CD Actual 13/CDA13.ISO/DOC/HOWTO/OTHER_FO/SGML/MINI/NFS_ROOT.GZ/NFS-Root.sgml

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<article>

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<title>NFS-Root Mini-Howto
<author>Andreas Kostyrka, <tt/[e-mail]/
<date>V5, 14 March 1996
<abstract>
This Mini-HOWTO tries explains how to setup a ``disc-less'' Linux
workstation, which mounts it's root filesystems via NFS.
The newest version of this Mini-Howto can always be found in
<tt>ftp://ftp.ag.or.at/people/andreas/</tt>.
</abstract>

<toc>

<sect> Copyright
<p>
(c) 1996 Andreas Kostyrka ([e-mail] or [e-mail]) <p>
Unless otherwise stated, Linux HOWTO documents are copyrighted by their
respective authors. Linux HOWTO documents may be reproduced and distributed
in whole or in part, in any medium physical or electronic, as long as
this copyright notice is retained on all copies. Commercial redistribution
is allowed and encouraged; however, the author would like to be notified of
any such distributions.

All translations, derivative works, or aggregate works incorporating
any Linux HOWTO documents must be covered under this copyright notice.
That is, you may not produce a derivative work from a HOWTO and impose
additional restrictions on its distribution. Exceptions to these rules
may be granted under certain conditions; please contact the Linux HOWTO
coordinator at the address given below.

In short, we wish to promote dissemination of this information through as
many channels as possible. However, we do wish to retain copyright on the
HOWTO documents, and would like to be notified of any plans to redistribute
the HOWTOs.

If you have questions, please contact Andreas Kostyrka
<<tt/mailto:[e-mail]/>, the author of this mini-HOWTO, or
Greg Hankins, the Linux HOWTO coordinator, at
<<tt/mailto:[e-mail]/> via email, or at +1 404 853
9989.

<sect1>Contributors
<p>
<itemize>
<item>
Avery Pennarun <<tt/[e-mail]/> (how to boot without <bf/LILO/)
</itemize>

<sect>General Overview
<p>
Generally speaking there are the following problems for the
workstation:
<itemize>
<item>It must find out it's own IP-address, and if needed also the
rest of the Ethernet configuration.
<item>
It must know the <em/NFS/-server and the mount path to it's root
filesystem.
</itemize>
<p>
The current implementation of <em/NFSROOT/ in the Linux kernel (as of
1.3.7x) allows for
the following ``solutions'':
<itemize>
<item>The IP-address may be discovered by <em/RARP/, or the full
ethernet configuration may be passed to the kernel via kernel
parameters by <bf/LILO/ or <bf/LOADLIN/.
<item>The <em/NFS/-path to mount can be passed via kernel
parameters. If this is not done, the kernel assumes the
<em/RARP/-server also as <em/NFS/-server, and uses compiled in default
for the path part. (current default value in the kernel:
<tt>/tftpboot/<<em/IP-address of the machine/></tt>.)
</itemize>

Before starting to setup a discless enviroment, you should decide if
you will be booting via <bf/LILO/ or <bf/LOADLIN/. The advantage of
doing so is flexibility, the disadvantage is speed. Booting a Linux
kernel without <bf/LILO/ is faster. This may or may not be a
consideration.

<sect>
Setup on the server
<sect1>Compiling the kernels
<p>
<em/RARP/ support in the kernel of the server will probably be a good
idea. You must have it if you will boot without kernel parameters. On
the other hand it doesn't help you, if the client isn't on the same
subnet than the server.
<p>
The kernel for the workstation needs the following as a minimum set
compiled in:
<itemize>
<item> <em/NFS/-filesystem compiled in. (It doesn't need to have
<em/ext2/-support compiled in, a module suffices.)
<item> ``Root on NFS'' must be enabled.
<item> The Ethernet driver for the network card of the workstation
must be compiled in.
</itemize>
<p>
If the workstation will be booted without kernel parameters, you need
also to set the root device to 0:255. Do this by creating a dummy
device file with <tt>mknod /dev/nfsroot b 0 255</tt>. After having
created such a device file, you can set root device of the kernel
image with <tt>rdev <<em/kernel-image/> /dev/nfsroot</tt>.
<sect1>
Creation of the root filesystem
<sect2>
Copying the filesystem
<p>
After having decided where to place the root tree, create it with
(e.g.) <tt>mkdir -p <<em/directory/></tt> and
<tt>tar cClf / - | tar xpCf <<em/directory/> -</tt>.
<p>
If you boot your kernel without LILO, then the rootdir has to be
<tt>/tftpboot/<<em/IP-address/></tt>. If you don't like it, you
can change it in the top Makefile in the kernel sources, look for a line like:
<tt>NFS_ROOT = -DNFS_ROOT="\"/tftpboot/%s\""</tt>
      If you change this, you have to recompile the kernel.
<p>
<sect2>
Changes to the root filesystem
<p>
Now trim the unneeded files, and check the /etc/rc.d scripts. Some
important points:
<itemize>

<item> One important thing is eth0 setup. The workstation comes up
with a, at least partially, setup eth0. Setting up the
IP-address of the workstation to the the IP-Address of the server
is not considered a clever thing to do. (As it happened to the author
on one of his early attempts.)

