Linux Terminal Server Project (LTSP) is a free and open source terminal server for Linux that allows many people to simultaneously use the same computer. Applications run on the server with a terminal known as a thin client (also known as an X terminal) handling input and output. Generally, terminals are low-powered, lack a hard disk and are quieter than desktop computers because they do not have any moving parts.
This technology is becoming popular in schools as it allows the school to provide pupils access to computers without purchasing or upgrading expensive desktop machines. If the school does not have enough computers, new thin client machines are less costly than standard computers. If the school does have enough computers but they are a few years old, they may be able to extend the useful life of obsolescent computers by converting them into thin clients, since even a relatively slow CPU can deliver excellent performance as a thin client. In addition to the possibility of getting more performance for less money by getting one high-end server and turning their existing computers into thin clients, an educational institution may also gain more control over how their students are using computing resources by switching to a thin client configuration. Some examples of distributions using LTSP are Edubuntu, K12LTSP and Skolelinux. LTSP is a registered trademark of DisklessWorkstations.com, LLC.
The founder and project leader of LTSP is Jim McQuillan, and LTSP is distributed under the terms of the GNU General Public License.[1]
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On the LTSP server a chroot environment is set up with a minimal Linux operating system and X environment.
When a client (any networked computer capable of running Linux) boots[2] from a local boot device (like a harddisk, CD-ROM or USB disk), it loads a small Linux kernel from that device which initializes the system and all of the peripherals that it recognizes. When configured for network booting (with mechanisms like Preboot Execution Environment (PXE) or NetBoot), the client first requests its own IP address and the IP address for the LTSP server via DHCP and loads the Linux kernel from a preconfigured Linux image on the LTSP server via the Trivial File Transfer Protocol (TFTP) service running on the LTSP server.
During this process the client makes a (new) DHCP request for the IP address of the LTSP server and the path to its chroot environment. When this information is retrieved, the client mounts the path on its root filesystem via either the Network File System (NFS) or Network Block Device (NBD) services running on the LTSP server.
The client loads Linux from the NFS mounted root filesystem (or NBD filesystem image) and starts the X windowing system. The client connects to the XDMCP login manager on the LTSP server. In case of the newer MueKow (LTSP 5) setup, the client first builds an SSH tunnel to the LTSP server's X environment, through which it will start the LDM login manager (on the LTSP server). From this point forward, all programs are started on the LTSP server, but displayed and operated from the client.
| Purpose | LTSP 4 | LTSP 5 (MueKow) |
|---|---|---|
| GUI Export | XDMCP | ssh -X |
| Remote login (X display manager) | KDM/GDM | LTSP Display Manager (LDM) |
| Distribution method | LTSP tarball | Native distribution |
| Root filesystem | NFS | NBD or NFS |
| Authenticating server | XDMCP server | SSH server |
The MILLE Project is funded by Canadian public agencies and school districts in the province of Quebec. MILLE means Modèle d'Infrastructure Logiciel Libre en Éducation (Free Software Infrastructure Model for Education) and is targeted at educational institutions. It is composed of four subprojects: a portal (based on uportal), an open-source middleware stack, a CD with free software for Windows/Mac and, finally, MILLE-XTERM. The base kernel of MILLE-XTERM is LTSP. The MILLE-XTERM provides a scalable infrastructure for massive X-Terminal deployment.
The MILLE-XTERM project has been completely integrated for large scale deployment of LTSP. A specific Web site and development branch have been created in 2009. One of the main differences is the integration of a central control center (web interface) that replaces the traditional "one file per thin client". It allows organizations to centrally manage thousands of thin clients and control each thin client parameter from a central location.
In order to provide good availability for the thin-clients, each of the single points of failure can be doubled in order to provide a reliable infrastructure for the thin client to boot. Those services are: DHCP server, TFTP server (initial kernel and initrd, Boot servers (root filesystem for the thin-clients) and the control center (postgresql database + web frontend).[4]
LTSP-Cluster can support Linux application servers as well as Windows application servers and provides the same level of support for both platforms: load-balancing of user sessions; and central configuration.
Application servers can be completely virtualized and then provide a virtual desktop to any remote users using the NX technology. The NX protocol can allow remote sessions to be accessed from a browser (Linux and Windows session alike) with a very low, on average, bandwidth (40 kb/s) using various operating systems (Linux, Mac, Windows).
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