All users can access container images stored in centralized repositories called OCI registries. Pushing OCI artifacts to the registries is the first step in distributing them. These artifacts can be pulled by other people and used in their own environment once they have been stored.

Pushing

Pushing artifacts with single file

Pushing a single file artifact involves referencing the unique artifact type and a file. Defining an Artifact uses the config.mediaType as the unique artifact type. If a config object is provided, the mediaType extension defines the config filetype. If a null config is passed, the config extension must be removed.

See: Defining a Unique Artifact Type

The following sample defines a new Artifact Type of Acme Rocket, using application/vnd.acme.rocket.config as the manifest.config.mediaType.

• Create a sample file to push/pull as an artifact

  echo "hello world" > artifact.txt

• Push the sample file to the registry:

  oras push localhost:5000/hello-artifact:v1 \
  --artifact-type application/vnd.acme.rocket.config \
  ./artifact.txt

• Pull the file from the registry:

  rm -f artifact.txt # first delete the file
  oras pull localhost:5000/hello-artifact:v1
  cat artifact.txt  # should print "hello world"

• Push the sample file, with a layer mediaType, using the format filename[:type]:

  oras push localhost:5000/hello-artifact:v2 \
  --artifact-type application/vnd.acme.rocket.config \
    artifact.txt:text/plain

Pushing artifacts with config files

The OCI distribution-spec provides for storing optional config objects. These can be used by the artifact to determine how or where to process and/or route the blobs. When providing a config object, the version and file type is required.

• Create a config file

  echo "{\"name\":\"foo\",\"value\":\"bar\"}" > config.json

• Push an artifact, with the config.json file

  oras push localhost:5000/hello-artifact:v2 \
  --config config.json:application/vnd.acme.rocket.config.v1+json \
    artifact.txt:text/plain

Pushing artifacts with multiple files

Just as container images support multiple "layers" represented as blobs, ORAS supports pushing multiple layers. The layer type is up to the artifact author. You may push .tar representing a collection of files, individual files like .yaml, .txt or whatever your artifact should be represented as. Each layer type should have a mediaType representing the type of blob content. In this example, we'll push a collection of files.

• A single file (artifact.txt) that represents overview content that might be displayed as a repository overview
• A collection of files (docs/*) that represents detailed content. When specifying a directory, ORAS will automatically tar the contents.

See OCI Artifacts for more details.

• Create additional blobs

  mkdir docs
  echo "Docs on this artifact" > ./docs/readme.md
  echo "More content for this artifact" > ./docs/readme2.md

• Create a config file, referencing the entry doc file

  echo "{\"doc\":\"readme.md\"}" > config.json

• Push multiple files with different mediaTypes:

  oras push localhost:5000/hello-artifact:v2 \
    --config config.json:application/vnd.acme.rocket.config.v1+json \
    artifact.txt:text/plain \
    ./docs/:application/vnd.acme.rocket.docs.layer.v1+tar

• The push will generate a manifest. Run the following command to output the manifest:

  oras manifest fetch localhost:5000/hello-artifact:v2 --pretty

  Results in:

  {
    "schemaVersion": 2,
    "config": {
      "mediaType": "application/vnd.acme.rocket.config.v1+json",
      "digest": "sha256:7aa5d0dee9a3a73c81db4356cf7aa5666e175d96e68ee763eeb977bd7ba59ee5",
      "size": 20
    },
    "layers": [
      {
        "mediaType": "text/plain",
        "digest": "sha256:a948904f2f0f479b8f8197694b30184b0d2ed1c1cd2a1ec0fb85d299a192a447",
        "size": 12,
        "annotations": {
          "org.opencontainers.image.title": "artifact.txt"
        }
      },
      {
        "mediaType": "application/vnd.acme.rocket.docs.layer.v1+tar",
        "digest": "sha256:20ae7d51e2365405e6942439140d897548e1d4610db60354aef8a5ce1f1699a7",
        "size": 196,
        "annotations": {
          "io.deis.oras.content.digest": "sha256:4329ea6c620ca4e9cedc5f5e8040432114cb5d64fc53107ea870db149e3d2b9e",
          "io.deis.oras.content.unpack": "true",
          "org.opencontainers.image.title": "docs"
        }
      }
    ]
  }

Pulling

Pulling artifacts involves specifying the content addressable artifact, along with the type of artifact.

oras pull localhost:5000/hello-artifact:v2

Using cache when pulling artifacts

ORAS pulls the artifact into a content-addressable storage (CAS) cache if the content is not available locally to save bandwidth and disk I/O. Once the content is availabe in the cache, ORAS copies the artifact to the desired location. The cache directory is specified by using the environment variable ORAS_CACHE. If not specified, cache is not used.

# Set cache root
export ORAS_CACHE=~/.oras/cache

# Pull artifacts as usual
oras pull localhost:5000/hello:latest