<item>
Another point is the /etc/fstab of the workstation. It should
be setup for nfs filesystems.

<item> <bf/WARNING/: Don't confuse the server root filesystem and the
        workstation root filesystem. (I've already patched up a
        rc.inet1 on the server, and wondered why the workstation still
        didn't work.)
</itemize>

<sect2>
Exporting the filesystem
<p>
Export the root dir to the work station. See <tt/exports(5)/. You
most likely will have to restart the nfsd/mountd after this change.

<sect2>
RARP setup
<p>
Setup the <em/RARP/ somewhere on the net. If you boot without a
      nfsroot parameter, the <em/RARP/ server has to be the <em/NFS/
      server. Usually this will be the <em/NFS/ server. To do this, you
      will need to run a kernel with <em/RARP/ support.
<p>
      To do this, execute (and install it somewhere in <tt>/etc/rc.d</tt> of
      the server!):
<p>
<tt>/sbin/rarp -s <<em/ip-addr/> <<em/hardware-addr/></tt>
<p> where
<descrip>
<tag/ip-addr/ is the IP address of the workstation, and
<tag/hardware-addr/  is the Ethernet address of the network card of
                       the workstation.
</descrip>
<p>
      example: <tt>/sbin/rarp -s 131.131.90.200 00:00:c0:47:10:12</tt>
<p>
      You can also use a symbolic name instead of the IP-address, as
      long the server is able to find out the IP-address. (/etc/hosts
      or <em/DNS/ lookups)

<sect2>
Finding out hardware addresses
<p>
I don't know the hardware address! How can I find it out?
<itemize>
<item> Boot the kernel disk you made, and watch for the line where
          the network card is recognized. It usually contains 6 hex
          bytes, that should be the address of the card.
<item> Boot the workstation with some OS with TCP/IP networking
          enabled. Then ping the workstation from the server. Look in
          the ARP-cache by executing:
          <tt>/sbin/arp -a</tt>
</itemize>

<sect>
Booting the workstation
<p>
<sect1>
Using a raw kernel disc
<p>
If you have exported the root filesystem with the correct name for the
default naming and your <em/NFS/ server is also the <em/RARP/ server
(which implies that the boxes are on the same subnet.), than you can
just boot the kernel by <tt/cat/ing it to a disc. (You have to set the
root device in the kernel to 0:255.)
<sect1>
Using a bootloader & <em/RARP/
<p>
     Give the kernel all needed parameters when booting, and add
     <tt>nfsroot=<<em/server-ip-addr/>:<<em>/path/to/mount</em>></tt>
     where <em/server-ip-addr/ is the IP-address of your NFS-server, and
     <em>/path/to/mount</em> is the path to the root directory.

Tips:
<itemize>
<item> When using <bf/LILO/ consider using the ``<tt/lock/'' feature: Simply
            type in once all the correct parameters and add
            ``<tt/lock/''. Next time when booting let LILO timeout.
<item> When generating a workstation specific boot disk, you can
            also use the <tt/append=/ feature in <tt/lilo.conf/.
</itemize>
<sect1>
Using a bootloader without <em/RARP/
<p>
     In addition to <tt/nfsroot/ give a
<tt>nfsaddrs=<<em/wst-IP/>:<<em/srv-IP/>:<<em/gw-IP/>:<<em/netm-IP/>:<<em/hostname/></tt>
     commandline argument for the kernel. The kernel will setup <tt/eth0/
     with the given parameters:
<descrip>
<tag/wst-IP/    machine's IP-Address
<tag/srv-IP/    NFS-server IP-Address
<tag/gw-IP/     gateway
<tag/netm-IP/   netmask
<tag/hostname/  machine name
</descrip>
<sect>
Other topics
<p>
<itemize>
<item> There is BOOTP client:
<tt>ftp://sunsite.unc.edu/system/Network/admin/bootpc.v045.tgz</tt>
<p>
With the new bzImage+initrd patches (which to my knowledge made it
into 1.3.73), it could be made to work for diskless stations quite
nicely.
</itemize>
</article>