Add remote driver guide

Signed-off-by: Justin Chadwell <[email protected]>

docs/guides/remote-driver.md

@@ -0,0 +1,127 @@
+# Remote driver
+
+The buildx remote driver allows for more complex custom build workloads that
+allow users to connect to external buildkit instances. This is useful for
+scenarios that require manual management of the buildkit daemon, or where a
+buildkit daemon is exposed from another source.
+
+To connect to a running buildkitd instance:
+
+    $ docker buildx create \
+        --name remote \
+        --driver remote \
+        tcp://localhost:1234
+
+## Remote Buildkit over unix sockets
+
+In this scenario, we'll create a setup with buildkitd listening on a unix
+socket, and have buildx connect through it.
+
+Firstly, ensure that [buildkit](https://github.com/moby/buildkit) is installed.
+Then launch an instance of buildkitd:
+
+    $ sudo ./buildkitd --group $(id -gn) --addr unix://$HOME/buildkitd.sock
+
+This will setup a socket in your home directory that you have read-write
+permissions to. 
+
+    $ ls -lh
+    srw-rw---- 1 root user 0 May  5 11:04 /home/user/buildkitd.sock
+
+You can then connect buildx to it with the remote driver:
+
+    $ buildx create \
+        --name remote-unix \
+        --driver remote \
+        unix://$HOME/buildkitd.sock
+        
+If you list available builders, you should then see `remote-unix` among them:
+
+    $ buildx ls
+    NAME/NODE           DRIVER/ENDPOINT                        STATUS  PLATFORMS
+    test                remote
+      test0             unix:///home/.../buildkitd.sock        running linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/386
+    default *           docker
+      default           default                                running linux/amd64, linux/386
+
+We can switch to this new builder as the default using `docker buildx use remote-unix`,
+or specify it per build:
+
+    $ docker buildx build --builder=remote-unix -t test --load .
+
+(remember that `--load` is neccessary when not using the default `docker`
+driver, to load the build result into the docker daemon)
+
+## Remote Buildkit in Docker container
+
+In this scenario, we'll create a similar setup to the `docker-container`
+driver, by manually booting a buildkit docker container and connecting to it
+using the buildx remote driver. In most cases you'd probably just use the
+`docker-container` driver directly, but imagine that for some reason you want
+to manually manage the container instead of having buildx manage it for you.
+
+First, we need to generate certificates for buildkit - you can use the 
+[create-certs.sh](https://github.com/moby/buildkit/blob/master/examples/kubernetes/create-certs.sh)
+script as a starting point. Note, that while it is *possible* to expose
+buildkit over TCP without using TLS, it is **not recommened**, since this will
+allow arbitrary access to buildkit without credentials.
+
+With our certificates generated in `.certs/`, we startup the container:
+
+    $ docker run -d --rm \
+        --name=remote-buildkitd \
+        --privileged \
+        -p 1234:1234 \
+        -v $PWD/.certs:/certs \
+        moby/buildkit:latest \
+        --addr tcp://0.0.0.0:1234 \
+        --tlscacert /certs/ca.pem \
+        --tlscert /certs/daemon-cert.pem \
+        --tlskey /certs/daemon-key.pem
+
+The above command starts a buildkit container and exposes the daemon's port
+1234 to localhost.
+
+We can now connect to this running container using buildx:
+
+    $ docker buildx create \
+        --name remote-kubernetes \
+        --driver remote \
+        --driver-opt cacert=.certs/ca.pem,cert=.certs/client-cert.pem,key=.certs/client-key.pem,servername=... \
+        tcp://buildkitd.default.svc:1234
+
+# Remote Buildkit in Kubernetes
+
+In this scenario, we'll create a similar setup to the `kubernetes` driver by
+manually creating a buildkit `Deployment`. While the `kubernetes` driver will
+do this under-the-hood, it might sometimes be desirable to scale buildkit
+manually. Additionally, when executing builds from inside Kubernetes pods,
+the buildx builder will need to be recreated from within each pod or copied
+between them.
+
+Firstly, we can create a kubernetes deployment of buildkitd, as per the
+instructions [here](https://github.com/moby/buildkit/tree/master/examples/kubernetes).
+Following the guide, we setup certificates for the buildkit daemon and client
+(as above using [create-certs.sh](https://github.com/moby/buildkit/blob/master/examples/kubernetes/create-certs.sh))
+and create a `Deployment` of buildkit pods with a service that connects to
+them.
+
+Assuming that the service is called `buildkitd`, we can create a remote builder
+in buildx, ensuring that the listed certificate files are present:
+
+    $ docker buildx create \
+        --name remote-kubernetes \
+        --driver remote \
+        --driver-opt cacert=.certs/ca.pem,cert=.certs/client-cert.pem,key=.certs/client-key.pem \
+        tcp://buildkitd.default.svc:1234
+
+Note that the above will only work in-cluster (since the buildkit setup guide
+only creates a ClusterIP service). To configure the builder to be accessible
+remotely, you can use an appropriately configured Ingress, which is outside the
+scope of this guide.
+
+Alternatively, to access remotely use the port forwarding mechanism in kubectl:
+
+    $ kubectl port-forward svc/buildkitd 1234:1234
+
+Then you can simply point the remote driver at `tcp://localhost:1234`.