A look at the Linux Terminal Server Project

Since the Linux Terminal Server Project (LTSP) came away with the Best of Show award at LinuxWorld Conference & Expo (LWCE) last week, we thought this would be a good time to take a look at the project and its status. Jim McQuillan of LTSP talked to us about the project and gave some insight into where it's going. What is LTSP? Basically, it's a package for Linux that allows low-powered thin clients to run off of a Linux server.

According to McQuillan, the project was launched in August of 1999. LTSP originated out of a project that began in 1996, to provide a solution for Binson's Hospital Supplies (BHS) that would allow access to an AS/400 for legacy applications and Unix for new applications from a single computer or terminal on each desktop. After several false starts with dumb terminals and Windows PCs, diskless Linux workstations proved to be the best solution for BHS.

Basically, LTSP is a distribution of Linux that sits on the server and is loaded by a thin client over a network using Etherboot or the Preboot Execution Environment (PXE). It sends a TFTP request for the kernel, and once the kernel is in memory, the client does an NFS mount of the filesystem on the LTSP server and a "pivot root" so that the NFS filesystem becomes the root filesystem. Then the LTSP client launches an X server to get a login back to the LTSP server. McQuillan noted that "we didn't invent this technology, it's been around for years. We just glued it together" and made it easier for people to use.

There are some vital differences between LTSP and traditional "dumb terminals" that only display applications. With dumb terminals, all processing takes place on the server. LTSP, on the other hand, makes it possible to run some applications on the server and some applications locally, so that users can run applications that might not work well running over the network or that would place a heavy load on the server. McQuillan cited Firefox as an application that would be good to run locally, or VoIP applications, which the LTSP team demonstrated at LWCE.

LTSP also makes it possible to reuse older hardware that might not be suitable for running current versions of Linux or Windows. McQuillan said that LTSP would run fine on "anything with a PCI bus and 16 MB of RAM." It also allows organizations to reduce support costs by centralizing applications and by using thin clients without hard disks -- thereby eliminating "moving parts" that fail often, and by centralizing storage.

There are a few applications that aren't suitable for LTSP. For example, McQuillan was quick to say that LTSP wasn't really appropriate for gaming. "Trying to run Quake across the network is not a pleasant experience." Other rich multimedia, such as video editing, is pretty much out as well. Also, McQuillan said that if Linux itself didn't fit well for a specific use, then LTSP was pretty much out there as well.

McQuillan said that the project does scale pretty well. The largest deployment he's worked on, the BHS deployment, runs 140 LTSP clients off of one server. He said he's also heard of setups consisting of 400 clients on a quad Opteron server.

There are some limitations for the project. McQuillan told LWN that device support is "not as robust as we'd like," but that the project is working on making things work little better. "We want you to be able to plug in a USB device and instantly, a device icon appears on the desktop...that's where we have to be."

The project is also working to make it easier to lock down the desktops so that administrators can more easily control what applications users have access to. He noted that GNOME and KDE may not be a good fit for larger environments with 50 to 100 users, because they're "fairly heavy." In those environments, McQuillan said that IceWM and XFce were good choices for lightweight window managers.

Another hurdle for LTSP is the fact that it doesn't always fit well into a distribution. Right now, LTSP provides all the "bits" that make up the thin client distribution -- glibc, the kernel, etc. However, they're working on "Project MueKow" (pronounced "moo-cow"), which will use distribution packages as much as possible rather than providing all of the bits directly. The name is a play on Microsoft's "Longhorn."

This will be showing up first in the next Ubuntu release, Breezy Badger. McQuillan said that four developers, two from LTSP and two from the K12LTSP project, went to Sydney in April to "help figure out how to integrate LTSP into Ubuntu." However, he also noted that he's eager to work with all of the distributions, not just Ubuntu.

While attending LWCE, this writer had a chance to spend some time talking to some of the other LTSP team members and looking at the technology. When using a LTSP client, there really isn't a great deal of difference between using a workstation with a local Linux installation and using LTSP.

Overall, LTSP looks like a great solution for organizations that want to save money on PCs and support costs. We're looking forward to seeing it included in Ubuntu and other distributions, which will no doubt help spread LTSP even further.

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