1CONTAINERS-REGISTRIES.CONF(5) configuration CONTAINERS-REGISTRIES.CONF(5)
2Brent Baude Aug 2017
6
9 containers-registries.conf - Syntax of System Registry Configuration
10 File
11
15 The CONTAINERS-REGISTRIES configuration file is a system-wide configu‐
16 ration file for container image registries. The file format is TOML.
17 Container engines will use the $HOME/.config/containers/registries.conf
20 if it exists, otherwise they will use /etc/containers/registries.conf
21 GLOBAL SETTINGS
24 unqualified-search-registries
25 An array of host[:port] registries to try when pulling an un‐
26 qualified image, in order.
27 credential-helpers
30 An array of default credential helpers used as external creden‐
31 tial stores. Note that "containers-auth.json" is a reserved
32 value to use auth files as specified in containers-auth.json(5).
33 The credential helpers are set to ["containers-auth.json"] if
34 none are specified.
35 NAMESPACED [[registry]] SETTINGS
38 The bulk of the configuration is represented as an array of [[reg‐
39 istry]] TOML tables; the settings may therefore differ among different
40 registries as well as among different namespaces/repositories within a
41 registry.
42 Choosing a [[registry]] TOML table
45 Given an image name, a single [[registry]] TOML table is chosen based
46 on its prefix field.
47 prefix: A prefix of the user-specified image name, i.e. using one of
50 the following formats:
51 - host[:port]
52 - host[:port]/namespace[/_namespace_…]
53 - host[:port]/namespace[/_namespace_…]/repo
54 - host[:port]/namespace[/_namespace_…]/repo(:_tag|@digest)
55 - [*.]host
56 The user-specified image name must start with the specified prefix (and
59 continue with the appropriate separator) for a particular [[registry]]
60 TOML table to be considered; (only) the TOML table with the longest
61 match is used. It can also include wildcarded subdomains in the format
62 *.example.com. The wildcard should only be present at the beginning as
63 shown in the formats above. Other cases will not work. For example,
64 *.example.com is valid but example.*.com, *.example.com/foo and *.exam‐
65 ple.com:5000/foo/bar:baz are not. Note that * matches an arbitary num‐
66 ber of subdomains. *.example.com will hence match bar.example.com,
67 foo.bar.example.com and so on.
68 As a special case, the prefix field can be missing; if so, it defaults
71 to the value of the location field (described below).
72 Per-namespace settings
75 insecure
76 true or false. By default, container runtimes require TLS when
77 retrieving images from a registry. If insecure is set to true,
78 unencrypted HTTP as well as TLS connections with untrusted cer‐
79 tificates are allowed.
80 blocked
83 true or false. If true, pulling images with matching names is
84 forbidden.
85 Remapping and mirroring registries
88 The user-specified image reference is, primarily, a "logical" image
89 name, always used for naming the image. By default, the image refer‐
90 ence also directly specifies the registry and repository to use, but
91 the following options can be used to redirect the underlying accesses
92 to different registry servers or locations (e.g. to support configura‐
93 tions with no access to the internet without having to change Docker‐
94 files, or to add redundancy).
95 location
98 Accepts the same format as the prefix field, and specifies the
99 physical location of the prefix-rooted namespace.
100 By default, this equal to prefix (in which case prefix can be omitted
103 and the [[registry]] TOML table can only specify location).
104 Example: Given
107 prefix = "example.com/foo"
110 location = "internal-registry-for-example.net/bar"
111 requests for the image example.com/foo/myimage:latest will actually
115 work with the internal-registry-for-example.net/bar/myimage:latest im‐
116 age.
117 With a prefix containing a wildcard in the format: "*.example.com" for
120 subdomain matching, the location can be empty. In such a case, prefix
121 matching will occur, but no reference rewrite will occur. The original
122 requested image string will be used as-is. But other settings like in‐
123 secure / blocked / mirrors will be applied to matching images.
124 Example: Given
127 prefix = "*.example.com"
130 requests for the image blah.example.com/foo/myimage:latest will be used
134 as-is. But other settings like insecure/blocked/mirrors will be applied
135 to matching images
136 mirror An array of TOML tables specifying (possibly-partial) mirrors
139 for the prefix-rooted namespace.
140 The mirrors are attempted in the specified order; the first one that
143 can be contacted and contains the image will be used (and if none of
144 the mirrors contains the image, the primary location specified by the
145 registry.location field, or using the unmodified user-specified refer‐
146 ence, is tried last).
