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Desktop Linux: Think Thin

The potential killer app for Linux

Thin-client computing is alive and well...and thriving in early-adopter environments. In this article, Dr. Migration explains why thin-client systems are showing up everywhere from POS applications to classrooms, and why you might want to consider a thin-client solution for your own organization.

Almost every desktop computer user today is familiar with the PC computing model in which user applications are executed on the local PC and data is stored on the local hard drive. This type of computing model is sometimes referred to as thick-client computing when extended to the network with file or print serving.

An alternative to this model is thin-client computing, in which applications are executed on the server and information is redisplayed over a network to "dumb terminals" or "thin clients" that offer input and video display capabilities. This model was necessary when computer-processing power was expensive and there was a need to share expensive mainframe computers. However, as computer hardware prices fell the PC became ubiquitous and, subsequently, the economics changed, allowing many users access to computers as an everyday part of their jobs and even in their homes.

Despite the rise of the inexpensive x86 commodity PC, thin-client computing is still alive and well for many who use client/server applications every day by virtue of the World Wide Web. Web services allow many applications that execute on the server to be redisplayed back to the PC via a Web browser. In addition to the Web, there are many other client/server applications that are truly thin client. Linux, which is a multi-user operating system, is ideally suited to power these thin-client solutions and being superbly suited to operate as a client OS for thin-client computing applications because it can provide the necessary thin-client tools in a small and efficient footprint.

What Does a Thin-Client Network Look Like?
A thin-client network has at least three components: server (or terminal server), network (preferably Ethernet), and thin client (software and/or hardware).

  1. Server or terminal server: The Linux operating system has been developed as a multi-user system with the capability to serve virtual terminals, hence the terminology "terminal server." Therefore, many individual users can log into the server and use it simultaneously. Individual user configurations can be limited to single applications or a full-blown desktop computing environment. Tools exist in most Linux distributions that allow administrators to limit permissions and grant access to certain applications only. Permissions can be controlled at a user level and users can be included in groups that have common traits and have like permissions and applications.
  2. Network: The network requirements for thin-client GUI implementations depend on a reasonable amount of bandwidth and low latency to be suitable for everyday use. In a corporate environment a 10/100 LAN that operates optimally with adequate bandwidth should serve well. Server sessions can be streamed to clients via the X.11 protocol and redisplayed by an X server in these optimal environments. However, in less ideal situations, redisplay technologies can be utilized to improve performance by compressing redisplay data and limiting the screen refresh and redraw rates. Technologies like Tarantella (www.tarantella.com) and Citrix (www.citrix.com), as well as the popular open source solution Tight VNC (www.tightvnc.com) offer such capabilities.
  3. Thin client: Thin-client software can reside on a PC or on a device designed for thin-client applications. These solutions normally provide a mechanism for video redisplay and input. Clients are normally stateless so data and configuration data are limited or nonexistent. Therefore, if the client is damaged the loss is only in the operating software or hardware - data and computing environments are preserved. Also, since information no longer resides locally, everyday occurrences like employee moves and coffee spilled on machines are less disruptive. Figure 1 shows a simple schematic for thin-client computing. Note that the processing resides on the server and thin clients redisplay video and relay keystrokes and other information over the network. Also, it's possible to run thin-client software on thick-client PCs.

Why Go Thin Client?
It's very easy to make a case for thin-client computing from a systems management standpoint. Environments are easily standardized, and costs for such systems can be considerably lower than for traditional PC environments. The advantages of the thin-client model are numerous. Following are some common benefits that organizations might find in thin-client computing.

Reduced Cost of Desktop Computing Hardware
Thin-client PCs only serve video and provide input functions in most cases. Because technology in these areas doesn't obsolesce as quickly as in the processor and memory world, the useful life of these devices can be many times longer than that of a traditional PC. Also, because storage is pooled on the server CPU, memory and storage can be leveraged over a pooled user base. Resources that were once dedicated to single users are now shared among a group. For example, when a user is on a break, or "off the network," a second user can take advantage of those extra cycles. Mice and keyboards, monitors, and video cards can have a useful life that is much longer than that of the rest of the PC.

