# Docker Registry HTTP API V2 ## Introduction The _Docker Registry HTTP API_ is the protocol to facilitate distribution of images to the docker engine. It interacts with instances of the docker registry, which is a service to manage information about docker images and enable their distribution. The specification covers the operation of version 2 of this API, known as _Docker Registry HTTP API V2_. While the V1 registry protocol is usable, there are several problems with the architecture that have led to this new version. The main driver of this specification is a set of changes to the docker the image format, covered in [docker/docker#8093](https://github.com/docker/docker/issues/8093). The new, self-contained image manifest simplifies image definition and improves security. This specification will build on that work, leveraging new properties of the manifest format to improve performance, reduce bandwidth usage and decrease the likelihood of backend corruption. For relevant details and history leading up to this specification, please see the following issues: - [docker/docker#8093](https://github.com/docker/docker/issues/8093) - [docker/docker#9015](https://github.com/docker/docker/issues/9015) - [docker/docker-registry#612](https://github.com/docker/docker-registry/issues/612) ### Scope This specification covers the URL layout and protocols of the interaction between docker registry and docker core. This will affect the docker core registry API and the rewrite of docker-registry. Docker registry implementations may implement other API endpoints, but they are not covered by this specification. This includes the following features: - Namespace-oriented URI Layout - PUSH/PULL registry server for V2 image manifest format - Resumable layer PUSH support - V2 Client library implementation While authentication and authorization support will influence this specification, details of the protocol will be left to a future specification. Relevant header definitions and error codes are present to provide an indication of what a client may encounter. #### Future There are features that have been discussed during the process of cutting this specification. The following is an incomplete list: - Immutable image references - Multiple architecture support - Migration from v2compatibility representation These may represent features that are either out of the scope of this specification, the purview of another specification or have been deferred to a future version. ### Use Cases For the most part, the use cases of the former registry API apply to the new version. Differentiating use cases are covered below. #### Image Verification A docker engine instance would like to run verified image named "library/ubuntu", with the tag "latest". The engine contacts the registry, requesting the manifest for "library/ubuntu:latest". An untrusted registry returns a manifest. Before proceeding to download the individual layers, the engine verifies the manifest's signature, ensuring that the content was produced from a trusted source and no tampering has occurred. After each layer is downloaded, the engine verifies the digest of the layer, ensuring that the content matches that specified by the manifest. #### Resumable Push Company X's build servers lose connectivity to docker registry before completing an image layer transfer. After connectivity returns, the build server attempts to re-upload the image. The registry notifies the build server that the upload has already been partially attempted. The build server responds by only sending the remaining data to complete the image file. #### Resumable Pull Company X is having more connectivity problems but this time in their deployment datacenter. When downloading an image, the connection is interrupted before completion. The client keeps the partial data and uses http `Range` requests to avoid downloading repeated data. #### Layer Upload De-duplication Company Y's build system creates two identical docker layers from build processes A and B. Build process A completes uploading the layer before B. When process B attempts to upload the layer, the registry indicates that its not necessary because the layer is already known. If process A and B upload the same layer at the same time, both operations will proceed and the first to complete will be stored in the registry (Note: we may modify this to prevent dogpile with some locking mechanism). ### Changes The V2 specification has been written to work as a living document, specifying only what is certain and leaving what is not specified open or to future changes. Only non-conflicting additions should be made to the API and accepted changes should avoid preventing future changes from happening. This section should be updated when changes are made to the specification, indicating what is different. Optionally, we may start marking parts of the specification to correspond with the versions enumerated here. Each set of changes is given a letter corresponding to a set of modifications that were applied to the baseline specification. These are merely for reference and shouldn't be used outside the specification other than to identify a set of modifications.
