summaryrefslogtreecommitdiff
path: root/doc/administration/container_registry.md
blob: 4d55f2357c18d8f3d213d98b095a617008e0d45d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
# GitLab Container Registry administration

> **Notes:**
>
> - [Introduced][ce-4040] in GitLab 8.8.
> - Container Registry manifest `v1` support was added in GitLab 8.9 to support
>   Docker versions earlier than 1.10.
> - This document is about the admin guide. To learn how to use GitLab Container
>   Registry [user documentation](../user/project/container_registry.md).

With the Container Registry integrated into GitLab, every project can have its
own space to store its Docker images.

You can read more about the Container Registry at
<https://docs.docker.com/registry/introduction/>.

## Enable the Container Registry

**Omnibus GitLab installations**

All you have to do is configure the domain name under which the Container
Registry will listen to. Read
[#container-registry-domain-configuration](#container-registry-domain-configuration)
and pick one of the two options that fits your case.

>**Note:**
The container registry works under HTTPS by default. Using HTTP is possible
but not recommended and out of the scope of this document.
Read the [insecure Registry documentation][docker-insecure] if you want to
implement this.

---

**Installations from source**

If you have installed GitLab from source:

1. You will have to [install Registry][registry-deploy] by yourself.
1. After the installation is complete, you will have to configure the Registry's
   settings in `gitlab.yml` in order to enable it.
1. Use the sample NGINX configuration file that is found under
   [`lib/support/nginx/registry-ssl`][registry-ssl] and edit it to match the
   `host`, `port` and TLS certs paths.

The contents of `gitlab.yml` are:

```
registry:
  enabled: true
  host: registry.gitlab.example.com
  port: 5005
  api_url: http://localhost:5000/
  key: config/registry.key
  path: shared/registry
  issuer: gitlab-issuer
```

where:

| Parameter | Description |
| --------- | ----------- |
| `enabled` | `true` or `false`. Enables the Registry in GitLab. By default this is `false`. |
| `host`    | The host URL under which the Registry will run and the users will be able to use. |
| `port`    | The port under which the external Registry domain will listen on. |
| `api_url` | The internal API URL under which the Registry is exposed to. It defaults to `http://localhost:5000`. |
| `key`     | The private key location that is a pair of Registry's `rootcertbundle`. Read the [token auth configuration documentation][token-config]. |
| `path`    | This should be the same directory like specified in Registry's `rootdirectory`. Read the [storage configuration documentation][storage-config]. This path needs to be readable by the GitLab user, the web-server user and the Registry user. Read more in [#container-registry-storage-path](#container-registry-storage-path). |
| `issuer`  | This should be the same value as configured in Registry's `issuer`. Read the [token auth configuration documentation][token-config]. |

>**Note:**
A Registry init file is not shipped with GitLab if you install it from source.
Hence, [restarting GitLab][restart gitlab] will not restart the Registry should
you modify its settings. Read the upstream documentation on how to achieve that.

At the **absolute** minimum, make sure your [Registry configuration][registry-auth]
has `container_registry` as the service and `https://gitlab.example.com/jwt/auth`
as the realm:

```
auth:
  token:
    realm: https://gitlab.example.com/jwt/auth
    service: container_registry
    issuer: gitlab-issuer
    rootcertbundle: /root/certs/certbundle
```

CAUTION: **Caution:**
If `auth` is not set up, users will be able to pull docker images without authentication.

## Container Registry domain configuration

There are two ways you can configure the Registry's external domain.

- Either [use the existing GitLab domain][existing-domain] where in that case
  the Registry will have to listen on a port and reuse GitLab's TLS certificate,
- or [use a completely separate domain][new-domain] with a new TLS certificate
  for that domain.

Since the container Registry requires a TLS certificate, in the end it all boils
down to how easy or pricey is to get a new one.

Please take this into consideration before configuring the Container Registry
for the first time.

### Configure Container Registry under an existing GitLab domain

If the Registry is configured to use the existing GitLab domain, you can
expose the Registry on a port so that you can reuse the existing GitLab TLS
certificate.

Assuming that the GitLab domain is `https://gitlab.example.com` and the port the
Registry is exposed to the outside world is `4567`, here is what you need to set
in `gitlab.rb` or `gitlab.yml` if you are using Omnibus GitLab or installed
GitLab from source respectively.