Centralized Administration
Rather than process updates across individual desktop computers, administrators can process system-wide updates on the server. Updating software for many users can be taken care of with one simple installation. To evaluate how valuable this could be to your organization, speak to your IT help desk and ask them how much time they spend on the "SneakerNet." The "SneakerNet" refers to the time they spend walking around looking for cubicles, to fix user PCs. Not only do they need to find the cubicle, but also they need to bring parts, software, and tools to fix the PC. Thin clients are very low maintenance and most of the time formerly spent traveling to and from cubicles can be dedicated to improving the operating environment rather than maintaining it. If something does break, help desk personnel can open the user session locally at their desk, make the fix, and then allow the user to reacquire their session at their desk - no travel time required.

Portability of Computing Environment
Since there is little or no personal data kept on thin-client devices, users can pull up their computing environment from any network-connected thin-client workstation. On the Sun Microsystems campus, users simply carry their employee ID and embedded smart card with them and they can pull up their computing desktop at any Sun Ray workstation (www.sun.com/sunray) on campus, making it possible for employees to travel among connected campuses and pull up their work environment anywhere, from a cubicle to a conference room, which makes them much more productive. Sun also claims that they can more efficiently use space because of workstation mobility and sharing abilities.

The same flexibility Sun illustrates on their campus can be applied to telecommuting empowered by secure WAN redisplay solutions like Citrix and Tarantella. Workers at home can use thin-client software on top of their PC securely, without the need to maintain a corporate laptop that can take abuse during the commute to and from work. Helping home users maintain their work computing environments can be very difficult for corporate IT departments. Maintaining the environment in the data center limits the problems associated with remote PC maintenance.

High Availability
In businesses where employee downtime has immediate and severe effects, high-availability solutions are key. In an inbound sales center, for example, it's important that order processing and billing systems are highly available and rendundant. Desktop models in contrast are not redundant and have many points of failure. During the time that employees' computers are down they lose productivity. This isn't always obvious, but in many businesses employee downtime due to IT troubles can be much more expensive than the cheap IT systems on which the business saved a relatively small amount of money.

Rapid Deployment
Imagine the case of a large florist whose normal business increases tenfold for Mother's Day, or a large catalog company that quadruples its workforce for the Christmas holiday season. Rapid expansions like this can cause IT headaches. A relatively pain-free solution would be to simply add user accounts to a server farm and plug thin-client devices, such as Neoware's Eon (www.neoware.com/products/eon/preferred.html) or Sun's Sun Ray, into Ethernet ports in a cubicle versus installing operating systems and software on hundreds or thousands of PCs. Or in the case of disasters, for example, Hurricane Isabel in the eastern U.S. this past fall, if work environments were housed safely in hardened telecom facilities, displaced workers could simply go to a new network-connected facility while flood waters receded and infrastructure in the affected areas was repaired. In each case installation of new systems could be completed in minutes rather than a few days.

Standardization and Implementation of Standards
Because the computing environments are "virtual," it's easy to standardize the configuration so that all users have the same environment. This is valuable for training purposes as well as in accounting for computing systems and software.

These are all compelling arguments for deploying a thin-client environment. Even taken singly, each one has a common motivating factor: it could and would save organizations money. This is especially true in environments with large numbers of task-based workers who have relatively modest computing needs.

Thin-Client and Desktop Migration Strategy
Many organizations that are looking at migrating to Linux on the desktop still think in terms of fat-client PCs. However, in the case of a desktop migration in which the whole operating system changes it may be advantageous to deploy via a thin-client model. Not only does this model offer a relatively easy way to stage and implement a new desktop environment, it also frees users from their desks. Imagine developing a presentation with supporting documents in your office, then walking to a conference room with a thin-client terminal to pull up that same information - without carrying a laptop or CD. This model obviously offers flexibility within the office and could also be extended to any Internet terminal so that employees could telecommute easily or do remote-site presentations for clients, partners, and other employees.

