% CONTAINERS-REGISTRIES.CONF(5) System-wide registry configuration file

% Brent Baude

% Aug 2017

# NAME

containers-registries.conf - Syntax of System Registry Configuration File

# DESCRIPTION

The CONTAINERS-REGISTRIES configuration file is a system-wide configuration

file for container image registries. The file format is TOML.

Container engines will use the `$HOME/.config/containers/registries.conf` if it exists, otherwise they will use `/etc/containers/registries.conf`

### GLOBAL SETTINGS

`unqualified-search-registries`

: An array of _host_[`:`_port_] registries to try when pulling an unqualified image, in order.

### NAMESPACED `[[registry]]` SETTINGS

The bulk of the configuration is represented as an array of `[[registry]]`

TOML tables; the settings may therefore differ among different registries

as well as among different namespaces/repositories within a registry.

#### Choosing a `[[registry]]` TOML table

Given an image name, a single `[[registry]]` TOML table is chosen based on its `prefix` field.

`prefix`

: A prefix of the user-specified image name, i.e. using one of the following formats:

    - _host_[`:`_port_]

    - _host_[`:`_port_]`/`_namespace_[`/`_namespace_…]

    - _host_[`:`_port_]`/`_namespace_[`/`_namespace_…]`/`_repo_

    - _host_[`:`_port_]`/`_namespace_[`/`_namespace_…]`/`_repo_(`:`_tag|`@`_digest_)

    The user-specified image name must start with the specified `prefix` (and continue

    with the appropriate separator) for a particular `[[registry]]` TOML table to be

    considered; (only) the TOML table with the longest match is used.

    As a special case, the `prefix` field can be missing; if so, it defaults to the value

    of the `location` field (described below).

#### Per-namespace settings

`insecure`

: `true` or `false`.

    By default, container runtimes require TLS when retrieving images from a registry.

    If `insecure` is set to `true`, unencrypted HTTP as well as TLS connections with untrusted

    certificates are allowed.

`blocked`

: `true` or `false`.

    If `true`, pulling images with matching names is forbidden.

#### Remapping and mirroring registries

The user-specified image reference is, primarily, a "logical" image name, always used for naming

the image.  By default, the image reference also directly specifies the registry and repository

to use, but the following options can be used to redirect the underlying accesses

to different registry servers or locations (e.g. to support configurations with no access to the

internet without having to change `Dockerfile`s, or to add redundancy).

`location`

: Accepts the same format as the `prefix` field, and specifies the physical location

    of the `prefix`-rooted namespace.

    By default, this equal to `prefix` (in which case `prefix` can be omitted and the

    `[[registry]]` TOML table can only specify `location`).

    Example: Given

    ```

    prefix = "example.com/foo"

    location = "internal-registry-for-example.net/bar"

    ```

    requests for the image `example.com/foo/myimage:latest` will actually work with the

    `internal-registry-for-example.net/bar/myimage:latest` image.

`mirror`

: An array of TOML tables specifying (possibly-partial) mirrors for the

    `prefix`-rooted namespace.

    The mirrors are attempted in the specified order; the first one that can be

    contacted and contains the image will be used (and if none of the mirrors contains the image,

    the primary location specified by the `registry.location` field, or using the unmodified

    user-specified reference, is tried last).

    Each TOML table in the `mirror` array can contain the following fields, with the same semantics

    as if specified in the `[[registry]]` TOML table directly:

    - `location`

    - `insecure`

`mirror-by-digest-only`

: `true` or `false`.

    If `true`, mirrors will only be used during pulling if the image reference includes a digest.

    Referencing an image by digest ensures that the same is always used

    (whereas referencing an image by a tag may cause different registries to return

    different images if the tag mapping is out of sync).

    Note that if this is `true`, images referenced by a tag will only use the primary

    registry, failing if that registry is not accessible.

*Note*: Redirection and mirrors are currently processed only when reading images, not when pushing

to a registry; that may change in the future.

