Merge branch 'master' into rrl-wip

1 files changed, 54 insertions, 7 deletions

diff --git a/doc/user/deployment-docker.rst b/doc/user/deployment-docker.rst
index 462ab061..42f5503b 100644
--- a/doc/user/deployment-docker.rst
+++ b/doc/user/deployment-docker.rst
@@ -2,20 +2,67 @@
 Docker
 ******
 
-
 .. note::
 
-    Before version 6, our Docker images were not meant to be used in production. This is no longer the case and with the introduction of ``kres-manager``, Knot Resolver runs in containers without any issues.
+    Before version 6, our Docker images were not intended for production use due to the lack of ``systemd`` in Docker and
+    the inability to manage the multiple independent parts of the resolver.
+    This is no longer the case since the introduction of the Manager that automatically control other parts of the resolver.
+
+Knot Resolver official Docker image can be found at `Docker Hub <https://hub.docker.com/r/cznic/knot-resolver>`_.
+First you can try running the container in interactive mode.
+
+.. code-block:: bash
+
+    $ docker run --rm -ti --network host docker.io/cznic/knot-resolver:6
 
-An official Docker image can be found on `Docker Hub <https://hub.docker.com/r/cznic/knot-resolver>`_. The image contains Knot Resolver as if it was installed from our official distro packages.
+For more robust deployments you will also probably need to configure network, for that see `Docker networking <https://docs.docker.com/engine/network/>`_.
+
+Now you can try sending a query to the resolver using `kdig <https://www.knot-dns.cz/docs/latest/html/man_kdig.html>`_.
 
 .. code-block:: bash
 
-    docker run --rm -ti -P docker.io/cznic/knot-resolver
+    $ kdig example.com @127.0.0.1
+    $ kdig nic.cz @127.0.0.1#443 +https
 
-The configuration file is located at ``/etc/knot-resolver/config.yaml`` and the cache is at ``/var/cache/knot-resolver``. We recommend configuring a persistent cache across container restarts.
+The image contains full Knot Resolver installation, so there shouldn't be much difference between running it natively and running it in a container.
+The configuration file is located at ``/etc/knot-resolver/config.yaml`` and the cache is at ``/var/cache/knot-resolver``.
+Please do not change these and other paths (rundir) as you may break things inside the container.
 
 .. warning::
     
-    While the container image contains normal installation of Knot Resolver and there shouldn't be any differences between running it natively and in a container, we (the developers) do not have any experience using the Docker image in production. Especially, beware of running the DNS resolver with a software defined network (i.e. in Kubernetes). There will likely be some performance penalties for doing so. We haven't done any measurements comparing different types of installations so we don't know the performance differences. If you have done some measurements yourself, please reach out to us and we will share it here with everyone else.
-    
\ No newline at end of file
+    Beware of running the container with a software defined network (i.e. in Kubernetes).
+    This will likely to result in some performance losses.
+    We haven't done any measurements comparing different types of installations so we don't know the performance differences.
+    If you have done your own measurements yourself, please contact us and we will share it with everyone else.
+
+------
+Config
+------
+
+We recommend persistent configuration across container restarts,
+for more see `Docker persisting container data <https://docs.docker.com/get-started/docker-concepts/running-containers/persisting-container-data/>`_.
+
+.. code-block:: bash
+
+    $ docker volume create config
+    $ docker run --rm -ti --network host -v config:/etc/knot-resolver docker.io/cznic/knot-resolver:6
+
+After a configuration change there is no need to restart the entire container, just tell the resolver to reload the configuration.
+Get ``CONTAINER_ID`` using the ``docker ps`` command or give your container name with the ``--name`` argument at container startup.
+
+.. code-block:: bash
+
+    $ docker exec -it CONTANER_ID kresctl reload
+
+-----
+Cache
+-----
+
+You can also use persistent volume for the cache, but sharing it between more containers requires special option ``--pid=host``.
+This is caused by the LMDB's reliance on unique PID numbers, see `issue #637 <https://gitlab.nic.cz/knot/knot-resolver/-/issues/637>`_ for more information.
+It is also good to mount the cache on ``tmpfs`` (semi-persistent), otherwise it will not work well under heavy load.
+
+.. code-block:: bash
+
+    $ docker volume create --opt type=tmpfs --opt device=tmpfs cache
+    $ docker run --rm -ti --pid=host --network host -v cache:/var/cache/knot-resolver docker.io/cznic/knot-resolver:6