Add a doc to explain Clear Containers support in Zun

Change-Id: I9ac92c003b2d7fe063f0fe2c7673d9ac8b31de3b

doc/source/admin/clear-containers.rst

@@ -0,0 +1,36 @@
+=======================
+Clear Containers in Zun
+=======================
+
+Zun now supports running Clear Containers with regular Docker containers.
+Clear containers run containers as very lightweight virtual machines
+which boots up really fast and has low memory footprints. It provides
+security to the containers with an isolated environment. You can read
+more about Clear Containers `here <https://github.com/clearcontainers/runtime/wiki>`_.
+
+Installation with DevStack
+==========================
+It is possible to run Clear Containers with Zun. Follow the
+:doc:`/contributor/quickstart` to download DevStack, Zun code and copy the
+local.conf file. Now perform the following steps to install Clear Containers
+with DevStack::
+
+    cd /opt/stack/devstack
+    echo "ENABLE_CLEAR_CONTAINER=true" >> local.conf
+    ./stack.sh
+
+Verify the installation by::
+
+    $ sudo docker info | grep Runtimes
+    Runtimes: cor runc
+
+Using Clear Containers with Zun
+===============================
+To create Clear Containers with Zun, specify the `--runtime` option::
+
+    zun run --name clear-container --runtime cor cirros ping -c 4 8.8.8.8
+
+.. note::
+
+    Clear Containers support in Zun is not production ready. It is recommended
+    not to run Clear Containers and runc containers on the same host.

doc/source/admin/index.rst

@@ -12,3 +12,4 @@ the services.
   :maxdepth: 1
 
   osprofiler
+  clear-containers