Trial and Pilot Programs
Thin-client computing trials need not permanently change any PC other than the server you use to serve Linux. You could simply allow Windows users to receive their Linux sessions on Windows. That way they can dip their toes in the waters of Linux without giving up their Windows security blanket. There are many ways to do this without making irrevocable changes to your infrastructure. Consider the following tactics for a "trial separation" from Windows.

Live CD Trials
In my first LWM column (Vol.1, issue 1, www.linuxworld.com/story/33889.htm) I discussed Knoppix (www.knopper.net/knoppix), a bootable Linux CD that is an excellent way to get your feet wet with Linux. Before uprooting and replacing existing desktops you may want to consider the wave of bootable Linux CDs with a collection of GNU/Linux software, automatic hardware detection, and support for many graphics cards, sound cards, SCSI and USB devices and other peripherals to evaluate. These CDs can be booted from your existing CD drive and run Linux on your existing PCs without damaging your existing installations. Also, many of them have the ability to access your existing file system in read-only mode. Three good options are Knoppix (www.knopper.net/knoppix/index-old-en.html), LindowsCD (www.lindows.com/lindowscd_info.php), and SUSE Linux for i386 Live-Eval (www.suse.com/us/private/download/suse_linux/index.html). These live trial CDs are designed for running thick-client models but also offer the necessary software to temporarily convert desktops with a method for rollback.

X Windows on Windows
Herman Verkade's article "Cross-Platform Integration with X Windows" (LWM, Vol. 1, issue 1, www.linuxworld.com/story/33902.htm) explains how to run Linux applications on your existing Windows PC. This is also a good way for those not yet willing to commit to Linux, or those just looking for the best of both worlds, to obtain cross-platform integration. Linux applications can be integrated into your existing infrastructure easily and at little or no software licensing costs, and once again all applications are housed on the server, leaving current PC and infrastructure in place. Linux simply augments this environment.

Phased-in Approach to Migration
It's not practical for most organizations to take a giant leap to a new operating system. However, there will probably be inflection points in the enterprise software life cycle that will make phased-in migration more appropriate. Examples of transition opportunities to start deploying Linux thin-client desktops may include the addition of new employees, the end of useful life for thick-client workstations that could be easily converted to thin clients, or the time of renewal for your existing operating system. In some cases it may not be necessary or practical to switch all of your systems at once, but by introducing Linux, even gradually, into the desktop computing mix you begin to add a powerful and frugal tool to your infrastructure.

Recycle: It's Good for Your IT Environment
One very frugal approach to thin-client computing is the recycling method. This method works well when repurposing machines that have outlived their useful life as a desktop PC. Despite having lower CPU speeds, less memory, and limited storage space, these machines are far from useless. The LTSP - Linux Terminal Server Project (www.ltsp.org), an open source community project, helps breathe new life into what may have been thought of as useless hardware. This organization offers a blueprint for repurposing aging PCs into thin-client devices. They also outline how you could configure a terminal server to serve desktop environments. Granted, there will still need to be some investment in servers to drive the LTSP, but in comparison to a thick-client model, it's considerably cheaper than upgrading all the desktop PCs in environments with five or more PCs and task-based users.

Data and Application Replacement
Before making arrangements to move from one platform to another, it's important to inventory which data needs to moved and which supporting applications need to be available to the desktop computer user base. No matter what your strategy, either straight migration or phased movement from platform to platform, it's important to make sure that you have a plan to protect your infrastructure. One good first step is to migrate local PC data to file servers. A good Linux solution for Windows users would be a Linux server running Samba (www.samba.org), which can appear just like a Windows file server to the clients. Once data is uploaded it's just as easy to retrieve the information from the Linux thin client.

