Re: Free disk space & Netboot

On Jun 26, 2007, at 12:05 PM, Aaron Robinson wrote:

I have a quick question regarding the free disk space of a netbooted machine. I'm new to this, but have an Xserve and am trying to see how useful netboot might be.

I just turned an image created using netrestore into a netboot image using the system image utility. It boots fine, but there is only ~300MB available on the disk. this quickly runs out as applications are opened and causes issues.

Is there a step that I missed?

I think so :)

Page 17 of the System Image and SW Update PDF, located here: http://images.apple.com/server/docs/System_Image_and_SW_Update_v10.4C.pdf, states:

Shadow Files

Many clients can read from the same boot image, but when a client needs to write

anything back to its startup volume (such as print jobs and other temporary files),

NetBoot automatically redirects the written data to the client’s shadow files, which are

separate from regular system and application software.

The shadow files preserve the unique identity of each client during the entire time it is

running from a NetBoot image. NetBoot transparently maintains changed user data in

the shadow files, while reading unchanged data from the shared system image.

The shadow files are re-created at boot time, so any changes made by the user to his or

her startup volume are lost at restart.

For example, if a user saves a document to the startup volume, after a restart that

document will be gone. This behavior preserves the condition of the environment the

administrator set up. Therefore it is recommended that users have accounts on a file

server on the network to save their documents.

In other words, your netboot clients probably have a lot more than 300 MB of space, though this depends on where the shadow file is being stored. By default, it's stored on the client's local disk. It can also be stored back up on the netboot server, accessed via AFP - this is called 'diskless netboot' because it enables the netboot client to fully function without an internal HDD.

'Shadow files' are implemented within the disk images framework in Mac OS X, and are really lots of fun for all sorts of things. Here's an example of how I used shadow files to perform a spotlight index on a read-only volume, which is not supported by spotlight since it wants to store the index on the volume being indexed (in this case, a data CD): http://www.dreness.com/blog/archives/16

HTH,

-Andre

What considerations are there with using netboot images for everyday use (office apps, internet, etc) for temporary users who don't need to store files locally, but DO need to be able to use a range of applications which need to store temp files etc.

Thanks!
Aaron

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References:
	>Free disk space & Netboot (From: Aaron Robinson <email@hidden>)