Configuring and Using NFS
Pages: 1, 2
Now, login as root at alpha.
And select "Configure," then "Networking"; use your spacebar to select the NFS client and press OK, then exit out of
Before we try mounting gamma's
/usr directory at alpha, let's create a mountpoint on alpha:
Now issue the mount command:
mount gamma:/usr /share
If you issued this as root, you should receive your command prompt back without any error messages. To see if it mounted:
which should return a line that reads something like this:
gamma:/usr 5996471 1069259 4447495 19% /share
and if you issue these commands:
cd /share ls
you should be able to see the contents of gamma's
When you are finished, you can unmount
/share like any other mounted file system:
Congratulations, you've just created your first NFS server; now let's fine-tune it a bit.
Normally, you won't want to export your entire
structure. Even if permissions are set correctly, you don't want remote
users poking about your home and bin directories. Instead, create a
/usr to contain the information you want remote users to
access. As a practical example, I copy the packages collection into a
directory I've created called
/usr/packages. I then export
/usr/ports, so my
/etc/exports looks like this:
/usr/ports 10.0.0.1 /usr/packages 10.0.0.1
The new mount command at alpha is:
mount gamma:/usr/packages /share cd /share ls
The above command will only show the packages collection stored on
gamma. An added side benefit to the client is that they don't have to copy
a package onto their hard drive in order to install it. The
command works quite nicely from the mountpoint.
NFS's behaviour is a little weird if you want to share your CD-ROM over
the network. If I edit
/etc/exports on gamma to add the following line:
/cdrom -alldirs 10.0.0.1
I would expect alpha to be able to access the contents of a data CD-ROM located on gamma. If I put a data CD-ROM in gamma's CD-ROM drive, and at alpha type:
mount gamma:/cdrom /share
nfs: can't access /cdrom: Permission denied
Hmmmm... Let's try a
shutdown now at gamma; perhaps nfsd needs to re-read
/etc/exports. No, that made things worse, as the boot messages now include:
Starting final network daemons: mountdJun 3 15:25:48 gamma mountd: could not remount /cdrom: Invalid argument Jun 3 15:25:48 gamma mountd: bad exports list line /cdrom -alldirs 10.0.0.1
If I wait long enough, I'll also start to get periodic error messages at
Alt-F1. So what happened? Let's take a look at
# Device Mountpoint FStype Options Dump Pass# /dev/acd0c /cdrom cd9660 ro,noauto 0 0
And there's one problem: I tried to export a filesystem that is not set
to mount automatically when I reboot. I can't export a filesystem that
isn't mounted locally. To complicate matters further, I can't export a
directory I've created, unless I create it as a subdirectory of
/usr. This is where NFS gets a bit weird. Try this at gamma:
mkdir /usr/cdrom pico /etc/exports
and modify the line to read:
/usr/cdrom -alldirs 10.0.0.1
Save the change and issue a
shutdown now. This time there shouldn't be any error messages. Now try
and you'll see something like this:
Filesystem 1K-blocks Used Avail Capacity Mounted on /dev/ad0s1a 49583 33637 11980 74% / /dev/ad0s1f 5996471 1069263 4447491 19% /usr /dev/acd0c 470754 470754 0 100% /usr/cdrom /dev/ad0s1e 19815 5671 12559 31% /var procfs 4 4 0 100% /proc mfs:1919 68647 1 63155 0% /tmp
/usr/cdrom was mounted for you; if you try
you'll see something like
cd9660: Device busy
cd /usr/cdrom ls
should show the contents of the CD-ROM. Now, at alpha,
mount gamma:/usr/cdrom /share cd /share ls
should also show the contents of gamma's CD-ROM.
cd / umount /share
You will have to be extra careful if you decide to export CD-ROMs; you
don't want to inadvertently eject a mounted CD-ROM or reboot without a
CD-ROM in your CD-ROM drive. I usually leave the cdrom reference commented
/etc/exports like so:
#/usr/cdrom -alldirs 10.0.0.1
and uncomment it out when I actually want to share my CD-ROM. I then need
to issue a
shutdown now so the
nfsd can mount the CD-ROM. If I try to mount it myself:
mount: /usr/cdrom: unknown special file or file system
nfsd has mounted it, I can unmount it normally:
This should get you started with NFS; read the man page for nfsd to learn how to give read-only access, group access, and user access.
Whenever you edit
/etc/exports, always test your changes at the
client. Mount the newly exported data to ensure that you haven't given the
client access to more data then you intended.
One final note on NFS: portmap can be a security risk on computers
attached to insecure networks such as the Internet. Usually, in a
networked environment, there is only one computer with the Internet
connection as it controls Internet access for the rest of the
network. Don't run the
nfsd on that computer.
Next week, we'll start familiarizing ourselves with the shells that come with your FreeBSD system.
Dru Lavigne is a network and systems administrator, IT instructor, author and international speaker. She has over a decade of experience administering and teaching Netware, Microsoft, Cisco, Checkpoint, SCO, Solaris, Linux, and BSD systems. A prolific author, she pens the popular FreeBSD Basics column for O'Reilly and is author of BSD Hacks and The Best of FreeBSD Basics.
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