Originally Published: Thursday, 11 October 2001 Author: Rick Philbrick
Published to: enhance_articles_sysadmin/Sysadmin Page: 1/5 - [Printable]

SF-Foundries@Linux.com:: With Linux Clusters - Image is Everything!

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Most system administrators keep a sharp lookout for tools that save time or make life easier. Tasks that have recurring steps are great candidates for time saving tools, for example, the case of building or maintaining a farm of Web servers for an Internet site or a high performance cluster. If you are a system administrator with these responsibilities, SystemImager is a tool that you should take a look at, as we will in this article.

Written by Brian Elliott Finley, and a host of other contributors, SystemImager is an open source program that will automate the installation of server machines used in a cluster. It can also be used to update the content of servers or deploy software upgrades to systems en masse. The idea is to create a central repository of images on an ImageServer. Cluster machines can then be installed with or synchronize themselves to an image on the ImageServer.

The ImageServer stores the image created from one of the client machines, called the GoldenClient. The other machines can then be replicated, or autoinstalled, by booting them with special boot media. The autoinstall process partitions and formats the client's hard drive, pulls the appropriate image down, and even configures unique IP address and host name information. SystemImager works with IDE and SCSI disks, and even properly replicates software RAID and hardware RAID configurations.

Think of it this way, you supply the ImageServer with a perfect template, the GoldenClient, and it will reproduce as many identical machines as you wish. No more having to tweak RPMs or having to fuss with "tarballs" on every machine in the cluster. Just get your GoldenClient working properly, pull its image to the ImageServer, and autoinstall or synchronize the rest of the clients to match that image. The updateclient command is used to make the synchronization bit easy.

As a bonus you don't even have to be onsite to build or update the cluster machines. Let's say you have a machine at your facility on the East coast that needs to be re-installed, but you're on the West Coast. With SystemImager, you can remotely re-install that machine from the other side of the country. You can even do this securely because SystemImager supports operation over SSH. Pretty cool stuff.

What do you need to get started?

First you'll need a machine designated as the ImageServer. Make sure it has enough disk space to store the images you want pulled from your GoldenClient(s). Your ImageServer needs to have a good network connection and I've found that standard 10/100 Ethernet works fine for most sites.

Download and install the SystemImager server software on your ImageServer. You can find the software at http://systemimager.org/download/. You may need to install one or two additional packages if they are not already on your machine, but these details are explained on the download page at the SystemImager site.

The current release, 1.5.0, is tested and known to work well on Debian and RedHat based systems. I've also had success using GentooLinux as a SystemImager client. GentooLinux is very rich in features and has built-in support for the reiserfs journaling file system. The current version of SystemImager supports the ext2, ext3, and reiserfs file systems. Future versions may include support for other filesystems, such as XFS, and the next release, expected sometime this fall, will include support for any and all Linux distributions through the use of System Configurator, a tool written by Sean Dague of IBM.

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