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## Overview This section covers client flows and details of the API endpoints. The URI layout of the new API is structured to support a rich authentication and authorization model by leveraging namespaces. All endpoints will be prefixed by the API version and the repository name: /v2// For example, an API endpoint that will work with the `library/ubuntu` repository, the URI prefix will be: /v2/library/ubuntu/ This scheme provides rich access control over various operations and methods using the URI prefix and http methods that can be controlled in variety of ways. Classically, repository names have always been two path components where each path component is less than 30 characters. The V2 registry API does not enforce this. The rules for a repository name are as follows: 1. A repository name is broken up into _path components_. A component of a repository name must be at least one lowercase, alpha-numeric characters, optionally separated by periods, dashes or underscores. More strictly, it must match the regular expression `[a-z0-9]+(?:[._-][a-z0-9]+)*`. 2. If a repository name has two or more path components, they must be separated by a forward slash ("/"). 3. The total length of a repository name, including slashes, must be less the 256 characters. These name requirements _only_ apply to the registry API and should accept a superset of what is supported by other docker ecosystem components. All endpoints should support aggressive http caching, compression and range headers, where appropriate. The new API attempts to leverage HTTP semantics where possible but may break from standards to implement targeted features. For detail on individual endpoints, please see the [_Detail_](#detail) section. ### Errors Actionable failure conditions, covered in detail in their relevant sections, are reported as part of 4xx responses, in a json response body. One or more errors will be returned in the following format: { "errors:" [{ "code": , "message": , "detail": }, ... ] } The `code` field will be a unique identifier, all caps with underscores by convention. The `message` field will be a human readable string. The optional `detail` field may contain arbitrary json data providing information the client can use to resolve the issue. While the client can take action on certain error codes, the registry may add new error codes over time. All client implementations should treat unknown error codes as `UNKNOWN`, allowing future error codes to be added without breaking API compatibility. For the purposes of the specification error codes will only be added and never removed. For a complete account of all error codes, please see the [_Errors_](#errors-2) section. ### API Version Check A minimal endpoint, mounted at `/v2/` will provide version support information based on its response statuses. The request format is as follows: GET /v2/ If a `200 OK` response is returned, the registry implements the V2(.1) registry API and the client may proceed safely with other V2 operations. Optionally, the response may contain information about the supported paths in the response body. The client should be prepared to ignore this data. If a `401 Unauthorized` response is returned, the client should take action based on the contents of the "WWW-Authenticate" header and try the endpoint again. Depending on access control setup, the client may still have to authenticate against different resources, even if this check succeeds. If `404 Not Found` response status, or other unexpected status, is returned, the client should proceed with the assumption that the registry does not implement V2 of the API. When a `200 OK` or `401 Unauthorized` response is returned, the "Docker-Distribution-API-Version" header should be set to "registry/2.0". Clients may require this header value to determine if the endpoint serves this API. When this header is omitted, clients may fallback to an older API version. ### Content Digests This API design is driven heavily by [content addressability](http://en.wikipedia.org/wiki/Content-addressable_storage). The core of this design is the concept of a content addressable identifier. It uniquely identifies content by taking a collision-resistant hash of the bytes. Such an identifier can be independently calculated and verified by selection of a common _algorithm_. If such an identifier can be communicated in a secure manner, one can retrieve the content from an insecure source, calculate it independently and be certain that the correct content was obtained. Put simply, the identifier is a property of the content. To disambiguate from other concepts, we call this identifier a _digest_. A _digest_ is a serialized hash result, consisting of a _algorithm_ and _hex_ portion. The _algorithm_ identifies the methodology used to calculate the digest. The _hex_ portion is the hex-encoded result of the hash. We define a _digest_ string to match the following grammar: ``` digest := algorithm ":" hex algorithm := /[A-Fa-f0-9_+.