Correct the quotations in the command to add the -r=false flag. Thanks to @tianon for pointing this out.

docs/sources/use/host_integration.rst

@@ -54,7 +54,7 @@ Run the following command:
 
 .. code-block:: bash
 
-   $ sudo sh -c 'echo DOCKER_OPTS="-r=false" > /etc/default/docker'
+   $ sudo sh -c "echo DOCKER_OPTS=\"-r=false\" > /etc/default/docker"
 
 
 Sample systemd Script