This package contains the implementation for handling both the packaging and distribution of Unikraft unikernels via the Open Container Image (OCI)'s Image Specification.
At a high-level, this is done in order to ease distribution of pre-built unikernel images using existing infrastructure. More precisely, the specification is adopted with several well-known annotations and practices to ensure consistency and compatibility with Unikraft unikernel images which are packed into an OCI image format.
The OCI Image Specification allows for the declaration of artifacts in a hierarchical fashion. The top-most element is an index which contains a list of manifests. Each manifest in KraftKit's case is a pre-built unikernel image along with accompanying root filesystem.
There are currently two supported backends for using and manipulating OCI images in KraftKit:
directory(default) handles the representation of the OCI Image in directory format;containerdwhich requires configuration in the KraftKit config file and uses containerd's content storage system.
kraft pkg --name helloworld:latest --with-kconfig --plat qemu
In the directory implementation, the representation results in the following artifacts on the host system:
/root/.local/share/kraftkit/runtime/oci
├── configs
│ └── sha256
│ ├── 9530779d911fc36a50e156d36379d2e4d59eb259f28fba2311a80845a11988ec.json
│ └── fe5f6abe40068df5d5e98a08dc2f697faa5d22c064ac890e4f1a160d2999c6c4.json
├── indexes
│ └── helloworld
│ └── latest.json
├── layers
│ └── sha256
│ ├── 784e290aec5e97bf1e9ba17759fb0df3188a7285b08fccc84f882be4f2f65064
│ └── 989eddd15537fc00d20d560ae35c435b59b96c421412d75a85f22b7331a78aff
└── manifests
└── sha256
├── 656072e6e2bb60be3bd439460058c3240e29aa83e718e42fd213789d2bbfa0f0.json
└── 865cdfc985c9818b31b3b8094e405cd7e2d96fca4c19f07f38ef75a9077679d7.json
For containerd it results the following objects within the content store:
ctr content ls
DIGEST SIZE AGE LABELS
sha256:089d3e4f1c08951c5bc7b0a41ab9fca5445ac06dea642679d243db00a1948f0d 2.627kB 1 second containerd.io/distribution.source.index.docker.io=library/helloworld,containerd.io/gc.ref.content.l.0=sha256:989eddd15537fc00d20d560ae35c435b59b96c421412d75a85f22b7331a78aff,containerd.io/gc.ref.content.l.1=sha256:9530779d911fc36a50e156d36379d2e4d59eb259f28fba2311a80845a11988ec,containerd.io/gc.root=true,kraftkit.sh/oci.mediaType=application/vnd.oci.image.manifest.v1+json
sha256:784e290aec5e97bf1e9ba17759fb0df3188a7285b08fccc84f882be4f2f65064 217.1kB 1 second containerd.io/gc.root=true,kraftkit.sh/oci.mediaType=application/vnd.oci.image.layer.v1.tar
sha256:9530779d911fc36a50e156d36379d2e4d59eb259f28fba2311a80845a11988ec 1.96kB 1 second containerd.io/gc.root=true,kraftkit.sh/oci.mediaType=application/vnd.oci.image.config.v1+json
sha256:989eddd15537fc00d20d560ae35c435b59b96c421412d75a85f22b7331a78aff 241.7kB 1 second containerd.io/gc.root=true,kraftkit.sh/oci.mediaType=application/vnd.oci.image.layer.v1.tar
sha256:ce3ff4f9a957ab52f8187d03d8e45db4cbb35101ea4e65ff0f3f08b0ebbda111 4.773kB 1 second containerd.io/distribution.source.index.docker.io=library/helloworld,containerd.io/gc.ref.content.m.0=sha256:f63c483c81fd38dfc3c9088f7decaaec488cea3ff09648a5373ce6efb0c0234c,containerd.io/gc.ref.content.m.1=sha256:089d3e4f1c08951c5bc7b0a41ab9fca5445ac06dea642679d243db00a1948f0d,containerd.io/gc.root=true,kraftkit.sh/oci.mediaType=application/vnd.oci.image.index.v1+json
sha256:f63c483c81fd38dfc3c9088f7decaaec488cea3ff09648a5373ce6efb0c0234c 2.455kB 1 second containerd.io/distribution.source.index.docker.io=library/helloworld,containerd.io/gc.ref.content.l.0=sha256:784e290aec5e97bf1e9ba17759fb0df3188a7285b08fccc84f882be4f2f65064,containerd.io/gc.ref.content.l.1=sha256:fe5f6abe40068df5d5e98a08dc2f697faa5d22c064ac890e4f1a160d2999c6c4,containerd.io/gc.root=true,kraftkit.sh/oci.mediaType=application/vnd.oci.image.manifest.v1+json
sha256:fe5f6abe40068df5d5e98a08dc2f697faa5d22c064ac890e4f1a160d2999c6c4 1.788kB 1 second containerd.io/gc.root=true,kraftkit.sh/oci.mediaType=application/vnd.oci.image.config.v1+json