>**Note:**
Be careful to choose a port different than the one that Registry listens to (`5000` by default),
otherwise you will run into conflicts.

---

**Omnibus GitLab installations**

1. Your `/etc/gitlab/gitlab.rb` should contain the Registry URL as well as the
   path to the existing TLS certificate and key used by GitLab:

    ```ruby
    registry_external_url 'https://gitlab.example.com:4567'
    ```

    Note how the `registry_external_url` is listening on HTTPS under the
    existing GitLab URL, but on a different port.

    If your TLS certificate is not in `/etc/gitlab/ssl/gitlab.example.com.crt`
    and key not in `/etc/gitlab/ssl/gitlab.example.com.key` uncomment the lines
    below:

    ```ruby
    registry_nginx['ssl_certificate'] = "/path/to/certificate.pem"
    registry_nginx['ssl_certificate_key'] = "/path/to/certificate.key"
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**Installations from source**

1. Open `/home/git/gitlab/config/gitlab.yml`, find the `registry` entry and
   configure it with the following settings:

    ```
    registry:
      enabled: true
      host: gitlab.example.com
      port: 4567
    ```

1. Save the file and [restart GitLab][] for the changes to take effect.
1. Make the relevant changes in NGINX as well (domain, port, TLS certificates path).

---

Users should now be able to login to the Container Registry with their GitLab
credentials using:

```bash
docker login gitlab.example.com:4567
```

### Configure Container Registry under its own domain

If the Registry is configured to use its own domain, you will need a TLS
certificate for that specific domain (e.g., `registry.example.com`) or maybe
a wildcard certificate if hosted under a subdomain  of your existing GitLab
domain (e.g., `registry.gitlab.example.com`).

Let's assume that you want the container Registry to be accessible at
`https://registry.gitlab.example.com`.

---

**Omnibus GitLab installations**

1. Place your TLS certificate and key in
   `/etc/gitlab/ssl/registry.gitlab.example.com.crt` and
   `/etc/gitlab/ssl/registry.gitlab.example.com.key` and make sure they have
   correct permissions:

    ```bash
    chmod 600 /etc/gitlab/ssl/registry.gitlab.example.com.*
    ```

1. Once the TLS certificate is in place, edit `/etc/gitlab/gitlab.rb` with:

    ```ruby
    registry_external_url 'https://registry.gitlab.example.com'
    ```

    Note how the `registry_external_url` is listening on HTTPS.

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

> **Note:**
If you have a [wildcard certificate][], you need to specify the path to the
certificate in addition to the URL, in this case `/etc/gitlab/gitlab.rb` will
look like:
>
> ```ruby
> registry_nginx['ssl_certificate'] = "/etc/gitlab/ssl/certificate.pem"
> registry_nginx['ssl_certificate_key'] = "/etc/gitlab/ssl/certificate.key"
> ```

---

**Installations from source**

1. Open `/home/git/gitlab/config/gitlab.yml`, find the `registry` entry and
   configure it with the following settings:

    ```
    registry:
      enabled: true
      host: registry.gitlab.example.com
    ```

1. Save the file and [restart GitLab][] for the changes to take effect.
1. Make the relevant changes in NGINX as well (domain, port, TLS certificates path).

---

Users should now be able to login to the Container Registry using their GitLab
credentials:

```bash
docker login registry.gitlab.example.com
```

## Disable Container Registry site-wide

>**Note:**
Disabling the Registry in the Rails GitLab application as set by the following
steps, will not remove any existing Docker images. This is handled by the
Registry application itself.

**Omnibus GitLab**

1. Open `/etc/gitlab/gitlab.rb` and set `registry['enable']` to `false`:

    ```ruby
    registry['enable'] = false
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**Installations from source**

1. Open `/home/git/gitlab/config/gitlab.yml`, find the `registry` entry and
   set `enabled` to `false`:

    ```
    registry:
      enabled: false
    ```

1. Save the file and [restart GitLab][] for the changes to take effect.

## Disable Container Registry for new projects site-wide

If the Container Registry is enabled, then it will be available on all new
projects. To disable this function and let the owners of a project to enable
the Container Registry by themselves, follow the steps below.