-]+/ hex := /[A-Fa-f0-9]+/ ``` Some examples of _digests_ include the following: digest | description | ----------------------------------------------------------------------------------|------------------------------------------------ sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b | Common sha256 based digest | While the _algorithm_ does allow one to implement a wide variety of algorithms, compliant implementations should use sha256. Heavy processing of input before calculating a hash is discouraged to avoid degrading the uniqueness of the _digest_ but some canonicalization may be performed to ensure consistent identifiers. Let's use a simple example in pseudo-code to demonstrate a digest calculation: ``` let C = 'a small string' let B = sha256(C) let D = 'sha256:' + EncodeHex(B) let ID(C) = D ``` Above, we have bytestring `C` passed into a function, `SHA256`, that returns a bytestring `B`, which is the hash of `C`. `D` gets the algorithm concatenated with the hex encoding of `B`. We then define the identifier of `C` to `ID(C)` as equal to `D`. A digest can be verified by independently calculating `D` and comparing it with identifier `ID(C)`. #### Digest Header To provide verification of http content, any response may include a `Docker-Content-Digest` header. This will include the digest of the target entity returned in the response. For blobs, this is the entire blob content. For manifests, this is the manifest body without the signature content, also known as the JWS payload. Note that the commonly used canonicalization for digest calculation may be dependent on the mediatype of the content, such as with manifests. The client may choose to ignore the header or may verify it to ensure content integrity and transport security. This is most important when fetching by a digest. To ensure security, the content should be verified against the digest used to fetch the content. At times, the returned digest may differ from that used to initiate a request. Such digests are considered to be from different _domains_, meaning they have different values for _algorithm_. In such a case, the client may choose to verify the digests in both domains or ignore the server's digest. To maintain security, the client _must_ always verify the content against the _digest_ used to fetch the content. > __IMPORTANT:__ If a _digest_ is used to fetch content, the client should use > the same digest used to fetch the content to verify it. The header > `Docker-Content-Digest` should not be trusted over the "local" digest. ### Pulling An Image An "image" is a combination of a JSON manifest and individual layer files. The process of pulling an image centers around retrieving these two components. The first step in pulling an image is to retrieve the manifest. For reference, the relevant manifest fields for the registry are the following: field | description | ----------|------------------------------------------------| name | The name of the image. | tag | The tag for this version of the image. | fsLayers | A list of layer descriptors (including digest) | signature | A JWS used to verify the manifest content | For more information about the manifest format, please see [docker/docker#8093](https://github.com/docker/docker/issues/8093). When the manifest is in hand, the client must verify the signature to ensure the names and layers are valid. Once confirmed, the client will then use the digests to download the individual layers. Layers are stored in as blobs in the V2 registry API, keyed by their digest. #### Pulling an Image Manifest The image manifest can be fetched with the following url: ``` GET /v2//manifests/ ``` The `name` and `reference` parameter identify the image and are required. The reference may include a tag or digest. The client should include an Accept header indicating which manifest content types it supports. For more details on the manifest formats and their content types, see [manifest-v2-1.md](manifest-v2-1.md) and [manifest-v2-2.md](manifest-v2-2.md). In a successful response, the Content-Type header will indicate which manifest type is being returned. A `404 Not Found` response will be returned if the image is unknown to the registry. If the image exists and the response is successful, the image manifest will be returned, with the following format (see [docker/docker#8093](https://github.com/docker/docker/issues/8093) for details): { "name": , "tag": , "fsLayers": [ { "blobSum": }, ... ] ], "history": , "signature": } The client should verify the returned manifest signature for authenticity before fetching layers. ##### Existing Manifests The image manifest can be checked for existence with the following url: ``` HEAD /v2//manifests/ ``` The `name` and `reference` parameter identify the image and are required. The reference may include a tag or digest. A `404 Not Found` response will be returned if the image is unknown to the registry. If the image exists and the response is successful the response will be as follows: ``` 200 OK Content-Length: Docker-Content-Digest: ``` #### Pulling a Layer Layers are stored in the blob portion of the registry, keyed by digest. Pulling a layer is carried out by a standard http request. The URL is as follows: GET /v2//blobs/ Access to a layer will be gated by the `name` of the repository but is identified uniquely in the registry by `digest`. This endpoint may issue a 307 (302 for /blobs/uploads/ ``` The parameters of this request are the image namespace under which the layer will be linked. Responses to this