.11:/home/andrew
/home/andrew/test/foo
After you press Enter, the entire remote directory appears on your file system. You can verify the imported file system by using the df command, like so:
# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
73575592 58627032 11150752 85% /
/dev/sda1 101086 18697 77170 20% /boot