An open source, thin-client model offers a multitude of benefits from an administration and software licensing perspective, but on the other side, the aspect that presents the most risk for many companies is the disruption caused by an OS migration. Retraining staff on a new suite of applications is the factor that has to be weighed most carefully. My recommendation for an organization that's making the choice to migrate to open source desktop environments would be to start using open source applications on their legacy OS first. By starting to use OpenOffice or StarOffice in place of their existing office suites users will cut down on the learning curve afforded by a brand new cast of applications and OS later on. By gaining familiarity with these suites in a comfortable setting (existing desktop environments) users can become familiar with applications that will be their sole choice down the road. Also, the use of Mozilla (www.mozilla.org) instead of Microsoft's Internet Explorer may be a wise choice. Not only does Mozilla offer nearly all the same features, it also offers some additional value in its tab-based browsing and pop-up blocker. E-mail clients are quick and easy switchover candidates. Not only are Linux e-mail clients fairly intuitive for users, IT staff will be thankful for the decreased vulnerability to Microsoft Outlook and Windows viruses that results from using Linux solutions. Additionally, for those applications that you have already invested in for Windows there are "bridging" technologies that allow you to run Windows applications on Linux. Codeweavers' CrossOver Technology (www.codeweavers.com) and NeTraverse's Win4Lin (www.netraverse.com) allow applications to run on Linux in the cases where retraining or application availability are limiting factors.

'Sweet Spots' for Thin-Client Technology
Early adopters of thin-client computing are those who have relatively modest computing needs in terms of their desktop computing complexity. They typically need their systems to be highly available, cost-effective, and mobile. The following functional groups and organizations meet this profile.

Point of Sale (POS)
One area where thin-client computing has seen success is in Point of Sale (POS) applications. POS is ideal for thin-client computing because retail is often required to expand and contract with seasonal shopping. Additionally, it's important that these applications are highly available because down time can cause sales losses. Apropos Retail Systems (www.aproposretail.com) in Bellevue, Washington, understands this and has converted their line of POS systems to Linux. They chose Linux as their preferred platform despite being located miles from Microsoft's Redmond campus. Levin Furniture (www.levinfurniture.com), a western Pennsylvania furniture retailer, is implementing thin-client technologies because they like the idea of mobile desktops that can run their Java-based sales applications from any workstation in their showroom. This makes it easier for them to speak to customers but still pull up SKUs and order information from their warehouses.

Call Center
Thin-client computing excels in call centers. Often call center employees have specific repetitive tasks. Also, they typically have large numbers of users with identical needs. Many times they require workstations to be shared and used by employees who may sit in a different seat every day. Because of this need for mobility it's advantageous for them to have a customized but mobile desktop. In a thin-client environment they could simply log in from any desktop and have access to all the tools they need to do their job.

For all the reasons that thin-client computing makes sense in the call center it makes sense in schools. Computer users, or in this case students, share workstations among as many as seven or eight users a day. Linux has robust user management systems that can be used to create individual virtual desktops for students or to create sessions that rebuild themselves automatically as classrooms turn over groups of students. In the Netherlands, systems integrator Siceroo has helped numerous schools provide this type of infrastructure through Linux and Sun Rays. Each student gets a smart card that holds his or her authentication data. Their computer labs are equipped with Sun Ray thin clients. When students arrive at class they can start their work at any stateless Sun Ray workstation. They can then remove their smart card and walk to the teacher's desk and pull up their work via a similar thin-client terminal. Schools who are often the beneficiary of donations of older computing equipment are ideal candidates for the LTSP or an offshoot of this program, which is the K-12 LTSP (http://www.k-12ltsp.org) for schools.

Branch Infrastructure
Branch infrastructure with many small offices where an on-site IT person makes little sense could benefit greatly from a thin-client configuration. Thin clients employed at the local branches would have fewer "moving parts" that might break, while complex desktop environments could be maintained in the data center and distributed over the wire to remote offices. Additionally, a standard server and user application configuration makes it easy to create uniform implementations that can be easily installed and maintained across a large number of branches. This is a cookie-cutter and plug-and-play model that is becoming popular in retail organizations. The fact that the Linux server license is free also makes it much more economical to replicate across hundreds or thousands of "small" servers, while a Microsoft server license would make such a strategy expensive.

