Deploying Images in Objective-C

Drawer Data Matrix in Objective-C Deploying Images

Deploying base images to hundreds of machines can be extremely hard on bandwidth and on the server hosting images. Multicasting can relieve the stress by offloading the heavy lifting to the switching infrastructure, and there are a number of solutions you can use for this type of image deployment, including DeployStudio and NetRestore (both use asr as a back end protocol). With multicasting, the server provides a single stream of imaging data to which client machines can subscribe and then read. In such a scenario,

the server constantly streams the block data of the image over the network. On reaching the end of the image, the server starts re-streaming from the beginning. After subscribing to the stream, clients begin laying down data to their internal drives according to the current progress of the stream. A client will continue to write data until it has completed a full loop of the stream. A multicast deployment becomes essential as deployment numbers scale; even a Gigabit Ethernet connection will become fully saturated after about 20 concurrent unicast restore streams. Solutions capable of multicast deployment in OS X include the Apple-provided ASR and NetInstall tools, two solutions that have been available for a long time. Over the past few years, a number of third-party solutions to help deal with imaging for Mac OS X have also emerged. These range from free alternatives, such as NetRestore (for 10.4 and below) and DeployStudio, to proprietary solutions that come at a cost, such as the Casper Suite and LANRev. There are also a number of solutions that you can use to extend features of Windows- or Linux-based imaging solutions, such as Altiris and KACE. Which is the best mass-deployment package Whichever best automates the aspects of a deployment that your organization considers most important (and, as a result, provides the best return on investment in by cutting hours involved in repetitious pre- and postflight imaging tasks). For example, the Casper Suite is very popular in environments implementing ITIL (Information Technology Infrastructure Library) because it takes into account a number of ITIL best practices, allowing for both deployment and long-term management of approved fixes and software. But many environments less-complex needs that an admin can satisfy simply by laying down an image, often opting to use very cost-effective tools such as NetRestore, ASR, and DeployStudio. Most of these solutions support both unicast and multicast image deployment. While multicasting definitely is preferable in large environments, implementation isn t always possible due to increased network management complexity, particularly in larger, highly segmented networks. If this is an issue, either for technical or political reasons, unicast deployment may be the reality you face. In such cases, deploying site-, building-, or subnet-specific image servers may be desirable to more evenly distribute network load. Likewise, you ll want to perform deployments strictly during off-hours to prevent them from saturating your network backbone.

Earlier in this chapter, we described how to create an image. If you followed the instructions in the previous section, that was a monolithic image----likely one with no automation in it except for maybe a quick script to sanitize the system. Every computer that gets the image will have a unique computer name and should be named prior to being put into production. We ll be deploying the image over FireWire, which is a unicast method and limited to one computer at a time. To roll out this image, you can again use Disk Utility, located in /Applications/Utilities. Simply click on the destination volume for your image and then click on the Restore tab, as shown in Figure 6-6. Here you ll see two fields, Source: and Destination:. Click on the Image button to select the DMG file you created in the