Published at LXer:

The nullfs filesystem is a passthrough filesystem. When nullfs is mounted it - literally copies the filesystem transaction. If a file is deleted, nullfs simply transmits the information down to the lower filesystem. Conversely, if a file is created, it does the same and tacks on all of the data needed for the filesystem underneath. Why is that a good thing? Where did nullfs come from and why?. What else, if anything, is it good for? The series focuses on where nullfs comes from, how it can be leveraged, a code walk and a skeloten implementation (nearly a blind copy).

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