request are covered below. ##### Existing Layers The existence of a layer can be checked via a `HEAD` request to the blob store API. The request should be formatted as follows: ``` HEAD /v2//blobs/ ``` If the layer with the digest specified in `digest` is available, a 200 OK response will be received, with no actual body content (this is according to http specification). The response will look as follows: ``` 200 OK Content-Length: Docker-Content-Digest: ``` When this response is received, the client can assume that the layer is already available in the registry under the given name and should take no further action to upload the layer. Note that the binary digests may differ for the existing registry layer, but the digests will be guaranteed to match. ##### Uploading the Layer If the POST request is successful, a `202 Accepted` response will be returned with the upload URL in the `Location` header: ``` 202 Accepted Location: /v2//blobs/uploads/ Range: bytes=0- Content-Length: 0 Docker-Upload-UUID: ``` The rest of the upload process can be carried out with the returned url, called the "Upload URL" from the `Location` header. All responses to the upload url, whether sending data or getting status, will be in this format. Though the URI format (`/v2//blobs/uploads/`) for the `Location` header is specified, clients should treat it as an opaque url and should never try to assemble it. While the `uuid` parameter may be an actual UUID, this proposal imposes no constraints on the format and clients should never impose any. If clients need to correlate local upload state with remote upload state, the contents of the `Docker-Upload-UUID` header should be used. Such an id can be used to key the last used location header when implementing resumable uploads. ##### Upload Progress The progress and chunk coordination of the upload process will be coordinated through the `Range` header. While this is a non-standard use of the `Range` header, there are examples of [similar approaches](https://developers.google.com/youtube/v3/guides/using_resumable_upload_protocol) in APIs with heavy use. For an upload that just started, for an example with a 1000 byte layer file, the `Range` header would be as follows: ``` Range: bytes=0-0 ``` To get the status of an upload, issue a GET request to the upload URL: ``` GET /v2//blobs/uploads/ Host: ``` The response will be similar to the above, except will return 204 status: ``` 204 No Content Location: /v2//blobs/uploads/ Range: bytes=0- Docker-Upload-UUID: ``` Note that the HTTP `Range` header byte ranges are inclusive and that will be honored, even in non-standard use cases. ##### Monolithic Upload A monolithic upload is simply a chunked upload with a single chunk and may be favored by clients that would like to avoided the complexity of chunking. To carry out a "monolithic" upload, one can simply put the entire content blob to the provided URL: ``` PUT /v2//blobs/uploads/?digest= Content-Length: Content-Type: application/octet-stream ``` The "digest" parameter must be included with the PUT request. Please see the [_Completed Upload_](#completed-upload) section for details on the parameters and expected responses. ##### Chunked Upload To carry out an upload of a chunk, the client can specify a range header and only include that part of the layer file: ``` PATCH /v2//blobs/uploads/ Content-Length: Content-Range: - Content-Type: application/octet-stream ``` There is no enforcement on layer chunk splits other than that the server must receive them in order. The server may enforce a minimum chunk size. If the server cannot accept the chunk, a `416 Requested Range Not Satisfiable` response will be returned and will include a `Range` header indicating the current status: ``` 416 Requested Range Not Satisfiable Location: /v2//blobs/uploads/ Range: 0- Content-Length: 0 Docker-Upload-UUID: ``` If this response is received, the client should resume from the "last valid range" and upload the subsequent chunk. A 416 will be returned under the following conditions: - Invalid Content-Range header format - Out of order chunk: the range of the next chunk must start immediately after the "last valid range" from the previous response. When a chunk is accepted as part of the upload, a `202 Accepted` response will be returned, including a `Range` header with the current upload status: ``` 202 Accepted Location: /v2//blobs/uploads/ Range: bytes=0- Content-Length: 0 Docker-Upload-UUID: ``` ##### Completed Upload For an upload to be considered complete, the client must submit a `PUT` request on the upload endpoint with a digest parameter. If it is not provided, the upload will not be considered complete. The format for the final chunk will be as follows: ``` PUT /v2//blob/uploads/?digest= Content-Length: Content-Range: - Content-Type: application/octet-stream ``` Optionally, if all chunks have already been uploaded, a `PUT` request with a `digest` parameter and zero-length body may be sent to complete and validated the upload. Multiple "digest" parameters may be provided with different digests. The server may verify none or all of them but _must_ notify the client if the content is rejected. When the last chunk is received and the layer has been validated, the client