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OCI Registry As Storage
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OCI Registry As Storage

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Registries are evolving as Cloud Native Artifact Stores. To enable this goal, Microsoft has donated ORAS as means to enable various client libraries with a way to submit artifacts to OCI Spec Compliant registries. This repo is a staging ground for some yet to be determined upstream home.

As of Jan 24th, 2019, we're still evolving the library to incorporate annotation support. While we're initially testing ORAS with Helm 3 Registries and CNAB, we're very interested in feedback and contributions for other artifacts.

Want to reach the ORAS community and developers? Join us in the CNCF Slack #oras channel

More Background

For more background, please see:

Registries with known support

oras can push/pull any files to/from any registry with OCI image support of various mime types.

Getting Started

First, you must have access to a registry with OCI image support (see list above).

The simplest way to get started is to run the official Docker registry image locally:

docker run -it --rm -p 5000:5000 registry

This will start a Distribution server at localhost:5000 (with wide-open access and no persistence).

Next, install the oras CLI (see platform-specific installation instructions below).

Push a sample file to the registry:

cd /tmp && echo "hello world" > hi.txt
oras push localhost:5000/hello:latest hi.txt

Pull the file from the registry:

cd /tmp && rm -f hi.txt
oras pull localhost:5000/hello:latest
cat hi.txt  # should print "hello world"

Please see the Go Module section below for how this can be imported and used inside a Go project.


oras is a CLI that allows you to push and pull files from any registry with OCI image support.


Install oras using GoFish:

gofish install oras
==> Installing oras...
🐠  oras 0.7.0: installed in 65.131245ms

or install manually from the latest release artifacts:

# Linux
curl -LO

# macOS
curl -LO

# unpack, install, dispose
mkdir -p oras-install/
tar -zxf oras_0.7.0_*.tar.gz -C oras-install/
mv oras-install/oras /usr/local/bin/
rm -rf oras_0.7.0_*.tar.gz oras-install/

Then, to run:

oras help

Docker Image

A public Docker image containing the CLI is available on Docker Hub:

docker run -it --rm -v $(pwd):/workspace orasbot/oras:v0.7.0 help

Note: the default WORKDIR in the image is /workspace.


Run oras login in advance for any private registries. By default, this will store credentials in ~/.docker/config.json (same file as used by Docker). If you have authenticated to a registry previously using docker login, the credentials will be reused. Use the -c/--config option to specify an alternate location.

oras also accepts explicit credentials via options, for example,

oras pull -u username -p password

Example using with Docker registry

First, create a valid htpasswd file (must use -B for bcrypt):

htpasswd -cB -b auth.htpasswd myuser mypass

Next, start a registry using that file for auth:

docker run -it --rm -p 5000:5000 \
    -v $(pwd)/auth.htpasswd:/etc/docker/registry/auth.htpasswd \
    -e REGISTRY_AUTH="{htpasswd: {realm: localhost, path: /etc/docker/registry/auth.htpasswd}}" \

In a new window, login with oras:

oras login -u myuser -p mypass localhost:5000

You will notice a new entry for localhost:5000 appear in ~/.docker/config.json.

To remove the entry from the credentials file, use oras logout:

oras logout localhost:5000

Example using with insecure Docker registry

You want to login the registry without certificate if using the self-signed certificate or unencrypted HTTP connection Docker registry. oras support --insecure flag to login, it like the Docker daemon insecure-registries configuration.

First, create a valid htpasswd file (must use -B for bcrypt):

htpasswd -cB -b auth.htpasswd myuser mypass

Next, start a registry using that file for auth and listen the address:

docker run -it --rm -p 8443:443 \
    -v $(pwd)/auth.htpasswd:/etc/docker/registry/auth.htpasswd \
    -e REGISTRY_AUTH="{htpasswd: {realm: localhost, path: /etc/docker/registry/auth.htpasswd}}" \

In a new window, login with oras using the ip address not localhost:

oras login -u myuser -p mypass --insecure <registry-ip>:8443

You will notice a new entry for <registry-ip>:8443 appear in ~/.docker/config.json.

To remove the entry from the credentials file, use oras logout:

oras logout <registry-ip>:8443


Pushing single files to remote registry

oras push localhost:5000/hello:latest hi.txt

The default media type for all files is application/vnd.oci.image.layer.v1.tar.

The push a custom media type, use the format filename[:type]:

oras push localhost:5000/hello:latest hi.txt:application/

Pushing multiple files to remote registry

Just as docker images support multiple "layers", ORAS supports pushing multiple files. The file type is up to the implementer. You can push tar, yaml, text or whatever your artifact should be represented as.

To push multiple files with different media types:

oras push localhost:5000/hello:latest hi.txt:application/ bye.txt:application/

Pulling files from remote registry

oras pull localhost:5000/hello:latest

By default, only blobs with media type application/vnd.oci.image.layer.v1.tar will be downloaded.

To specify which media types to download, use the --media-type/-t flag:

oras pull localhost:5000/hello:latest -t application/

Or to allow all media types, use the --allow-all/-a flag:

oras pull localhost:5000/hello:latest -a

Go Module

The package can quickly be imported in other Go-based tools that wish to benefit from the ability to store arbitrary content in container registries.



package main

import (


	ocispec ""

func check(e error) {
	if e != nil {

func main() {
	ref := "localhost:5000/oras:test"
	fileName := "hello.txt"
	fileContent := []byte("Hello World!\n")
	customMediaType := ""

	ctx := context.Background()
	resolver := docker.NewResolver(docker.ResolverOptions{})

	// Push file(s) w custom mediatype to registry
	memoryStore := content.NewMemoryStore()
	desc := memoryStore.Add(fileName, customMediaType, fileContent)
	pushContents := []ocispec.Descriptor{desc}
	fmt.Printf("Pushing %s to %s...\n", fileName, ref)
	desc, err := oras.Push(ctx, resolver, ref, memoryStore, pushContents)
	fmt.Printf("Pushed to %s with digest %s\n", ref, desc.Digest)

	// Pull file(s) from registry and save to disk
	fmt.Printf("Pulling from %s and saving to %s...\n", ref, fileName)
	fileStore := content.NewFileStore("")
	defer fileStore.Close()
	allowedMediaTypes := []string{customMediaType}
	desc, _, err = oras.Pull(ctx, resolver, ref, fileStore, oras.WithAllowedMediaTypes(allowedMediaTypes))
	fmt.Printf("Pulled from %s with digest %s\n", ref, desc.Digest)
	fmt.Printf("Try running 'cat %s'\n", fileName)
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