Provided by: golang-github-containers-image_5.23.1-3_all 
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.
credential-helpers
An array of default credential helpers used as external credential stores. Note
that "containers-auth.json" is a reserved value to use auth files as specified in
containers-auth.json(5). The credential helpers are set to ["containers-
auth.json"] if none are specified.
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)
- [*.]host
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. It can also include wildcarded subdomains
in the format *.example.com. The wildcard should only be present at the beginning as
shown in the formats above. Other cases will not work. For example, *.example.com is valid
but example.*.com, *.example.com/foo and *.example.com:5000/foo/bar:baz are not. Note
that * matches an arbitrary number of subdomains. *.example.com will hence match
bar.example.com, foo.bar.example.com and so on.
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 Dockerfiles, 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.
With a prefix containing a wildcard in the format: "*.example.com" for subdomain matching,
the location can be empty. In such a case, prefix matching will occur, but no reference
rewrite will occur. The original requested image string will be used as-is. But other
settings like insecure / blocked / mirrors will be applied to matching images.
Example: Given
prefix = "*.example.com"
requests for the image blah.example.com/foo/myimage:latest will be used as-is. But other
settings like insecure/blocked/mirrors will be applied to matching images
mirror An array of TOML tables specifying (possibly-partial) mirrors for the prefix-rooted
namespace (i.e., the current [[registry]] TOML table).
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: - location： same
semantics as specified in the [[registry]] TOML table - insecure： same semantics as
specified in the [[registry]] TOML table - pull-from-mirror: all, digest-only or tag-only.
If "digest-only"， mirrors will only be used for digest pulls. Pulling images by tag can
potentially yield different images, depending on which endpoint we pull from. Restricting
mirrors to pulls by digest avoids that issue. If "tag-only", mirrors will only be used
for tag pulls. For a more up-to-date and expensive mirror that it is less likely to be
out of sync if tags move, it should not be unnecessarily used for digest references.
Default is "all" (or left empty), mirrors will be used for both digest pulls and tag pulls
unless the mirror-by-digest-only is set for the primary registry. Note that this per-
mirror setting is allowed only when mirror-by-digest-only is not configured for the
primary registry.
mirror-by-digest-only
true or false. If true, mirrors will only be used during pulling if the image
reference includes a digest. Note that if all mirrors are configured to be digest-
only, images referenced by a tag will only use the primary registry. If all
mirrors are configured to be tag-only, images referenced by a digest will only use
the primary registry.
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: Redirection and mirrors are currently processed only when reading images, not when
pushing to a registry; that may change in the future.
Short-Name Aliasing
The use of unqualified-search registries entails an ambiguity as it is unclear from which
registry a given image, referenced by a short name, may be pulled from.
As mentioned in the note at the end of this man page, using short names is subject to the
risk of hitting squatted registry namespaces. If the unqualified-search registries are
set to ["registry1.com", "registry2.com"] an attacker may take over a namespace of
registry1.com such that an image may be pulled from registry1.com instead of the intended
source registry2.com.
While it is highly recommended to always use fully-qualified image references, existing
deployments using short names may not be easily changed. To circumvent the aforementioned
ambiguity, so called short-name aliases can be configured that point to a fully-qualified
image reference.
Short-name aliases can be configured in the [aliases] table in the form of "name"="value"
with the left-hand name being the short name (e.g., "image") and the right-hand value
being the fully-qualified image reference (e.g., "registry.com/namespace/image"). Note
that neither "name" nor "value" can include a tag or digest. Moreover, "name" must be a
short name and hence cannot include a registry domain or refer to localhost.
When pulling a short name, the configured aliases table will be used for resolving the
short name. If a matching alias is found, it will be used without further consulting the
unqualified-search registries list. If no matching alias is found, the behavior can be
controlled via the short-name-mode option as described below.
Note that tags and digests are stripped off a user-specified short name for alias
resolution. Hence, "image", "image:tag" and "image@digest" all resolve to the same alias
(i.e., "image"). Stripped off tags and digests are later appended to the resolved alias.
Further note that drop-in configuration files (see containers-registries.conf.d(5)) can
override aliases in the specific loading order of the files. If the "value" of an alias
is empty (i.e., ""), the alias will be erased. However, a given "name" may only be
specified once in a single config file.
Short-Name Aliasing: Modes
The short-name-mode option supports three modes to control the behaviour of short-name
resolution.
• enforcing: If only one unqualified-search registry is set, use it as there is no
ambiguity. If there is more than one registry and the user program is running in
a terminal (i.e., stdout & stdin are a TTY), prompt the user to select one of the
specified search registries. If the program is not running in a terminal, the
ambiguity cannot be resolved which will lead to an error.
• permissive: Behaves as enforcing but does not lead to an error if the program is
not running in a terminal. Instead, fallback to using all unqualified-search
registries.
• disabled: Use all unqualified-search registries without prompting.
If short-name-mode is not specified at all or left empty, default to the permissive mode.
If the user-specified short name was not aliased already, the enforcing and permissive
mode if prompted, will record a new alias after a successful pull. Note that the recorded
alias will be written to /var/cache/containers/short-name-aliases.conf for root to have a
clear separation between possibly human-edited registries.conf files and the machine-
generated short-name-aliases-conf. Note that $HOME/.cache is used for rootless users. If
an alias is specified in a registries.conf file and also the machine-generated short-name-
aliases.conf, the short-name-aliases.conf file has precedence.
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
[[registry]]
location = "registry.com"
[[registry.mirror]]
location = "mirror.registry.com"
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.
Note that a mirror is associated only with the current [[registry]] TOML table. If using
the example above, pulling the image registry.com/image:latest will hence only reach out
to mirror.registry.com, and the mirrors associated with example.com/foo will not be
considered.
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-auth.json(5) containers-certs.d(5)
HISTORY
Dec 2019, Warning added for unqualified image names by Tom Sweeney tsweeney@redhat.com
⟨mailto:tsweeney@redhat.com⟩
Mar 2019, Added additional configuration format by Sascha Grunert sgrunert@suse.com
⟨mailto:sgrunert@suse.com⟩
Aug 2018, Renamed to containers-registries.conf(5) by Valentin Rothberg vrothberg@suse.com
⟨mailto:vrothberg@suse.com⟩
Jun 2018, Updated by Tom Sweeney tsweeney@redhat.com ⟨mailto:tsweeney@redhat.com⟩
Aug 2017, Originally compiled by Brent Baude bbaude@redhat.com ⟨mailto:bbaude@redhat.com⟩