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How To: Build A Read-Only Linux System

Jan 30, 2009, 01:33 (0 Talkback[s])

"There are a couple of different approaches to making a Linux system read-only. Unfortunately, it is usually not as simple as using a conventional filesystem mounted with the read-only option. Many programs assume that at least some parts of the system are writable. In some cases, these programs will fail to run correctly if this turns out not to be the case.

"I'll outline here what I think is the best approach for most applications. It is similar to that taken by the current generation of live CD distributions.

"Live CDs typically have read-only access to a root filesystem, which is often compressed into a single file to be mounted later using a loopback device. Knoppix broke new ground with its use of the cloop filesystem for this purpose. More recent live distributions take this a step further by using a union filesystem to make the root filesystem writable. This approach is quite useful for our purposes, as well."

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