containers-common/containers-auth.json.5.md

% containers-auth.json 5

NAME

containers-auth.json - syntax for the registry authentication file

DESCRIPTION

A file in JSON format controlling authentication against container image registries. The primary (read/write) file is stored at ${XDG_RUNTIME_DIR}/containers/auth.json on Linux; on Windows and macOS, at $HOME/.config/containers/auth.json.

When searching for the credential for a registry, the following files will be read in sequence until the valid credential is found: first reading the primary (read/write) file, or the explicit override using an option of the calling application. If credentials are not present there, the search continues in ${XDG_CONFIG_HOME}/containers/auth.json (usually ~/.config/containers/auth.json), $HOME/.docker/config.json, $HOME/.dockercfg.

Except for the primary (read/write) file, other files are read-only unless the user, using an option of the calling application, explicitly points at it as an override.

FORMAT

The auth.json file stores, or references, credentials that allow the user to authenticate to container image registries. It is primarily managed by a login command from a container tool such as podman login, buildah login, or skopeo login.

Each entry contains a single hostname (e.g., docker.io) or a namespace (e.g., quay.io/user/image) as a key, and credentials in the form of a base64-encoded string as value of auth. The base64-encoded string contains a concatenation of the username, a colon, and the password.

When checking for available credentials, the relevant repository is matched against available keys in its hierarchical order, going from most-specific to least-specific. For example, an image pull for my-registry.local/namespace/user/image:latest will result in a lookup in auth.json in the following order:

• my-registry.local/namespace/user/image
• my-registry.local/namespace/user
• my-registry.local/namespace
• my-registry.local

This way it is possible to setup multiple credentials for a single registry which can be distinguished by their path.

The following example shows the values found in auth.json after the user logged in to their accounts on quay.io and docker.io:

{
	"auths": {
		"docker.io": {
			"auth": "erfi7sYi89234xJUqaqxgmzcnQ2rRFWM5aJX0EC="
		},
		"quay.io": {
			"auth": "juQAqGmz5eR1ipzx8Evn6KGdw8fEa1w5MWczmgY="
		}
	}
}

This example demonstrates how to use multiple paths for a single registry, while preserving a fallback for my-registry.local:

{
	"auths": {
		"my-registry.local/foo/bar/image": {
			"auth": "…"
		},
		"my-registry.local/foo": {
			"auth": "…"
		},
		"my-registry.local": {
			"auth": "…"
		},
	}
}

An entry can be removed by using a logout command from a container tool such as podman logout or buildah logout.

In addition, credential helpers can be configured for specific registries, and the credentials-helper software can be used to manage the credentials more securely than storing only base64-encoded credentials in auth.json.

When the credential helper is in use on a Linux platform, the auth.json file would contain keys that specify the registry domain, and values that specify the suffix of the program to use (i.e. everything after docker-credential-). For example:

{
    "auths": {
        "localhost:5001": {}
    },
    "credHelpers": {
		"registry.example.com": "secretservice"
	}
}

For more information on credential helpers, please reference the GitHub docker-credential-helpers project.

SEE ALSO

buildah-login(1), buildah-logout(1), podman-login(1), podman-logout(1), skopeo-login(1), skopeo-logout(1)

HISTORY

Feb 2020, Originally compiled by Tom Sweeney tsweeney@redhat.com