147 Each TOML table in the mirror array can contain the following fields: -
150 location： same semantics as specified in the [[registry]] TOML table -
151 insecure： same semantics as specified in the [[registry]] TOML table -
152 pull-from-mirror: all, digest-only or tag-only. If "digest-only"，
153 mirrors will only be used for digest pulls. Pulling images by tag can
154 potentially yield different images, depending on which endpoint we pull
155 from. Restricting mirrors to pulls by digest avoids that issue. If
156 "tag-only", mirrors will only be used for tag pulls. For a more up-to-
157 date and expensive mirror that it is less likely to be out of sync if
158 tags move, it should not be unnecessarily used for digest references.
159 Default is "all" (or left empty), mirrors will be used for both digest
160 pulls and tag pulls unless the mirror-by-digest-only is set for the
161 primary registry. Note that this per-mirror setting is allowed only
162 when mirror-by-digest-only is not configured for the primary registry.
163 mirror-by-digest-only
166 true or false. If true, mirrors will only be used during
167 pulling if the image reference includes a digest. Note that if
168 all mirrors are configured to be digest-only, images referenced
169 by a tag will only use the primary registry. If all mirrors are
170 configured to be tag-only, images referenced by a digest will
171 only use the primary registry.
172 Referencing an image by digest ensures that the same is always used
175 (whereas referencing an image by a tag may cause different registries
176 to return different images if the tag mapping is out of sync).
177 Note: Redirection and mirrors are currently processed only when reading
180 images, not when pushing to a registry; that may change in the future.
181 Short-Name Aliasing
184 The use of unqualified-search registries entails an ambiguity as it is
185 unclear from which registry a given image, referenced by a short name,
186 may be pulled from.
187 As mentioned in the note at the end of this man page, using short names
190 is subject to the risk of hitting squatted registry namespaces. If the
191 unqualified-search registries are set to ["registry1.com", "reg‐
192 istry2.com"] an attacker may take over a namespace of registry1.com
193 such that an image may be pulled from registry1.com instead of the in‐
194 tended source registry2.com.
195 While it is highly recommended to always use fully-qualified image ref‐
198 erences, existing deployments using short names may not be easily
199 changed. To circumvent the aforementioned ambiguity, so called short-
200 name aliases can be configured that point to a fully-qualified image
201 reference.
202 Short-name aliases can be configured in the [aliases] table in the form
205 of "name"="value" with the left-hand name being the short name (e.g.,
206 "image") and the right-hand value being the fully-qualified image ref‐
207 erence (e.g., "registry.com/namespace/image"). Note that neither
208 "name" nor "value" can include a tag or digest. Moreover, "name" must
209 be a short name and hence cannot include a registry domain or refer to
210 localhost.
211 When pulling a short name, the configured aliases table will be used
214 for resolving the short name. If a matching alias is found, it will be
215 used without further consulting the unqualified-search registries list.
216 If no matching alias is found, the behavior can be controlled via the
217 short-name-mode option as described below.
218 Note that tags and digests are stripped off a user-specified short name
221 for alias resolution. Hence, "image", "image:tag" and "image@digest"
222 all resolve to the same alias (i.e., "image"). Stripped off tags and
223 digests are later appended to the resolved alias.
224 Further note that drop-in configuration files (see containers-reg‐
227 istries.conf.d(5)) can override aliases in the specific loading order
228 of the files. If the "value" of an alias is empty (i.e., ""), the
229 alias will be erased. However, a given "name" may only be specified
230 once in a single config file.
231 Short-Name Aliasing: Modes
234 The short-name-mode option supports three modes to control the behav‐
235 iour of short-name resolution.
236 • enforcing: If only one unqualified-search registry is set, use
239 it as there is no ambiguity. If there is more than one reg‐
240 istry and the user program is running in a terminal (i.e.,
241 stdout & stdin are a TTY), prompt the user to select one of
242 the specified search registries. If the program is not run‐
243 ning in a terminal, the ambiguity cannot be resolved which
244 will lead to an error.
245 • permissive: Behaves as enforcing but does not lead to an error
247 if the program is not running in a terminal. Instead, fall‐
248 back to using all unqualified-search registries.
249 • disabled: Use all unqualified-search registries without
251 prompting.
252 If short-name-mode is not specified at all or left empty, default to
256 the permissive mode. If the user-specified short name was not aliased
257 already, the enforcing and permissive mode if prompted, will record a
258 new alias after a successful pull. Note that the recorded alias will
259 be written to /var/cache/containers/short-name-aliases.conf for root to
260 have a clear separation between possibly human-edited registries.conf
261 files and the machine-generated short-name-aliases-conf. Note that
262 $HOME/.cache is used for rootless users. If an alias is specified in a
263 registries.conf file and also the machine-generated short-name-
264 aliases.conf, the short-name-aliases.conf file has precedence.
