Linux Terminal Server Project
Encyclopedia
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
.
environment is set up with a minimal Linux operating system and X environment
.
When a client (any networked computer capable of running Linux) boots
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.
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).
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).
Free and open source software
Free and open-source software or free/libre/open-source software is software that is liberally licensed to grant users the right to use, study, change, and improve its design through the availability of its source code...
terminal server
Terminal server
A terminal server enables organizations to connect devices with an RS-232, RS-422 or RS-485 serial interface to a local area network . Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication...
for Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
that allows many people to simultaneously use the same computer. Applications run on the server with a terminal known as a thin client
Thin client
A thin client is a computer or a computer program which depends heavily on some other computer to fulfill its traditional computational roles. This stands in contrast to the traditional fat client, a computer designed to take on these roles by itself...
(also known as an X terminal
X terminal
In computing, an X terminal is a display/input terminal for X Window System client applications. X terminals enjoyed a period of popularity in the early 1990s when they offered a lower total cost of ownership alternative to a full Unix workstation....
) 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
Edubuntu
Edubuntu, also previously known as Ubuntu Education Edition, is an official derivative of the Ubuntu operating system designed for use in classrooms inside schools, homes and communities....
, K12LTSP
K12LTSP
K12LTSP is a modification to the Centos operating system with the Linux Terminal Server Project packages integrated into it. It's designed to be easy to install and configure. K12LTSP is an off-shoot of the Linux in School Project ....
and Skolelinux
Skolelinux
Skolelinux is an operating system intended for educational use and based on Debian .Skolelinux is a free and open source software project founded in Norway, now supporting all languages present in Debian...
. 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
GNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
.
The LTSP client boot process
On the LTSP server a chrootChroot
A chroot on Unix operating systems is an operation that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot name files outside the designated directory tree. The term "chroot" may refer to the chroot...
environment is set up with a minimal Linux operating system and X environment
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
.
When a client (any networked computer capable of running Linux) boots
Booting
In computing, booting is a process that begins when a user turns on a computer system and prepares the computer to perform its normal operations. On modern computers, this typically involves loading and starting an operating system. The boot sequence is the initial set of operations that the...
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
Network booting
Network booting is the process of booting a computer from a network rather than a local drive. This method of booting can be used by routers, diskless workstations and centrally managed computers such as public computers at libraries and schools...
(with mechanisms like Preboot Execution Environment
Preboot Execution Environment
The Preboot eXecution Environment is an environment to boot computers using a network interface independently of data storage devices or installed operating systems.PXE was introduced as part of the Wired for Management framework by Intel and is described in the specification The Preboot...
(PXE) or NetBoot
NetBoot
NetBoot is a technology from Apple which enables Macs with capable firmware to boot from a network, rather than a local hard disk or optical disc drive. NetBoot is a derived work from the Bootstrap Protocol , and is similar in concept to the Preboot Execution Environment...
), 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
Trivial File Transfer Protocol
Trivial File Transfer Protocol is a file transfer protocol known for its simplicity. It is generally used forautomated transfer of configuration or boot files between machines in a local environment....
(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
Mount (computing)
Mounting takes place before a computer can use any kind of storage device . The user or their operating system must make it accessible through the computer's file system. A user can access only files on mounted media.- Mount point :A mount point is a physical location in the partition used as a...
the path on its root filesystem via either the Network File System (NFS) or Network Block Device (NBD)
Network block device
In Linux, a network block device is a device node whose content is provided by a remote machine. Typically, network block devices are used to access a storage device that does not physically reside in the local machine but on a remote one...
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
Secure Shell
Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...
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 GNOME Display Manager GDM provides a simpler to use alternative display manager for the X Window System's XDM.The X Window System by default uses the XDM display manager. However, resolving XDM configuration issues typically involves editing a configuration file. GDM allows users to customize or troubleshoot settings... |
LTSP Display Manager (LDM) |
| Distribution method | LTSP tarball | Native distribution |
| Root filesystem | NFS | NBD |
| Authenticating server | XDMCP server | SSH server |
Massive deployment with MILLE-Xterm
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.MILLE-XTERM evolution : LTSP-Cluster
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).
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
NX technology
NX technology is a computer program that handles remote X Window System connections, and attempts to greatly improve on the performance of the native X display protocol to the point that it can be usable over a slow link such as a dial-up modem...
. 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).
See also
- Diskless Remote Boot in Linux: similar booting system that can use local hardware resources
- Multiseat configuration
- RULE ProjectRULE ProjectRULE is a project that aims to use up-to-date Linux software on old PCs , by recompiling and changing some code to recent programs in order to make them use less resources so they can run conveniently....
- Sun RaySun RayThe Sun Ray from Oracle is a stateless thin client solution aimed at corporate environments, originally introduced by Sun Microsystems in September 1999...
- Time-sharingTime-sharingTime-sharing is the sharing of a computing resource among many users by means of multiprogramming and multi-tasking. Its introduction in the 1960s, and emergence as the prominent model of computing in the 1970s, represents a major technological shift in the history of computing.By allowing a large...
- VT100VT100The VT100 is a video terminal that was made by Digital Equipment Corporation . Its detailed attributes became the de facto standard for terminal emulators.-History:...
- Windows MultiPoint Server