845dc65196
Quoting Dan Nicholson in <https://github.com/ostreedev/ostree/pull/330#issuecomment-245499099> mtime of 0 has been the semantics of ostree deployments from basically the beginning of the project. We (and others, see flatpak/flatpak@b5204c9) rely on that fact when generating trees. In particular, this affects caches that use the mtime of the associated file or directory to determine if the cache is valid. By arbitrarily changing the mtime of the files to something else, all the caches we setup in the build are now invalidated. Preseeding caches is really important to the user experience as it avoids having the user wait while they're regenerated on first run. Now, we could change our build infrastructure to preset all the mtimes to 1 to match this change, but what does that do for our existing users who are on an ostree that deploys with mtimes of 0? We could just revert this change at Endless (and the associated one in Flatpak), and that would be fine for our users. However, if we point non-Endless users to our apps, they'll have the great experience of waiting 10 seconds the first time they launch it while the fontconfig cache is rebuilt unnecessarily. Closes: #495 Approved by: jlebon
OSTree
New! See the docs online at Read The Docs (OSTree)
OSTree is a tool that combines a "git-like" model for committing and downloading bootable filesystem trees, along with a layer for deploying them and managing the bootloader configuration.
OSTree is like git in that it checksums individual files and has a content-addressed-object store. It's unlike git in that it "checks out" the files via hardlinks, and they should thus be immutable. Therefore, another way to think of OSTree is that it's just a more polished version of Linux VServer hardlinks.
Features:
- Atomic upgrades and rollback for the system
- Replicating content incrementally over HTTP via GPG signatures and "pinned TLS" support
- Support for parallel installing more than just 2 bootable roots
- Binary history on the server side (and client)
- Introspectable shared library API for build and deployment systems
This last point is important - you should think of the OSTree command line as effectively a "demo" for the shared library. The intent is that package managers, system upgrade tools, container build tools and the like use OSTree as a "deduplicating hardlink store".
Projects using OSTree
rpm-ostree is a tool that uses OSTree as a shared library, and supports committing RPMs into an OSTree repository, and deploying them on the client. This is appropriate for "fixed purpose" systems. There is in progress work for more sophisticated hybrid models, deeply integrating the RPM packaging with OSTree.
Project Atomic uses rpm-ostree to provide a minimal host for Docker formatted Linux containers. Replicating a base immutable OS, then using Docker for applications meshes together two different tools with different tradeoffs.
flatpak uses OSTree for desktop application containers.
GNOME Continuous is a custom build system designed for OSTree, using OpenEmbedded in concert with a custom build system to do continuous delivery from hundreds of git repositories.
Building
Releases are available as GPG signed git tags, and most recent versions support extended validation using git-evtag.
However, in order to build from a git clone, you must update the submodules. If you're packaging OSTree and want a tarball, I recommend using a "recursive git archive" script. There are several available online; this code in OSTree is an example.
Once you have a git clone or recursive archive, building is the same as almost every autotools project:
env NOCONFIGURE=1 ./autogen.sh
./configure --prefix=...
make
make install DESTDIR=/path/to/dest
More documentation
New! See the docs online at Read The Docs (OSTree)
Some more information is available on the old wiki page: https://wiki.gnome.org/Projects/OSTree
Contributing
See Contributing.