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Project: Linux Articles

Quick and dirty guide to diskless workstations

By Amit Chattopadhyay
Posted: ( 2000-09-27 13:33:30 EDT by FreeOS )

Diskless workstations can give a new lease of life to old machines that
are lying in your attic. A computer which  has only a network card, 8MB RAM,
low-end cpu and a very simple mother-board with no modem/cdrom/floppy is an
ideal candidate for the diskless transition.

Diskless workstations can give a new lease of life to old machines that are 
lying in your attic. Diskless nodes eliminate the cost of software upgrades, 
system administration costs, hard disk, cdrom etc. A computer which has
only a network card, 8MB RAM, low-end cpu and a very simple mother-board with 
no modem/cdrom/floppy is an ideal candidate for the diskless transition! 

The following guide will try to help you setup a diskless node as quickly and 
easily. The "server" in this article is the node which contains the files 
for the diskless node. In my example the server is Cel300, 64mb RAM running 
Red Hat 6.1, Kernel 2.2.12. The "diskless node" is the node which will be
able to run remote applications after booting into Linux from a bootrom. For 
example, my P100, 48mb RAM will be designated as the "diskless node".

The objective is to give the "diskless node" an IP address of 192.168.0.100 
once it boots up and then be able to run remote applications from the diskless 
node. So, let us get started.

There are 4 important steps that have to be completed:

. ETHERBOOT Setup
. TAGGED Kernel Image
. DHCP Setup
. Root FS Setup


ETHERBOOT Setup
---------------

Etherboot is a package for creating ROM images that can download code over
the network to be executed on an x86 computer. Etherboot requires the PC
architecture, it does not work for other Linux platforms such as Alphas or
Suns.

Step #1:
 
Download the latest version of etherboot from http://etherboot.sourceforge.net.
Make sure to install the rpm or untar it into a directory where you can locate 
all the files.

Inside the etherboot directory, locate the file NIC under the src directory. 
This file lists all the supported network cards and the name of the ROM 
that has to be built. For example to build a NE2000 PCI compatible ROM, I
would need to make nepci.rom. Other common hardwares are the NE1000/2000 ISA 
ROM (ne.rom) and the Realtek 8029 (rtl8029.rom)


The ROM can be loaded either from the memory of the network card or from a 
floppy. It is advisable to use a floppy to test the configuration before you 
ask someone to write the ROM onto your network card's EEPROM. 

Step #2:

To make a floppy ROM, insert a blank floppy into your first FDD and execute 
the following inside the etherboot directory.

# make bin32/.fd0 
For example, to make a RTL8029 floppy ROM, make bin32/rtl8029.fd0

Alternatively, you can make the ROM image.
# make bin32/.rom
Following my previous example, to make a RTL8029 ROM, make bin32/rtl8029.rom

Step #3:

Boot the "diskless node" with the floppy ROM you made. It should detect your 
network card and stop after displaying, "looking for dhcp server". 

Note down the hardware address of network card (7 hexadecimal number delimited 
by colon). For example, my RTL8029 had the hardware address 00:80:AD:89:22:13

TAGGED Kernel Image
-------------------

The "diskless node" will require a linux kernel image to load. This can be 
easily created, but requires certain special options to be set. Finally
the resultant bzImage/zImage has to be made into a special tagged image.

Step #4:

Set the following options before you compile a new kernel on your "server".

1. Enable "IP:Kernel Level Autoconfiguration". Enable "BOOTP support" below it.
   [Networking Options]
2. Enable "Root filesystem on NFS". [Filesystems/NFS]
3. Make sure to compile the "diskless node's" network hardware into the kernel.
   Finally create the kernel by using either, make zImage or make bzImage.

Step #5:

Inside the etherboot directory is a mknbi directory. mknbi is the package used 
to create the tagged image. If /tftpboot/ is not present then create it.