---

**Omnibus GitLab installations**

1. Edit `/etc/gitlab/gitlab.rb` and add the following line:

    ```ruby
    gitlab_rails['gitlab_default_projects_features_container_registry'] = false
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**Installations from source**

1. Open `/home/git/gitlab/config/gitlab.yml`, find the `default_projects_features`
   entry and configure it so that `container_registry` is set to `false`:

    ```
    ## Default project features settings
    default_projects_features:
      issues: true
      merge_requests: true
      wiki: true
      snippets: false
      builds: true
      container_registry: false
    ```

1. Save the file and [restart GitLab][] for the changes to take effect.

## Container Registry storage path

>**Note:**
For configuring storage in the cloud instead of the filesystem, see the
[storage driver configuration](#container-registry-storage-driver).

If you want to store your images on the filesystem, you can change the storage
path for the Container Registry, follow the steps below.

This path is accessible to:

- the user running the Container Registry daemon,
- the user running GitLab

> **Warning** You should confirm that all GitLab, Registry and web server users
have access to this directory.

---

**Omnibus GitLab installations**

The default location where images are stored in Omnibus, is
`/var/opt/gitlab/gitlab-rails/shared/registry`. To change it:

1. Edit `/etc/gitlab/gitlab.rb`:

    ```ruby
    gitlab_rails['registry_path'] = "/path/to/registry/storage"
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**Installations from source**

The default location where images are stored in source installations, is
`/home/git/gitlab/shared/registry`. To change it:

1. Open `/home/git/gitlab/config/gitlab.yml`, find the `registry` entry and
   change the `path` setting:

    ```
    registry:
      path: shared/registry
    ```

1. Save the file and [restart GitLab][] for the changes to take effect.

## Container Registry storage driver

You can configure the Container Registry to use a different storage backend by
configuring a different storage driver. By default the GitLab Container Registry
is configured to use the filesystem driver, which makes use of [storage path](#container-registry-storage-path)
configuration.

NOTE: **Note:** Enabling a storage driver other than `filesystem` would mean
that your Docker client needs to be able to access the storage backend directly.
In that case, you must use an address that resolves and is accessible outside GitLab server.

The different supported drivers are:

| Driver     | Description                         |
|------------|-------------------------------------|
| filesystem | Uses a path on the local filesystem |
| azure      | Microsoft Azure Blob Storage        |
| gcs        | Google Cloud Storage                |
| s3         | Amazon Simple Storage Service. Be sure to configure your storage bucket with the correct [S3 Permission Scopes](https://docs.docker.com/registry/storage-drivers/s3/#s3-permission-scopes).       |
| swift      | OpenStack Swift Object Storage      |
| oss        | Aliyun OSS                          |

Read more about the individual driver's config options in the
[Docker Registry docs][storage-config].

CAUTION: **Warning:** GitLab will not backup Docker images that are not stored on the
filesystem. Remember to enable backups with your object storage provider if
desired.

NOTE: **Note:**
`regionendpoint` is only required when configuring an S3 compatible service such as Minio. It takes a URL such as `http://127.0.0.1:9000`.

**Omnibus GitLab installations**

To configure the `s3` storage driver in Omnibus:

1. Edit `/etc/gitlab/gitlab.rb`:

    ```ruby
    registry['storage'] = {
      's3' => {
        'accesskey' => 's3-access-key',
        'secretkey' => 's3-secret-key-for-access-key',
        'bucket' => 'your-s3-bucket',
        'region' => 'your-s3-region',
        'regionendpoint' => 'your-s3-regionendpoint'
      }
    }
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

**Installations from source**

Configuring the storage driver is done in your registry config YML file created
when you [deployed your docker registry][registry-deploy].

`s3` storage driver example:

```yml
storage:
  s3:
    accesskey: 'AKIAKIAKI'
    secretkey: 'secret123'
    bucket: 'gitlab-registry-bucket-AKIAKIAKI'
    region: 'your-s3-region'
    regionendpoint: 'your-s3-regionendpoint'
  cache:
    blobdescriptor: inmemory
  delete:
    enabled: true
```

## Change the registry's internal port

> **Note:**
This is not to be confused with the port that GitLab itself uses to expose
the Registry to the world.

The Registry server listens on localhost at port `5000` by default,
which is the address for which the Registry server should accept connections.
In the examples below we set the Registry's port to `5001`.

