2014-07-18 14:48:19 -04:00
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page_title: Run a local registry mirror
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page_description: How to set up and run a local registry mirror
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page_keywords: docker, registry, mirror, examples
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# Run a local registry mirror
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## Why?
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If you have multiple instances of Docker running in your environment
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(e.g., multiple physical or virtual machines, all running the Docker
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daemon), each time one of them requires an image that it doesn't have
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it will go out to the internet and fetch it from the public Docker
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registry. By running a local registry mirror, you can keep most of the
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image fetch traffic on your local network.
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## How does it work?
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The first time you request an image from your local registry mirror,
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it pulls the image from the public Docker registry and stores it locally
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before handing it back to you. On subsequent requests, the local registry
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mirror is able to serve the image from its own storage.
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## How do I set up a local registry mirror?
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There are two steps to set up and use a local registry mirror.
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### Step 1: Configure your Docker daemons to use the local registry mirror
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You will need to pass the `--registry-mirror` option to your Docker daemon on
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startup:
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2014-11-16 01:40:48 -05:00
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sudo docker --registry-mirror=http://<my-docker-mirror-host> -d
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2014-07-18 14:48:19 -04:00
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For example, if your mirror is serving on `http://10.0.0.2:5000`, you would run:
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2014-11-16 01:40:48 -05:00
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sudo docker --registry-mirror=http://10.0.0.2:5000 -d
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2014-07-18 14:48:19 -04:00
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**NOTE:**
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Depending on your local host setup, you may be able to add the
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`--registry-mirror` options to the `DOCKER_OPTS` variable in
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`/etc/defaults/docker`.
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### Step 2: Run the local registry mirror
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You will need to start a local registry mirror service. The
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[`registry` image](https://registry.hub.docker.com/_/registry/) provides this
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functionality. For example, to run a local registry mirror that serves on
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port `5000` and mirrors the content at `registry-1.docker.io`:
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2014-11-16 01:40:48 -05:00
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sudo docker run -p 5000:5000 \
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2014-07-18 14:48:19 -04:00
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-e STANDALONE=false \
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-e MIRROR_SOURCE=https://registry-1.docker.io \
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-e MIRROR_SOURCE_INDEX=https://index.docker.io registry
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## Test it out
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With your mirror running, pull an image that you haven't pulled before (using
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`time` to time it):
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2014-11-16 01:40:48 -05:00
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$ time sudo docker pull node:latest
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2014-07-18 14:48:19 -04:00
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Pulling repository node
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[...]
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real 1m14.078s
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user 0m0.176s
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sys 0m0.120s
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Now, remove the image from your local machine:
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2014-09-15 21:49:05 -04:00
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$ sudo docker rmi node:latest
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2014-07-18 14:48:19 -04:00
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Finally, re-pull the image:
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2014-11-16 01:40:48 -05:00
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$ time sudo docker pull node:latest
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2014-07-18 14:48:19 -04:00
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Pulling repository node
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[...]
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real 0m51.376s
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user 0m0.120s
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sys 0m0.116s
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The second time around, the local registry mirror served the image from storage,
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avoiding a trip out to the internet to refetch it.
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