the certificates in the specified location (`/etc/certs`).

2. Create a `docker-container` builder that uses this configuration:

   ```console
   $ docker buildx create --use --bootstrap \
     --name mybuilder \
     --driver docker-container \
     --config /etc/buildkitd.toml
   ```

3. Inspect the builder's configuration file (`/etc/buildkit/buildkitd.toml`), it
   shows that the certificate configuration is now configured in the builder.

   ```console
   $ docker exec -it buildx_buildkit_mybuilder0 cat /etc/buildkit/buildkitd.toml
   ```

   ```toml
   debug = true

   [registry]

     [registry."myregistry.com"]
       ca = ["/etc/buildkit/certs/myregistry.com/myregistry.pem"]

       [[registry."myregistry.com".keypair]]
         cert = "/etc/buildkit/certs/myregistry.com/myregistry_cert.pem"
         key = "/etc/buildkit/certs/myregistry.com/myregistry_key.pem"
   ```

4. Verify that the certificates are inside the container:

   ```console
   $ docker exec -it buildx_buildkit_mybuilder0 ls /etc/buildkit/certs/myregistry.com/
   myregistry.pem    myregistry_cert.pem   myregistry_key.pem
   ```

Now you can push to the registry using this builder, and it will authenticate
using the certificates:

```console
$ docker buildx build --push --tag myregistry.com/myimage:latest .
```

## CNI networking

CNI networking for builders can be useful for dealing with network port
contention during concurrent builds. CNI is [not yet](https://github.com/moby/buildkit/issues/28)
available in the default BuildKit image. But you can create your own image that
includes CNI support.

The following Dockerfile example shows a custom BuildKit image with CNI support.
It uses the [CNI config for integration tests](https://github.com/moby/buildkit/blob/master//hack/fixtures/cni.json)
in BuildKit as an example. Feel free to include your own CNI configuration.

```dockerfile
# syntax=docker/dockerfile:1

ARG BUILDKIT_VERSION=v{{% param "buildkit_version" %}}
ARG CNI_VERSION=v1.0.1

FROM --platform=$BUILDPLATFORM alpine AS cni-plugins