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Rolling out your own Linux thin clients

  • June 16, 2000
  • By Jim McQuillan
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Help from the Linux documentation project

We had a lot of help figuring this out from the 'Diskless Nodes How-to' which we found on the Linux Documentation Project. That helped us find the Etherboot project and the Netboot project. The purpose of those two related projects are to create the bootrom image that is to be burned onto an EPROM. This was the first step in building a diskless workstation.

By following the Diskless-Nodes How-to, we learned how to set up one workstation to boot from the server. We loaded a full Red Hat Linux distribution onto the server, in a subdirectory under the /tftpboot directory. The workstation booted and ran, with all of the features of an ordinary Linux workstation. Setting up a second workstation, however, meant creating another directory under /tftpboot, and loading a full distribution for the second workstation. Fairly quickly, this method would consume a massive amount of disk space on the server.

The Diskless-Nodes Howto described a way of reducing the size of the root filesystem for each workstation, but it was a trial-and-error exercise. We decided to start from the beginning. Rather than take a full distribution and cut out what we didn't need, we started with nothing and began adding what we did need. This produced a root directory occupying only about 20 Mb of space, which was a big improvement over the approximately 110 Mb needed before. And since the workstations were all using the same operating system, they could all share the same space.

There was one problem with sharing the same copy of the operating system, however: each workstation needed to be able to write temporary files, and keep them separate from files belonging to other workstations. So we created a 4 Mb ramdisk on each workstation, mounted as its /tmp directory, to contain any transient data that needed to be written while the workstation was running. This required creating symbolic links for the /var directory and some of the device nodes in the /dev directory. This couldn't be done on the server, since the clients each needed their own /tmp directory, or they would be mixing up their temporary files with those of other workstations. Doing this enabled us to mount the root filesystem in Read-Only mode. Since none of the workstations would be writing to the root filesystem, they could all share one root filesystem.

Cool-running workstations

We still needed to convince Binson's that this would work. With their approval, we launched a pilot project. From the point of conception to the initial installation of the first 11 workstations took about three weeks. It didn't take long at all for management at Binson's to see that the diskless workstations were going to work. They quickly gave the go ahead to install the other 24 workstations.
"The really beautiful thing is that the workstations require no maintenance at all. "

Installation turned out to be really easy. Each workstation only required an entry in the /etc/hosts file, mapping a workstation name with an IP address, and an entry in the /etc/bootptab file, mapping its network card's MAC address (a number which uniquely identifies each network card) with its IP address. That's it! Two records added for each workstation.

We could easily hand the job over to a couple of staff members who didn't need to know anything at all about Linux. They could just roll out the workstations, one right after another.

The workstations we used were brand new 166 Mhz Pentium machines with a video card, 32 mb of RAM and a network card with a bootrom chip. As it turned out, the Pentium processor was more processing power than the users needed, but this was the least expensive processor we could get at that time.

Binson's employees are now happily using the workstations to reach applications such as the patient, insurance, and inventory databases on the AS/400 and SCO servers. And the managers at Binson's have been so impressed with the diskless workstations, they began finding more uses for them. They soon ordered 35 more, and put them into production just as easily. They even began replacing existing PCs with diskless workstations running StarOffice for word processing and spreadsheets, and Netscape Communicator for e-mail and Web browsing. Today, the company has 100 diskless Linux workstations, all booting from one single Pentium II 400 Mhz server.

The really beautiful thing is that the workstations require no maintenance at all. By removing all of the moving parts, and running a fairly low-end processor, the internal temperature of the workstations remains very low, resulting in an extremely low failure rate.

True spirit of the open source movement

We realized that the problem that we had solved for Binson's was something that many other people around the world were facing. And, because we had relied upon several existing open source projects, the only logical thing to do was to offer our solution to the world.

In August 1999, we created the Linux Terminal Server Project (LTSP). We registered the domain name, built the Web server, recruited a bunch of friends, created the mailing lists, packaged the software for download, recruited more friends, wrote the documentation and made the announcements on LinuxPR, Freshmeat.net, and the Comp.Os.Linux.Announce news group (COLA). Almost immediately, the traffic started coming. Lots of people downloaded the documentation and the packages and began playing with the technology.

It only took about 24 hours before people were sending us patches and offering to contribute to the project. This was the true spirit of the open source movement. We were impressed.

Since that time, we've released several updates, given talks at major Linux and open source trade shows, written a couple of articles and shared experiences with some wonderful people all over the world. Over 12,000 people have downloaded the core packages, while more than 20,000 people have downloaded the documentation. We've had reports that thousands of diskless workstations running the LTSP software have been deployed in all parts the world.

The combination of low cost and ease of maintenance seems to make diskless Linux workstations particularly attractive to schools, and small to medium businesses. We think that it is just a matter of time before larger corporations see its advantages as well. For many organizations, it has clearly put new life into older PCs that were deemed "Not powerful enough to run anything useful, like Windows".

Whether you are involved in a project to deploy new hardware or trying to reuse existing hardware, the LTSP could be just what you need to keep costs down and user satisfaction up.

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