**Omnibus GitLab**

1. Open `/etc/gitlab/gitlab.rb` and set `registry['registry_http_addr']`:

    ```ruby
    registry['registry_http_addr'] = "localhost:5001"
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**Installations from source**

1. Open the configuration file of your Registry server and edit the
   [`http:addr`][registry-http-config] value:

    ```
    http
      addr: localhost:5001
    ```

1. Save the file and restart the Registry server.

## Disable Container Registry per project

If Registry is enabled in your GitLab instance, but you don't need it for your
project, you can disable it from your project's settings. Read the user guide
on how to achieve that.

## Disable Container Registry but use GitLab as an auth endpoint

**Omnibus GitLab**

You can use GitLab as an auth endpoint and use a non-bundled Container Registry.

1. Open `/etc/gitlab/gitlab.rb` and set necessary configurations:

    ```ruby
    gitlab_rails['registry_enabled'] = true
    gitlab_rails['registry_host'] = "registry.gitlab.example.com"
    gitlab_rails['registry_port'] = "5005"
    gitlab_rails['registry_api_url'] = "http://localhost:5000"
    gitlab_rails['registry_path'] = "/var/opt/gitlab/gitlab-rails/shared/registry"
    gitlab_rails['registry_issuer'] = "omnibus-gitlab-issuer"
    ```

1. A certificate keypair is required for GitLab and the Container Registry to
   communicate securely.  By default omnibus-gitlab will generate one keypair,
   which is saved to `/var/opt/gitlab/gitlab-rails/etc/gitlab-registry.key`.
   When using a non-bundled Container Registry, you will need to supply a
   custom certificate key. To do that, add the following to
   `/etc/gitlab/gitlab.rb`

    ```ruby
    gitlab_rails['registry_key_path'] = "/custom/path/to/registry-key.key"
    # registry['internal_key'] should contain the contents of the custom key
    # file. Line breaks in the key file should be marked using `\n` character
    # Example:
    registry['internal_key'] = "---BEGIN RSA PRIVATE KEY---\nMIIEpQIBAA\n"
    ```

    **Note:** The file specified at `registry_key_path` gets populated with the
    content specified by `internal_key`, each time reconfigure is executed. If
    no file is specified, omnibus-gitlab will default it to
    `/var/opt/gitlab/gitlab-rails/etc/gitlab-registry.key` and will populate
    it.

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

**Installations from source**

1. Open `/home/git/gitlab/config/gitlab.yml`, and edit the configuration settings under `registry`:

    ```
    ## Container Registry

    registry:
      enabled: true
      host: "registry.gitlab.example.com"
      port: "5005"
      api_url: "http://localhost:5000"
      path: /var/opt/gitlab/gitlab-rails/shared/registry
      key: /var/opt/gitlab/gitlab-rails/certificate.key
      issuer: omnibus-gitlab-issuer
    ```

1. Save the file and [restart GitLab][] for the changes to take effect.

## Storage limitations

Currently, there is no storage limitation, which means a user can upload an
infinite amount of Docker images with arbitrary sizes. This setting will be
configurable in future releases.

## Configure Container Registry notifications

You can configure the Container Registry to send webhook notifications in
response to events happening within the registry.

Read more about the Container Registry notifications config options in the
[Docker Registry notifications documentation][notifications-config].

>**Note:**
Multiple endpoints can be configured for the Container Registry.

**Omnibus GitLab installations**

To configure a notification endpoint in Omnibus:

1. Edit `/etc/gitlab/gitlab.rb`:

    ```ruby
    registry['notifications'] = [
      {
        'name' => 'test_endpoint',
        'url' => 'https://gitlab.example.com/notify',
        'timeout' => '500ms',
        'threshold' => 5,
        'backoff' => '1s',
        'headers' => {
          "Authorization" => ["AUTHORIZATION_EXAMPLE_TOKEN"]
        }
      }
    ]
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**Installations from source**

Configuring the notification endpoint is done in your registry config YML file created
when you [deployed your docker registry][registry-deploy].

Example:

```
notifications:
  endpoints:
    - name: alistener
      disabled: false
      url: https://my.listener.com/event
      headers: <http.Header>
      timeout: 500
      threshold: 5
      backoff: 1000
```

## Troubleshooting

### Using self-signed certificates with Container Registry

If you're using a self-signed certificate with your Container Registry, you
might encounter issues during the CI jobs like the following:

```
Error response from daemon: Get registry.example.com/v1/users/: x509: certificate signed by unknown authority
```

The Docker daemon running the command expects a cert signed by a recognized CA,
thus the error above.

