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Ghosting is a popular process that enables a complete image of a drive or volume to be snapshotted, and then used to create a new image on one or more drives. It can, for instance, be used when a bunch of desktops need to be set up quickly with near-identical configurations.
Here, the common portion of the image is ghosted so it can be put on each unit, with no real limit as to how many times this can be done. Then, the user-specific portion of the unit's setup is added, and it's ready to use. Today's ghost imaging software enables several units to be ghosted in parallel, which increases speed.
There are many ghost imaging software packages available, both as commercial code and open source. The more sophisticated packages enable you to build a library of images that can be stored (compressed) on a large local or network drive. These images include software settings, so setup is near error-proof. It is also possible to use ghosting to clone just about everything, minus an OS, for example.
Ghosting is by far the fastest method for bringing up a new unit, whether it is a server, desktop or mobile device. It's the way vendors preload software, too.
Because settings are saved, ghost imaging software helps avoid much of the manual input required during normal, from-scratch setup. This is a real boon in the Linux world, where typing the command-line interface is very error-prone.
Ghosting has some downsides. Any existing data on the target drive can be lost, since ghosting is not incremental in nature. There is also a constraint that the source and target systems have the same hardware, though at least one ghost imaging software package -- SmartDeploy -- allows for images to be dropped onto a thin virtual machine to hide underlying hardware differences.
The nature of cloning is that it bypasses licensing tools built into installers. The result is reluctance by some vendors, including Microsoft, to support ghosted units.
Cloning has reached the cloud, with image ghosting tools available for OpenStack and the major cloud service providers. This is critical to agile instance creation, and it offers a way for certified images to be distributed to users. This certification is critical to a smoothly run cloud, keeping out rogue code and ensuring that all application and tool components are properly in sync from a revision and settings perspective.
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