[Pkg-utopia-maintainers] Bug#1064457: RFP: composefs -- file system for mounting container images

[Simon McVittie]

Package: wnpp
Severity: wishlist
X-Debbugs-Cc: ostree at packages.debian.org

* Package name    : composefs
  Version         : 1.0.3
  Upstream Contact: Alexander Larsson, Colin Walters
* URL             : https://github.com/containers/composefs
* License         : GPL-3.0-or-later AND LGPL-2.0-or-later AND Apache-2.0
  Programming Lang: C
  Description     : file system for mounting container images

The composefs project combines several underlying Linux features to
provide a very flexible mechanism to support read-only mountable
filesystem trees, stacking on top of an underlying "lower" Linux
filesystem.

The key technologies composefs uses are:

  * overlayfs as the kernel interface
  * EROFS for a mountable metadata tree
  * fs-verity (optional) from the lower filesystem

---

libostree optionally uses composefs to mount OS images. At the moment it
uses a vendored copy of composefs, but there is movement upstream towards
using composefs as an external shared library and de-vendoring it. When
this happens, I will have to disable the composefs feature in src:ostree
until/unless composefs is packaged separately.

My interest in libostree is mainly for Flatpak, which doesn't use
composefs anyway, so I am not able to take responsibility for composefs as
a separate package; but I'd be fine with linking to an external composefs
maintained by someone else, if that's useful for a different use-case.