265 Normalization of docker.io references
268 The Docker Hub docker.io is handled in a special way: every push and
269 pull operation gets internally normalized with /library if no other
270 specific namespace is defined (for example on docker.io/namespace/im‐
271 age).
272 (Note that the above-described normalization happens to match the be‐
275 havior of Docker.)
276 This means that a pull of docker.io/alpine will be internally trans‐
279 lated to docker.io/library/alpine. A pull of docker.io/user/alpine will
280 not be rewritten because this is already the correct remote path.
281 Therefore, to remap or mirror the docker.io images in the (implied)
284 /library namespace (or that whole namespace), the prefix and location
285 fields in this configuration file must explicitly include that /library
286 namespace. For example prefix = "docker.io/library/alpine" and not pre‐
287 fix = "docker.io/alpine". The latter would match the docker.io/alpine/*
288 repositories but not the docker.io/[library/]alpine image).
289 EXAMPLE
292 unqualified-search-registries = ["example.com"]
293 [[registry]]
295 prefix = "example.com/foo"
296 insecure = false
297 blocked = false
298 location = "internal-registry-for-example.com/bar"
299 [[registry.mirror]]
301 location = "example-mirror-0.local/mirror-for-foo"
302 [[registry.mirror]]
304 location = "example-mirror-1.local/mirrors/foo"
305 insecure = true
306 Given the above, a pull of example.com/foo/image:latest will try:
310 1. example-mirror-0.local/mirror-for-foo/image:latest
311 2. example-mirror-1.local/mirrors/foo/image:latest
312 3. internal-registry-for-example.net/bar/image:latest
313 in order, and use the first one that exists.
316
319 VERSION 1 format is still supported but it does not support using reg‐
320 istry mirrors, longest-prefix matches, or location rewriting.
321 The TOML format is used to build a simple list of registries under
324 three categories: registries.search, registries.insecure, and reg‐
325 istries.block. You can list multiple registries using a comma sepa‐
326 rated list.
327 Search registries are used when the caller of a container runtime does
330 not fully specify the container image that they want to execute. These
331 registries are prepended onto the front of the specified container im‐
332 age until the named image is found at a registry.
333 Note that insecure registries can be used for any registry, not just
336 the registries listed under search.
337 The registries.insecure and registries.block lists have the same mean‐
340 ing as the insecure and blocked fields in the current version.
341 EXAMPLE
344 The following example configuration defines two searchable registries,
345 one insecure registry, and two blocked registries.
346 [registries.search]
349 registries = ['registry1.com', 'registry2.com']
350 [registries.insecure]
352 registries = ['registry3.com']
353 [registries.block]
355 registries = ['registry.untrusted.com', 'registry.unsafe.com']
356
361 We recommend always using fully qualified image names including the
362 registry server (full dns name), namespace, image name, and tag (e.g.,
363 registry.redhat.io/ubi8/ubi:latest). When using short names, there is
364 always an inherent risk that the image being pulled could be spoofed.
365 For example, a user wants to pull an image named foobar from a registry
366 and expects it to come from myregistry.com. If myregistry.com is not
367 first in the search list, an attacker could place a different foobar
368 image at a registry earlier in the search list. The user would acciden‐
369 tally pull and run the attacker's image and code rather than the in‐
370 tended content. We recommend only adding registries which are com‐
371 pletely trusted, i.e. registries which don't allow unknown or anonymous
372 users to create accounts with arbitrary names. This will prevent an im‐
373 age from being spoofed, squatted or otherwise made insecure. If it is
374 necessary to use one of these registries, it should be added at the end
375 of the list.
376 It is recommended to use fully-qualified images for pulling as the des‐
379 tination registry is unambiguous. Pulling by digest (i.e.,
380 quay.io/repository/name@digest) further eliminates the ambiguity of
381 tags.
382
386 containers-auth.json(5) containers-certs.d(5)
387
391 Dec 2019, Warning added for unqualified image names by Tom Sweeney
392 tsweeney@redhat.com ⟨mailto:tsweeney@redhat.com⟩
393 Mar 2019, Added additional configuration format by Sascha Grunert
396 sgrunert@suse.com ⟨mailto:sgrunert@suse.com⟩
397 Aug 2018, Renamed to containers-registries.conf(5) by Valentin Rothberg
400 vrothberg@suse.com ⟨mailto:vrothberg@suse.com⟩
401 Jun 2018, Updated by Tom Sweeney tsweeney@redhat.com
404 ⟨mailto:tsweeney@redhat.com⟩
405 Aug 2017, Originally compiled by Brent Baude bbaude@redhat.com
408 ⟨mailto:bbaude@redhat.com⟩
409registry System-wide CONTAINERS-REGISTRIES.CONF(5)