# mkdir /tftpboot

Assuming mknbi is in your path and you are in the newly compiled kernel 
directory (/usr/src/linux/arch/i386/boot)

# mknbi --output=/tftpboot/vmlinuz.test zImage --target=linux
[Note: replace zImage with bzImage if you compiled into a bziped kernel]

DHCP Setup
----------

Step #6:

Ensure that /etc/inetd.conf contains a line for starting tftp. Typically this 
will look like, 
tftp    dgram   udp     wait    root    /usr/sbin/tcpd in.tftpd /tftpboot

DHCP is Dynamic Host Configuration Protocol. It is used to control vital 
networking parameters of hosts (running clients) with the help of a server. 
DHCP is backward compatible with BOOTP.

Step #7:

Open a fresh /etc/dhcpd.conf which we will configure. Add the following
entry.

subnet 192.168.0.0 netmask 255.255.255.0 {
          filename "/tftpboot/vmlinuz.test";
          option subnet-mask 255.255.255.0;

          host banshee {
                  hardware ethernet 00:80:AD:89:22:13;
                  fixed-address 192.168.0.100;
                  filename "/tftpboot/vmlinuz.test";
          }

}

[Note: change hardware ethernet  to match your network card. 
fixed-address represents the IP address assigned to the diskless node once
it boots up. filename is the location of the tagged kernel image.]

You may also need to create an empty dhcpd.leases file in the /var/state/dhcpd 
directory.

Step #8:

Edit /etc/hosts to add an entry for the diskless node, for example:
192.168.0.100 banshee

Step #9:

Start the dhcp daemon on the server. Make sure it reports no errors.

# dhcpd

Step #10:
Boot the "diskless node" with the floppy ROM. Check to see that it finds 
the DHCP server and loads the kernel using tftp.


Root FS Setup
-------------

Download lts_core from http://www.ltsp.org/download/index.html. The RPM/TGZ 
contains a root file system which can be readily used. Alternatively you may 
want to read NFS-Root-Client HOWTO for more detailed instructions on manually 
creating your own root FS for the diskless node.

Step #11:

Copy ltsroot.tgz into /tftpboot

# tar xzpvf ltsroot.tgz
# cp -a ltsroot 192.168.0.100
# cd 192.168.0.100
# mkdir sbin
# cp /bin/umount ./bin

You should replace 192.168.0.100 with the IP address of the diskless
node. We shall add a local application (seti@home) that we want to run
on the diskless node. After copying setiathome.tar.gz into the 
/tftpboot/192.168.0.100 directory,

# tar xzpvf setiathome.tar.gz

The above will create a seti@home directory containing the seti files.

Step #12:

Make a /etc/exports file containing the following entries,
/tftpboot/192.168.0.100 (rw,no_root_squash)
/usr (ro,no_root_squash)
/bin (ro,no_root_squash)
/sbin (ro,no_root_squash)
/lib (ro,no_root_squash)

Step #13:

Edit /tftpboot/192.168.0.100/etc/inittab,
change "id:5:initdefault:" to "id:3:initdefault:"

This will ensure that a bash prompt starts up.

Step #14:

Load nfs and export the shares,

# nfs start
# exportfs -ra

Step #15:

Reboot the diskless node. The system should startup and give you a bash prompt.
Run the seti@home software which is a local copy for the diskless node.

Step #16: 

If you are happy with the settings, you should tell linux to startup 
dhcpd and nfs on the server everytime your server boots. This can usually be
added into the /etc/rc.d/rc.local file (for redhat)

NOTE on sharing files with server
---------------------------------

If you would like to share the binaries or other library files with the server, 
add the following entry into the /tftpboot/192.168.0.100/etc/fstab  (while at 
the server). Note that the "server" in this example has IP address of
192.168.0.1. You should change it to reflect the IP address of your server.

192.168.0.1:/bin /bin nfs
192.168.0.1:/sbin /sbin nfs
192.168.0.1:/usr /usr nfs
192.168.0.1:/lib /lib nfs

Reboot the diskless node. At the bash prompt, type
# mount -av

The contents of the server will now be available on your diskless node.
You can add the "mount -av" into your rc.sysinit.

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