will receive a `201 Created` response: ``` 201 Created Location: /v2//blobs/ Content-Length: 0 Docker-Content-Digest: ``` The `Location` header will contain the registry URL to access the accepted layer file. The `Docker-Content-Digest` header returns the canonical digest of the uploaded blob which may differ from the provided digest. Most clients may ignore the value but if it is used, the client should verify the value against the uploaded blob data. ###### Digest Parameter The "digest" parameter is designed as an opaque parameter to support verification of a successful transfer. For example, a HTTP URI parameter might be as follows: ``` sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b ``` Given this parameter, the registry will verify that the provided content does match this digest. ##### Canceling an Upload An upload can be cancelled by issuing a DELETE request to the upload endpoint. The format will be as follows: ``` DELETE /v2//blobs/uploads/ ``` After this request is issued, the upload uuid will no longer be valid and the registry server will dump all intermediate data. While uploads will time out if not completed, clients should issue this request if they encounter a fatal error but still have the ability to issue an http request. ##### Cross Repository Blob Mount A blob may be mounted from another repository that the client has read access to, removing the need to upload a blob already known to the registry. To issue a blob mount instead of an upload, a POST request should be issued in the following format: ``` POST /v2//blobs/uploads/?mount=&from= Content-Length: 0 ``` If the blob is successfully mounted, the client will receive a `201 Created` response: ``` 201 Created Location: /v2//blobs/ Content-Length: 0 Docker-Content-Digest: ``` The `Location` header will contain the registry URL to access the accepted layer file. The `Docker-Content-Digest` header returns the canonical digest of the uploaded blob which may differ from the provided digest. Most clients may ignore the value but if it is used, the client should verify the value against the uploaded blob data. If a mount fails due to invalid repository or digest arguments, the registry will fall back to the standard upload behavior and return a `202 Accepted` with the upload URL in the `Location` header: ``` 202 Accepted Location: /v2//blobs/uploads/ Range: bytes=0- Content-Length: 0 Docker-Upload-UUID: ``` This behavior is consistent with older versions of the registry, which do not recognize the repository mount query parameters. Note: a client may issue a HEAD request to check existence of a blob in a source repository to distinguish between the registry not supporting blob mounts and the blob not existing in the expected repository. ##### Errors If an 502, 503 or 504 error is received, the client should assume that the download can proceed due to a temporary condition, honoring the appropriate retry mechanism. Other 5xx errors should be treated as terminal. If there is a problem with the upload, a 4xx error will be returned indicating the problem. After receiving a 4xx response (except 416, as called out above), the upload will be considered failed and the client should take appropriate action. Note that the upload url will not be available forever. If the upload uuid is unknown to the registry, a `404 Not Found` response will be returned and the client must restart the upload process. ### Deleting a Layer A layer may be deleted from the registry via its `name` and `digest`. A delete may be issued with the following request format: DELETE /v2//blobs/ If the blob exists and has been successfully deleted, the following response will be issued: 202 Accepted Content-Length: None If the blob had already been deleted or did not exist, a `404 Not Found` response will be issued instead. If a layer is deleted which is referenced by a manifest in the registry, then the complete images will not be resolvable. #### Pushing an Image Manifest Once all of the layers for an image are uploaded, the client can upload the image manifest. An image can be pushed using the following request format: PUT /v2//manifests/ Content-Type: { "name": , "tag": , "fsLayers": [ { "blobSum": }, ... ] ], "history": , "signature": , ... } The `name` and `reference` fields of the response body must match those specified in the URL. The `reference` field may be a "tag" or a "digest". The content type should match the type of the manifest being uploaded, as specified in [manifest-v2-1.md](manifest-v2-1.md) and [manifest-v2-2.md](manifest-v2-2.md). If there is a problem with pushing the manifest, a relevant 4xx response will be returned with a JSON error message. Please see the [_PUT Manifest_](#put-manifest) section for details on possible error codes that may be returned. If one or more layers are unknown to the registry, `BLOB_UNKNOWN` errors are returned. The `detail` field of the error response will have a `digest` field identifying the missing blob. An error is returned for each unknown blob. The response format is as follows: { "errors:" [{ "code": "BLOB_UNKNOWN", "message": "blob unknown to registry", "detail": { "digest": } }, ... ] } ### Listing Repositories Images are stored in collections, known as a _repository_, which