I want to uniderstand in more detail how filesystems work - not how to use them, but how they are laid out on disk. Ideally, to such an extent that I could inspect a disk device with a hex editor and understand what I see - in the past I've got as far as 'inodes', but in most cases it goes a bit vague after that, and I can understand why, since there are so many different filesystems.

This is not for any purpose other than curiosity; and who knows, it might become useful. So, is there any good documentation or discussion of these subjects somewhere? Or is it back to kernel sources?


The kernel itself includes a fair amount of file system documentation, more or less detailed. The ext4 documentation includes a description of the layout (converted from the wiki a few years ago).

Other file systems are documented elsewhere, for example in XFS Algorithms & Data Structures for XFS, along with the XFS Linux wiki, or the Btrfs wiki for Btrfs. Many file systems are documented in academic papers.


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