Linux Thin Client Kiosks

Features

Back in the late 90's when computers had hit an all time low in price, a new phenomenon had started up. Cheap, small, and diskless "thin clients" became popular. You could buy hundreds of these small clients for just a few hundred dollars each. Since all or most of the software ran on the server each client could essentially be upgraded by just buying a better server. Sounded just like what we were looking for, or so we thought.

The Rise and Fall of the Machines

In 2000 the large university library I worked for got talked into buying a few hundred Netier NetXpress machines along with the Rapport and Citrix server software. We soon realized what a mistake we had made. Each machine had NT4 embedded on it so we still had to pay for a license for each machine, the Rapport software only worked about 50% of the time, and we spent more time rebooting our Citrix servers than using them. With computers continuing to drop in price and double in performance we soon discovered it was more cost effective to just buy a few hundred high end machines for our users every couple of years. Thus, our thin client reign was over as quickly as it had started, and the machines were all put into storage...until now.

The Revival

After seeing a few things I had done with Linux, I was asked to see if we could make Linux run on these little machines. All they had to do was run a modern web browser, limited to specific domains, which the general public could use. They were each equipped with a 24MB DiskOnChip, 64MB of RAM, an AMD 266 MHz processor, and a 10/100 ethernet card with a really old and buggy version of PXE. I had heard of the Linux Terminal Server Project and how they had Linux software to run full graphical sessions on cheap diskless hardware. With this information in hand I went forth and created some great looking clients.

Practice Makes Perfect

I decided to install LTSP 4.0 on a RedHat Linux v9.0 test machine I already had up and running. Installation was a breeze with their installation script and step-by-step manual. I could not, however, get tftp to work with these thin clients even after following instructions on various web sites about how to get Linux and tftp to work with older versions of PXE. Thankfully a ROM-o-matic boot disk with PXE support (use version 5.3.8 or better) got me back on my feet for the time being. The bootdisk downloaded the PXE image (pxelinux.0), which then downloads the kernel and initrd image and booted them onto the thin clients. The clients came up fine and looked great on these little machines. I was worried they might be a bit slow but the X Windows interface was quite responsive and really left me impressed. Since these clients were to be used in a public place they must be locked down as much as possible, unfortunately this is where Linux really seemed to lag behind. Locking the desktop down seemed almost impossible and I knew before long users would have these machines in a unworkable state. After some Google searching and Linux desktop reviews, I discovered that KDE had recently focused on a kiosk mode for their window manager.

Now for the Real Thing

After a bit of begging, I rounded up a new machine to install RedHat's Fedora Core 2. Fedora Core 2 includes KDE v3.2.2 and a nice looking desktop which would hopefully impress my boss and the general public. After installation and updates I created a new user that I could lock down using the KDE Kiosk Tool. Since we already have a Windows 2003 DHCP server running in the building, we figured it would just be simpler if we didn't have another Linux DHCP sever running beside it. However, for some reason any DHCP options sent from the W2K3 server would have three 0's appended to the end of it. Rather then search for a fix I decided to take the lazy way out and install LTSP v4.1 beta. Amazingly it fixed the problem and I highly recommend it.

DiskOnChip Observations

This probably won't apply to 99% of the LTSP group but if your trying to make your DiskOnChip boot linux, than I hope this will save you hours of work. Basically, to make a long story short, booting linux from a DiskOnChip using LILO or GRUB is more work then its worth. DiskOnChip support patches have been made but none of them ever made it into the official LILO or GRUB source. The easiest way to get these thin clients going is to use SYSLINUX and Norton Ghost. SYSLINUX is a DOS (or DOS clone) based Linux boot loader and Norton Ghost is a drive and partition cloner. I used an 8MB compact flash card with a USB reader/writer, formatted it as a FAT16 drive, loaded the kernel and initrd image from the L.T.S.P. project, copied and modified the SYSLINUX files then used Ghost to clone my 8MB compact flash drive. Then I used Ghost to write the image to the DiskOnChip on the clients.