is keyed by a `name`, as seen throughout the API specification. A registry instance may contain several repositories. The list of available repositories is made available through the _catalog_. The catalog for a given registry can be retrieved with the following request: ``` GET /v2/_catalog ``` The response will be in the following format: ``` 200 OK Content-Type: application/json { "repositories": [ , ... ] } ``` Note that the contents of the response are specific to the registry implementation. Some registries may opt to provide a full catalog output, limit it based on the user's access level or omit upstream results, if providing mirroring functionality. Subsequently, the presence of a repository in the catalog listing only means that the registry *may* provide access to the repository at the time of the request. Conversely, a missing entry does *not* mean that the registry does not have the repository. More succinctly, the presence of a repository only guarantees that it is there but not that it is _not_ there. For registries with a large number of repositories, this response may be quite large. If such a response is expected, one should use pagination. A registry may also limit the amount of responses returned even if pagination was not explicitly requested. In this case the `Link` header will be returned along with the results, and subsequent results can be obtained by following the link as if pagination had been initially requested. For details of the `Link` header, please see the [_Pagination_](#pagination) section. #### Pagination Paginated catalog results can be retrieved by adding an `n` parameter to the request URL, declaring that the response should be limited to `n` results. Starting a paginated flow begins as follows: ``` GET /v2/_catalog?n= ``` The above specifies that a catalog response should be returned, from the start of the result set, ordered lexically, limiting the number of results to `n`. The response to such a request would look as follows: ``` 200 OK Content-Type: application/json Link: <?n=&last=>; rel="next" { "repositories": [ , ... ] } ``` The above includes the _first_ `n` entries from the result set. To get the _next_ `n` entries, one can create a URL where the argument `last` has the value from `repositories[len(repositories)-1]`. If there are indeed more results, the URL for the next block is encoded in an [RFC5988](https://tools.ietf.org/html/rfc5988) `Link` header, as a "next" relation. The presence of the `Link` header communicates to the client that the entire result set has not been returned and another request must be issued. If the header is not present, the client can assume that all results have been received. > __NOTE:__ In the request template above, note that the brackets > are required. For example, if the url is > `http://example.com/v2/_catalog?n=20&last=b`, the value of the header would > be `; rel="next"`. Please see > [RFC5988](https://tools.ietf.org/html/rfc5988) for details. Compliant client implementations should always use the `Link` header value when proceeding through results linearly. The client may construct URLs to skip forward in the catalog. To get the next result set, a client would issue the request as follows, using the URL encoded in the described `Link` header: ``` GET /v2/_catalog?n=&last= ``` The above process should then be repeated until the `Link` header is no longer set. The catalog result set is represented abstractly as a lexically sorted list, where the position in that list can be specified by the query term `last`. The entries in the response start _after_ the term specified by `last`, up to `n` entries. The behavior of `last` is quite simple when demonstrated with an example. Let us say the registry has the following repositories: ``` a b c d ``` If the value of `n` is 2, _a_ and _b_ will be returned on the first response. The `Link` header returned on the response will have `n` set to 2 and last set to _b_: ``` Link: <?n=2&last=b>; rel="next" ``` The client can then issue the request with the above value from the `Link` header, receiving the values _c_ and _d_. Note that `n` may change on the second to last response or be fully omitted, depending on the server implementation. ### Listing Image Tags It may be necessary to list all of the tags under a given repository. The tags for an image repository can be retrieved with the following request: GET /v2//tags/list The response will be in the following format: 200 OK Content-Type: application/json { "name": , "tags": [ , ... ] } For repositories with a large number of tags, this response may be quite large. If such a response is expected, one should use the pagination. #### Pagination Paginated tag results can be retrieved by adding the appropriate parameters to the request URL described above. The behavior of tag pagination is identical to that specified for catalog pagination. We cover a simple flow to highlight any differences. Starting a paginated flow may begin as follows: ``` GET /v2//tags/list?n= ``` The above specifies that a tags response should be returned, from the start of the result set, ordered lexically, limiting the number of results to `n`. The response to such a request would look as follows: ``` 200 OK Content-Type: