MILLE-XTERM and LTSP
Linux-based X terminals are well known for making computing affordable, for giving a second life to old hardware and for lightening administrative burdens. If you ever have toyed with the idea of using Linux X terminals, you are probably familiar with the Linux Terminal Server Project (LTSP), described in Figure 1. An LTSP server is perfectly suited for small workgroups or classrooms. However, in order to deploy a greater number of terminals, say thousands of them, the current LTSP model encounters scalability problems.
The main goals of the MILLE-XTERM Project are:
Centralized X-terminal management.
Enhanced user experience.
The MILLE-XTERM Project applied clustering concepts to the X-terminal infrastructure to achieve these goals.
The MILLE Project is funded by Canadian public agencies and school districts in the province of Quebec. MILLE means “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 object of the present article).
The solution entails centralizing servers in a secure, air-conditioned computer room to form a cluster of terminal servers. The cluster has four major components, as shown in Figure 2. The first is the boot server, which provides DHCP and TFTP services and serves as a base system optimized for the terminals via NFS. Next comes the configurator, which generates the lts.cfg configuration file from an SQL database. The terminal then queries the load balancer, which in turn seeks out the cluster's least-loaded application server. The chosen application server login screen then appears, and after a successful authentication, the user can start using the desktop, browser, office suite and other applications.
MILLE-XTERM relies on central file and authentication services that provide users with the same account and file on every application server. The open-source choice is NFS for users' home directories and OpenLDAP for the directory service. It also can be integrated into a Novell or Windows environment with additional configuration.
Unlike LTSP, there is no need for a separate network dedicated to terminals. They can share a LAN with other PCs. However, a reliable network infrastructure is crucial. With usual usage, each terminal generates an average of 1Mb/sec of X11 traffic. Low-end hubs should be avoided; managed switches with full-duplex capabilities really make a difference.
Unlike LTSP, each component is built from RPMs; system administrators easily can add features and local applications with standard package manager tools. The init scripts from the distribution are replaced by standard LTSP scripts. We are currently using Mandriva 2006 as the base distribution, though other distributions can be supported.
The boot server is mainly a read-only NFS server. Optionally, it can provide DHCP, TFTP and NBD swap services. The xtermroot contains a base system and an X server. With more than one boot server, it is easy to rsync the xtermroot periodically on each boot server. The terminals then boot in a uniform way, whichever boot server they use.
MILLE-XTERM supports different booting methods: CD-ROM, local hard drive, Flash disk, Etherboot or PXE. Each boot method has its advantages and drawbacks.
PXE and Etherboot rely on TFTP to transmit the initial file used for the boot process. It simplifies the deployment, as no configuration is stored on the terminal itself. However, simultaneously booting up hundreds of clients via TFTP can result in transmission errors and, consequently, boot problems.
An alternative is to use a 16MB IDE Flash disk that holds the kernel, the initrd and grub. The Flash disk is updated automatically as the terminal boots up. The disk is used only at startup and contains no moving parts.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide