Using the Fly Docker registry

Author: simonw

fly/fly-docker-registry.md

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+# Using the Fly Docker registry
+
+[Fly.io](https://fly.io/) lets you deploy Docker containers that will be compiled as a Firecracker VM and run in locations around the world.
+
+Fly offer [a number of ways](https://fly.io/docs/reference/builders/) to build and deploy apps. For many frameworks you can run `fly launch` and it will detect the framework and configure a container for you. For others you can pass it a `Dockerfile` which will be built and deployed. But you can also push your own images to a Docker registry and deploy them to Fly.
+
+Today I figured out how to use Fly's own registry to deploy an app.
+
+## Tagging images for the Fly registry
+
+Fly's registry is called `registry.fly.io`. To use it, you need to tag your Docker images with a tag that begins with that string.
+
+Every Fly app gets its own registry subdomain. You can create apps in a number of ways, but the easiest is to use the Fly CLI:
+
+    flyctl apps create datasette-demo
+
+Fly app names must be globally unique across all of Fly - you will get an error if the app name is already taken.
+
+You can create an app with a random, freely available name using the `--generate-name` option:
+
+```
+~ % flyctl apps create --generate-name
+? Select Organization: Simon Willison (personal)
+New app created: rough-dew-1296
+```
+
+Now that you have an app name, you can tag your Docker image using:
+
+    registry.fly.io/your-app-name:unique-tag-for-your-image
+
+If you are building an image using Docker on your machine, you can run this command in the same directory as your `Dockerfile`:
+
+    docker build -t registry.fly.io/datasette-demo:datasette-demo-v0 .
+
+## Pushing images to the registry
+
+In order to push your image to Fly, you will first need to [authenticate](https://fly.io/docs/flyctl/auth-docker/).
+
+The `flyctl auth docker` command will do this for you:
+```
+~ % flyctl auth docker
+Authentication successful. You can now tag and push images to registry.fly.io/{your-app}
+```
+This works by hooking into Docker's own authentication mechanism. You can see what it has done by looking at your `~/.docker/config.json` file. Mine looks like this:
+
+```json
+{
+  "auths": {
+    "registry.fly.io": {
+      "auth": "... secret token here ..."
+    }
+  ,
+  "experimental": "disabled",
+  "stackOrchestrator": "swarm"
+}
+```
+Now you can push your image to the registry like this:
+
+    docker push registry.fly.io/datasette-demo:datasette-demo-v0
+
+## Deploying an image
+
+Now that your image is pushed, you can deploy an instance of it like this:
+
+    flyctl deploy --app datasette-demo \
+      --image registry.fly.io/datasette-demo:datasette-demo-v0
+
+A few seconds later your app will be running at:
+
+    https://name-of-your-app.fly.dev/