application/json Link: <?n=&last=>; rel="next" { "name": , "tags": [ , ... ] } ``` To get the next result set, a client would issue the request as follows, using the value encoded in the [RFC5988](https://tools.ietf.org/html/rfc5988) `Link` header: ``` GET /v2//tags/list?n=&last= ``` The above process should then be repeated until the `Link` header is no longer set in the response. The behavior of the `last` parameter, the provided response result, lexical ordering and encoding of the `Link` header are identical to that of catalog pagination. ### Deleting an Image An image may be deleted from the registry via its `name` and `reference`. A delete may be issued with the following request format: DELETE /v2//manifests/ For deletes, `reference` *must* be a digest or the delete will fail. If the image exists and has been successfully deleted, the following response will be issued: 202 Accepted Content-Length: None If the image had already been deleted or did not exist, a `404 Not Found` response will be issued instead. > **Note** When deleting a manifest from a registry version 2.3 or later, the > following header must be used when `HEAD` or `GET`-ing the manifest to obtain > the correct digest to delete: Accept: application/vnd.docker.distribution.manifest.v2+json > for more details, see: [compatibility.md](../compatibility.md#content-addressable-storage-cas) ## Detail > **Note**: This section is still under construction. For the purposes of > implementation, if any details below differ from the described request flows > above, the section below should be corrected. When they match, this note > should be removed. The behavior of the endpoints are covered in detail in this section, organized by route and entity. All aspects of the request and responses are covered, including headers, parameters and body formats. Examples of requests and their corresponding responses, with success and failure, are enumerated. > **Note**: The sections on endpoint detail are arranged with an example > request, a description of the request, followed by information about that > request. A list of methods and URIs are covered in the table below: |Method|Path|Entity|Description| |------|----|------|-----------| {{range $route := .RouteDescriptors}}{{range $method := .Methods}}| {{$method.Method}} | `{{$route.Path|prettygorilla}}` | {{$route.Entity}} | {{$method.Description}} | {{end}}{{end}} The detail for each endpoint is covered in the following sections. ### Errors The error codes encountered via the API are enumerated in the following table: |Code|Message|Description| |----|-------|-----------| {{range $err := .ErrorDescriptors}} `{{$err.Value}}` | {{$err.Message}} | {{$err.Description|removenewlines}} {{end}} {{range $route := .RouteDescriptors}} ### {{.Entity}} {{.Description}} {{range $method := $route.Methods}} #### {{.Method}} {{$route.Entity}} {{.Description}} {{if .Requests}}{{range .Requests}}{{if .Name}} ##### {{.Name}}{{end}} ``` {{$method.Method}} {{$route.Path|prettygorilla}}{{range $i, $param := .QueryParameters}}{{if eq $i 0}}?{{else}}&{{end}}{{$param.Name}}={{$param.Format}}{{end}}{{range .Headers}} {{.Name}}: {{.Format}}{{end}}{{if .Body.ContentType}} Content-Type: {{.Body.ContentType}}{{end}}{{if .Body.Format}} {{.Body.Format}}{{end}} ``` {{.Description}} {{if or .Headers .PathParameters .QueryParameters}} The following parameters should be specified on the request: |Name|Kind|Description| |----|----|-----------| {{range .Headers}}|`{{.Name}}`|header|{{.Description}}| {{end}}{{range .PathParameters}}|`{{.Name}}`|path|{{.Description}}| {{end}}{{range .QueryParameters}}|`{{.Name}}`|query|{{.Description}}| {{end}}{{end}} {{if .Successes}} {{range .Successes}} ###### On Success: {{if .Name}}{{.Name}}{{else}}{{.StatusCode | statustext}}{{end}} ``` {{.StatusCode}} {{.StatusCode | statustext}}{{range .Headers}} {{.Name}}: {{.Format}}{{end}}{{if .Body.ContentType}} Content-Type: {{.Body.ContentType}}{{end}}{{if .Body.Format}} {{.Body.Format}}{{end}} ``` {{.Description}} {{if .Fields}}The following fields may be returned in the response body: |Name|Description| |----|-----------| {{range .Fields}}|`{{.Name}}`|{{.Description}}| {{end}}{{end}}{{if .Headers}} The following headers will be returned with the response: |Name|Description| |----|-----------| {{range .Headers}}|`{{.Name}}`|{{.Description}}| {{end}}{{end}}{{end}}{{end}} {{if .Failures}} {{range .Failures}} ###### On Failure: {{if .Name}}{{.Name}}{{else}}{{.StatusCode | statustext}}{{end}} ``` {{.StatusCode}} {{.StatusCode | statustext}}{{range .Headers}} {{.Name}}: {{.Format}}{{end}}{{if .Body.ContentType}} Content-Type: {{.Body.ContentType}}{{end}}{{if .Body.Format}} {{.Body.Format}}{{end}} ``` {{.Description}} {{if .Headers}} The following headers will be returned on the response: |Name|Description| |----|-----------| {{range .Headers}}|`{{.Name}}`|{{.Description}}| {{end}}{{end}} {{if .ErrorCodes}} The error codes that may be included in the response body are enumerated below: |Code|Message|Description| |----|-------|-----------| {{range $err := .ErrorCodes}}| `{{$err.Descriptor.Value}}` | {{$err.Descriptor.Message}} | {{$err.Descriptor.Description|removenewlines}} | {{end}} {{end}}{{end}}{{end}}{{end}}{{end}}{{end}} {{end}}