forked from TrueCloudLab/distribution
132 lines
5 KiB
Markdown
132 lines
5 KiB
Markdown
---
|
|
description: Setting-up a local mirror for Docker Hub images
|
|
keywords: registry, on-prem, images, tags, repository, distribution, mirror, Hub, recipe, advanced
|
|
title: Registry as a pull through cache
|
|
redirect_from:
|
|
- /engine/admin/registry_mirror/
|
|
---
|
|
|
|
{% include registry.md %}
|
|
|
|
## Use-case
|
|
|
|
If you have multiple instances of Docker running in your environment, such as
|
|
multiple physical or virtual machines all running Docker, each daemon goes out
|
|
to the internet and fetches an image it doesn't have locally, from the Docker
|
|
repository. You can run a local registry mirror and point all your daemons
|
|
there, to avoid this extra internet traffic.
|
|
|
|
> **Note**
|
|
>
|
|
> Docker Official Images are an intellectual property of Docker. Distributing Docker Official Images to third parties without a prior agreement can constitute a violation of [Docker Terms of Service](https://www.docker.com/legal/docker-terms-service){: target="blank" rel="noopener" class=“”}.
|
|
|
|
### Alternatives
|
|
|
|
Alternatively, if the set of images you are using is well delimited, you can
|
|
simply pull them manually and push them to a simple, local, private registry.
|
|
|
|
Furthermore, if your images are all built in-house, not using the Hub at all and
|
|
relying entirely on your local registry is the simplest scenario.
|
|
|
|
### Gotcha
|
|
|
|
It's currently not possible to mirror another private registry. Only the central
|
|
Hub can be mirrored.
|
|
|
|
> **Note**
|
|
>
|
|
> Mirrors of Docker Hub are still subject to Docker's [fair usage policy](https://www.docker.com/pricing/resource-consumption-updates){: target="blank" rel="noopener" class=“”}.
|
|
|
|
### Solution
|
|
|
|
The Registry can be configured as a pull through cache. In this mode a Registry
|
|
responds to all normal docker pull requests but stores all content locally.
|
|
|
|
## How does it work?
|
|
|
|
The first time you request an image from your local registry mirror, it pulls
|
|
the image from the public Docker registry and stores it locally before handing
|
|
it back to you. On subsequent requests, the local registry mirror is able to
|
|
serve the image from its own storage.
|
|
|
|
### What if the content changes on the Hub?
|
|
|
|
When a pull is attempted with a tag, the Registry checks the remote to
|
|
ensure if it has the latest version of the requested content. Otherwise, it
|
|
fetches and caches the latest content.
|
|
|
|
### What about my disk?
|
|
|
|
In environments with high churn rates, stale data can build up in the cache.
|
|
When running as a pull through cache the Registry periodically removes old
|
|
content to save disk space. Subsequent requests for removed content causes a
|
|
remote fetch and local re-caching.
|
|
|
|
To ensure best performance and guarantee correctness the Registry cache should
|
|
be configured to use the `filesystem` driver for storage.
|
|
|
|
## Run a Registry as a pull-through cache
|
|
|
|
The easiest way to run a registry as a pull through cache is to run the official
|
|
Registry image.
|
|
At least, you need to specify `proxy.remoteurl` within `/etc/docker/registry/config.yml`
|
|
as described in the following subsection.
|
|
|
|
Multiple registry caches can be deployed over the same back-end. A single
|
|
registry cache ensures that concurrent requests do not pull duplicate data,
|
|
but this property does not hold true for a registry cache cluster.
|
|
|
|
> **Note**
|
|
>
|
|
> Service accounts included in the Team plan are limited to 5,000 pulls per day. See [Service Accounts](/docker-hub/service-accounts/) for more details.
|
|
|
|
### Configure the cache
|
|
|
|
To configure a Registry to run as a pull through cache, the addition of a
|
|
`proxy` section is required to the config file.
|
|
|
|
To access private images on the Docker Hub, a username and password can
|
|
be supplied.
|
|
|
|
```yaml
|
|
proxy:
|
|
remoteurl: https://registry-1.docker.io
|
|
username: [username]
|
|
password: [password]
|
|
```
|
|
|
|
> **Warning**: If you specify a username and password, it's very important to
|
|
> understand that private resources that this user has access to Docker Hub is
|
|
> made available on your mirror. **You must secure your mirror** by
|
|
> implementing authentication if you expect these resources to stay private!
|
|
|
|
> **Warning**: For the scheduler to clean up old entries, `delete` must
|
|
> be enabled in the registry configuration. See
|
|
> [Registry Configuration](../configuration.md) for more details.
|
|
|
|
### Configure the Docker daemon
|
|
|
|
Either pass the `--registry-mirror` option when starting `dockerd` manually,
|
|
or edit [`/etc/docker/daemon.json`](../../engine/reference/commandline/dockerd.md#daemon-configuration-file)
|
|
and add the `registry-mirrors` key and value, to make the change persistent.
|
|
|
|
```json
|
|
{
|
|
"registry-mirrors": ["https://<my-docker-mirror-host>"]
|
|
}
|
|
```
|
|
|
|
Save the file and reload Docker for the change to take effect.
|
|
|
|
> Some log messages that appear to be errors are actually informational messages.
|
|
>
|
|
> Check the `level` field to determine whether
|
|
> the message is warning you about an error or is giving you information.
|
|
> For example, this log message is informational:
|
|
>
|
|
> ```conf
|
|
> time="2017-06-02T15:47:37Z" level=info msg="error statting local store, serving from upstream: unknown blob" go.version=go1.7.4
|
|
> ```
|
|
>
|
|
> It's telling you that the file doesn't exist yet in the local cache and is
|
|
> being pulled from upstream.
|