Thin-client computing is an excellent solution for many environments. In my opinion it has the potential to be the killer application for Linux because the architecture is flexible and relatively painless to implement using a phased approach. The ideal candidates for early adoption have relatively modest desktop computing needs with large numbers of task-based workers. To date, the lack of a thin-client migration strategy or experience base, both of which are necessary to offer a quick and efficient desktop implementation, is one reason for the limited Linux desktop adoption. Thin-client computing is a practical approach for those looking for less volatile migration paths. Terminal servers offer a way to stage and cautiously deploy desktop environments. Additionally, the thin-client architecture adds value in the form of mobile, or device-independent, computing and reduced administration.

Case Study: Thin-Client Solutions in Schools
Siceroo (), a systems integrator in the Netherlands, implements IT solutions in primary and secondary schools. Their mission is to provide cost-effective solutions for educational institutions throughout their country. Schools need access to education applications written for Windows. However, they are limited financially, and by a lack of localized technical staff. Siceroo looked at a number of thin-client computing solutions, including Microsoft-based Citrix, to solve these problems. However, Linux teamed with bridging technology in the form of Win4Lin Terminal Server () made a Linux thin-client solution the logical choice.

Zodiac is Siceroo's answer to the schools' needs for a low-cost, dependable computing solution. Zodiac is Siceroo's thin-client approach to desktop computing, which works well because it not only offers a highly available, scalable desktop environment but also allows systems to be remotely managed. For primary schools this is a great advantage as system management problems are a limiting factor for not integrating computing solutions into daily lessons.

System Architecture
Students in the Netherlands utilize a number of educational applications written for Windows. Zodiac delivers these applications via a thin-client computing model. Windows applications are deployed from a central Linux server that has been enabled to run Windows applications thanks to NeTraverse's Win4Lin Terminal Server. The students' workstations are Sun Ray thin clients, which allow students to access their work via a smart card. This smart card lets them pull up their work at any Sun Ray desktop, be it at a workstation or their teacher's desk.

Typical Implementation
Ivar Janmaat, chief technology officer of Siceroo, is responsible for the deployment of these systems in Dutch schools. A typical school's configuration consists of a single Linux server, together with a Sun Ray setup for 15–50 concurrent users. Smart cards are used to maintain Linux desktop state on the Sun Rays, allowing students and teachers to instantly enable sessions on different clients by simply transferring the smart cards.

Windows on Linux the Best Choice
Siceroo did not come to the decision to use a Linux solution lightly. They investigated a number of different architectures, including Microsoft Citrix, but Linux-based NeTraverse Terminal Server was clearly superior because of the following:

  • Good audio/video/animation synchronization.
  • Good video performance. 2D panorama views in Encarta and 3D CAD/CAM applications are acceptable under Win4Lin; with Citrix this is unusable and slow.
  • Almost full Windows 95/98 compatibility is important for educational software written for Win3.1/95/98, which will not run on Windows NT or 2000 and thus not on a MS Windows Terminal Server.
  • Easy distribution of software utilizing Linux scripting tools.
  • The ability to install plain windows without an application. Schools can then install their own applications. Citrix doesn't allow this. Citrix Metaframe/MS terminal server is a shared environment, so supported applications could be corrupted by the installation of some software.
The solution has become a model for how schools with very limited resources, a large number of users, and shared workstations can deploy affordable computing systems. Siceroo continues to convert schools throughout the Netherlands to this model as it best utilizes their IT budgets without sacrificing their need for educational applications.

More Stories By Mark R. Hinkle

Mark Hinkle is the Senior Director, Open Soure Solutions at Citrix. He also is along-time open source expert and advocate. He is a co-founder of both the Open Source Management Consortium and the Desktop Linux Consortium. He has served as Editor-in-Chief for both LinuxWorld Magazine and Enterprise Open Source Magazine. Hinkle is also the author of the book, "Windows to Linux Business Desktop Migration" (Thomson, 2006). His blog on open source, technology, and new media can be found at http://www.socializedsoftware.com.

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S Ravindran 05/11/04 03:29:45 AM EDT

We want to use IBM PPC405 based (Linux) STBs as thin clients with backend computing--to help bridge digital divide in India---is there an approach in this area?

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