#### Normalization of docker.io references

The Docker Hub `docker.io` is handled in a special way: every push and pull

operation gets internally normalized with `/library` if no other specific

namespace is defined (for example on `docker.io/namespace/image`).

(Note that the above-described normalization happens to match the behavior of

Docker.)

This means that a pull of `docker.io/alpine` will be internally translated to

`docker.io/library/alpine`. A pull of `docker.io/user/alpine` will not be

rewritten because this is already the correct remote path.

Therefore, to remap or mirror the `docker.io` images in the (implied) `/library`

namespace (or that whole namespace), the prefix and location fields in this

configuration file must explicitly include that `/library` namespace. For

example `prefix = "docker.io/library/alpine"` and not `prefix =

"docker.io/alpine"`. The latter would match the `docker.io/alpine/*`

repositories but not the `docker.io/[library/]alpine` image).

### EXAMPLE

```

unqualified-search-registries = ["example.com"]

[[registry]]

prefix = "example.com/foo"

insecure = false

blocked = false

location = "internal-registry-for-example.com/bar"

[[registry.mirror]]

location = "example-mirror-0.local/mirror-for-foo"

[[registry.mirror]]

location = "example-mirror-1.local/mirrors/foo"

insecure = true

```

Given the above, a pull of `example.com/foo/image:latest` will try:

    1. `example-mirror-0.local/mirror-for-foo/image:latest`

    2. `example-mirror-1.local/mirrors/foo/image:latest`

    3. `internal-registry-for-example.net/bar/image:latest`

in order, and use the first one that exists.

## VERSION 1 FORMAT - DEPRECATED

VERSION 1 format is still supported but it does not support

using registry mirrors, longest-prefix matches, or location rewriting.

The TOML format is used to build a simple list of registries under three

categories: `registries.search`, `registries.insecure`, and `registries.block`.

You can list multiple registries using a comma separated list.

Search registries are used when the caller of a container runtime does not fully specify the

container image that they want to execute.  These registries are prepended onto the front

of the specified container image until the named image is found at a registry.

Note that insecure registries can be used for any registry, not just the registries listed

under search.

The `registries.insecure` and `registries.block` lists have the same meaning as the

`insecure` and `blocked` fields in the current version.

### EXAMPLE

The following example configuration defines two searchable registries, one

insecure registry, and two blocked registries.

```

[registries.search]

registries = ['registry1.com', 'registry2.com']

[registries.insecure]

registries = ['registry3.com']

[registries.block]

registries = ['registry.untrusted.com', 'registry.unsafe.com']

```

# NOTE: RISK OF USING UNQUALIFIED IMAGE NAMES

We recommend always using fully qualified image names including the registry

server (full dns name), namespace, image name, and tag

(e.g., registry.redhat.io/ubi8/ubi:latest). When using short names, there is

always an inherent risk that the image being pulled could be spoofed. For

example, a user wants to pull an image named `foobar` from a registry and

expects it to come from myregistry.com. If myregistry.com is not first in the

search list, an attacker could place a different `foobar` image at a registry

earlier in the search list. The user would accidentally pull and run the

attacker's image and code rather than the intended content. We recommend only

adding registries which are completely trusted, i.e. registries which don't

allow unknown or anonymous users to create accounts with arbitrary names. This

will prevent an image from being spoofed, squatted or otherwise made insecure.

If it is necessary to use one of these registries, it should be added at the

end of the list.

It is recommended to use fully-qualified images for pulling as

the destination registry is unambiguous. Pulling by digest

(i.e., quay.io/repository/name@digest) further eliminates the ambiguity of

tags.

# SEE ALSO

  containers-certs.d(5)

# HISTORY

Dec 2019, Warning added for unqualified image names by Tom Sweeney <tsweeney@redhat.com>

Mar 2019, Added additional configuration format by Sascha Grunert <sgrunert@suse.com>

Aug 2018, Renamed to containers-registries.conf(5) by Valentin Rothberg <vrothberg@suse.com>

Jun 2018, Updated by Tom Sweeney <tsweeney@redhat.com>

Aug 2017, Originally compiled by Brent Baude <bbaude@redhat.com>