While GitLab doesn't support using self-signed certificates with Container Registry out of the box, it is possible to make it work by [instructing the docker-daemon to trust the self-signed certificates][docker-insecure-self-signed], mounting the docker-daemon and setting `privileged = false` in the runner's `config.toml`. Setting `privileged = true` takes precedence over the docker-daemon.

```
  [runners.docker]
    image = "ruby:2.1"
    privileged = false
    volumes = ["/var/run/docker.sock:/var/run/docker.sock", "/cache"]
```

Additional information about this: [issue 18239][ce-18239].

### AWS S3 with the GitLab registry error when pushing large images

When using AWS S3 with the GitLab registry, an error may occur when pushing
large images. Look in the Registry log for the following error:

```
level=error msg="response completed with error" err.code=unknown err.detail="unexpected EOF" err.message="unknown error"
```

To resolve the error specify a `chunksize` value in the Registry configuration.
Start with a value between `25000000` (25MB) and `50000000` (50MB).

**For Omnibus installations**

1. Edit `/etc/gitlab/gitlab.rb`:

    ```ruby
    registry['storage'] = {
      's3' => {
        'accesskey' => 'AKIAKIAKI',
        'secretkey' => 'secret123',
        'bucket'    => 'gitlab-registry-bucket-AKIAKIAKI',
        'chunksize' => 25000000
      }
    }
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**For installations from source**

1. Edit `config/gitlab.yml`:

    ```yaml
    storage:
      s3:
        accesskey: 'AKIAKIAKI'
        secretkey: 'secret123'
        bucket:    'gitlab-registry-bucket-AKIAKIAKI'
        chunksize: 25000000
    ```

1. Save the file and [restart GitLab][] for the changes to take effect.

### Supporting older Docker clients

As of GitLab 11.9, we began shipping version 2.7.1 of the Docker container registry, which disables the schema1 manifest by default. If you are still using older Docker clients (1.9 or older), you may experience an error pushing images. See [omnibus-4145](https://gitlab.com/gitlab-org/omnibus-gitlab/issues/4145) for more details.

You can add a configuration option for backwards compatibility.

**For Omnibus installations**

1. Edit `/etc/gitlab/gitlab.rb`:

    ```ruby
    registry['compatibility_schema1_enabled'] = true
    ```

1. Save the file and [reconfigure GitLab][] for the changes to take effect.

---

**For installations from source**

1. Edit the YML configuration file you created when you [deployed the registry][registry-deploy]. Add the following snippet:

    ```yaml
    compatibility:
        schema1:
            enabled: true
    ```

1. Restart the registry for the changes to take affect.


[ce-18239]: https://gitlab.com/gitlab-org/gitlab-ce/issues/18239
[docker-insecure-self-signed]: https://docs.docker.com/registry/insecure/#use-self-signed-certificates
[reconfigure gitlab]: restart_gitlab.md#omnibus-gitlab-reconfigure
[restart gitlab]: restart_gitlab.md#installations-from-source
[wildcard certificate]: https://en.wikipedia.org/wiki/Wildcard_certificate
[ce-4040]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4040
[docker-insecure]: https://docs.docker.com/registry/insecure/
[registry-deploy]: https://docs.docker.com/registry/deploying/
[storage-config]: https://docs.docker.com/registry/configuration/#storage
[registry-http-config]: https://docs.docker.com/registry/configuration/#http
[registry-auth]: https://docs.docker.com/registry/configuration/#auth
[token-config]: https://docs.docker.com/registry/configuration/#token
[8-8-docs]: https://gitlab.com/gitlab-org/gitlab-ce/blob/8-8-stable/doc/administration/container_registry.md
[registry-ssl]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/lib/support/nginx/registry-ssl
[existing-domain]: #configure-container-registry-under-an-existing-gitlab-domain
[new-domain]: #configure-container-registry-under-its-own-domain
[notifications-config]: https://docs.docker.com/registry/notifications/
[registry-notifications-config]: https://docs.docker.com/registry/configuration/#notifications