PuzzleFS

PuzzleFS is a next-generation container filesystem.

Design Goals

Do computation when we want to, i.e.:
- Image building should be fast
- Image mounting/reading should be fast
- Optional "canonicalization" step in the middle
No full-tree walk required
- mtree style walks of filesystems are not necessary with clever use of overlay
- casync style generate-a-tar-then-diff is more for general purpose use where you don't want to have a special filesystem setup
Be simple enough to decode in the kernel
- A primary motivator for our working on this at Cisco is direct-mount support

OCIv2 Design doc

https://hackmd.io/@cyphar/ociv2-brainstorm

For the most part, I think this addresses things there except for two:

Explicit Minimal Metadata: this is mostly unaddressed because I didn't think about it very hard; there's no reason we couldn't just drop e.g. block devices from the spec, or at least add a note about discouraging their use. Perhaps we should make mtimes and such optional? But then canonicalization would be harder. Maybe this should be specified at image build time, sort of like the chunking algorithm is in our design.
Lazy fetch support: this seems directly at odds with the "direct mount" support at least if the direct mount code is to live in the kernel; we probably don't want to implement lazy fetch directly in the kernel, because it involves the network and lots of other stuff. However, this would be relatively easy to do using fuse, which suggests that perhaps we should choose a good language (e.g. rust :) for the implementation so that we could use the same code in the kernel and userspace, thus easily supporting this one.

TODO

explore chunking algorithms
flesh out the rest of the file type metadata
consider what "minimal" metadata might look like
play around with zstd seekable compression a bit

Implementation

format/ is the code for serializing/de-serializing the puzzlefs format
builder/ is the code for building a puzzlefs image
extractor/ is the code for extracting a puzzlefs image
mount/ is the code for fuse mounting a puzzlefs image
exe/ is the executable frontend for the above

Contributing

Contributions need to pass all static analysis.

In addition, all commits must include a Signed-off-by: line in their description. This indicates that you certify the following statement, known as the Developer Certificate of Origin). You can automatically add this line to your commits by using git commit -s --amend.

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

License

puzzlefs is released under the Apache License, Version 2.0, and is:

rvolgers / puzzlefs