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Get users diskless with Linux thin client

Vincent Danen Tech Republic

Published: 02 Apr 2003 09:57 BST

The entries in Listing A will export the two file systems, the LTSP root file system (/opt/ltsp/i386) and the LTSP swap files (/var/opt/ltsp/swapfiles), to any client system in the 10.0.0.0 network. Next, edit the /etc/dhcpd.conf.example, which defaults to 192.168.0.0 addressing. If you are using a 10.0.0.0 network, the /etc/dhcpd.conf file will look something like that in Listing B.

As you can see, LTSP is configured so that dhcpd will give the workstation identified with the MAC address 00:50:BA:42:F7:0E an IP address of 10.0.5.51 and a domain name of ws001.mylan.net. The configuration in Listing B also tells LTSP to boot from the kernel /tftpboot/lts/vmlinuz-2.4.18-ltsp-1. The /tftpboot prefix should not be specified as it is assumed, and the kernel name should be replaced with whichever kernel is installed. (As of the time of this writing, the 2.4.18 kernel is the latest LTSP kernel.)

If you have more workstations that will be used as thin clients, just continue to add host sections to your dhcpd.conf file. Remember to save the file as /etc/dhcpd.conf and not /etc/dhcpd.conf.example.

Finally, change to the /opt/lts/i386/etc directory and modify the lts.conf file. This is the configuration file that LTSP uses for its primary configuration. In the lts.conf file, the [Default] section is for the server itself. The SERVER keyword must be changed to the IP address of the LTSP server, and everything else can use the default entry.

Now it's time to configure the workstations. The [ws001] section is for workstation number 1; the ws001 entry specified in the dhcpd.conf file. The workstation section configures such things as which X server to use (this is relevant only if you need to use an XFree86 3.3.6 server) and the runlevel to start in. The defaults will usually work fine; in fact, you can (and probably should, to begin with) comment out all of these sections.

The lts.conf file is heavily commented and shows a few illustrations of how to configure LTSP on the client side. (For example, it shows how to configure and use a printer connected to a client machine and how to load additional modules if required.)

Keep in mind that every time this file is changed, the client system(s) will have to be restarted to see any of the changes.

Restarting the services and firing up the clients
At this point, you will need to restart a few services. On most systems, you can do this by using these commands:

# /etc/rc.d/init.d/portmap restart
# /etc/rc.d/init.d/nfs restart
# /etc/rc.d/init.d/dhcpd restart
# /etc/rc.d/init.d/xinetd restart

This will restart (or start) the portmap, NFS, dhcpd, and xinetd daemons with the new configurations. If you're using the older inetd, restart it instead of xinetd. To make all this transparent, make sure that these services will start at bootup. That can be a simple matter of adding the above commands into the /etc/rc.d/rc.local file.

If the server is already at runlevel 5 (graphical login), you should be able to start the client systems from the boot floppy. If not, you will need to start in runlevel 5 by rebooting the server or executing the telinit 5 command at the server's command prompt. This will restart the system into runlevel 5, for the graphical login. You may be satisfied with whichever display manager your Linux distribution uses by default (on Mandrake Linux, for example, it's KDM, the KDE display manager), but you can switch to a different display manager. This is somewhat system dependant, but on Mandrake Linux you can modify the /etc/sysconfig/desktop file and set the DISPLAYMANAGER equal to gdm (DISPLAYMANAGER=gdm).

Check your documentation
Refer to your distribution's documentation on how to change the display manager if you don't want to use the default.

At this point, head on over to the client system, insert your boot floppy, and boot from it. The system will use tFTP to obtain the kernel to boot from and will then use dhclient to obtain an IP address and other network information. Finally, once it has an IP address and knows a little something about the network, the system will mount the root filesystem via NFS and connect to the display manager you're running. You should find yourself quickly at a graphical login, just as you would if the system were running locally.

Key benefits
During this entire process, the only hardware used on the client system will be the CPU, memory, and the floppy drive, and you'll find the bootup and the Desktop significantly faster than on a traditional Linux workstation. Applications are run on the LTSP server, so no overhead is incurred on the client system. This also means that a lack of powerful hardware will not hamper the speed with which your applications run.

By deploying LTSP, you can use old 486 or Pentium systems as your end-user machines. The systems can be stripped so that they don't contain any hard drives, reducing the cost of those systems. (Remember, all that is required is a floppy drive.)

Maintenance costs will also be reduced. Instead of maintaining each client system, you need to maintain only the LTSP server. This can save a lot of time maintaining and configuring each system. Provided you kept copies of the boot ROM images available, the most maintenance you might have to perform on these systems will be isolated to hardware -- and perhaps regenerating the odd boot floppy.

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