Merge "Document the China registry mirror"

doc/source/user/troubleshooting.rst

@@ -10,6 +10,24 @@ Failures
 If Kolla fails, often it is caused by a CTRL-C during the deployment
 process or a problem in the ``globals.yml`` configuration.
 
+.. note::
+
+   In some countries like China, Kolla might fail due to unable to pull images
+   from `Docker Hub <https://hub.docker.com/u/kolla/>`__. There is a workround
+   to solve this issue:
+
+   .. code-block:: console
+
+      mkdir -p /etc/docker
+      tee /etc/docker/daemon.json <<-'EOF'
+      {
+        "registry-mirrors": ["https://registry.docker-cn.com"]
+      }
+      EOF
+      systemctl restart docker
+
+   .. end
+
 To correct the problem where Operators have a misconfigured environment,
 the Kolla community has added a precheck feature which ensures the
 deployment targets are in a state where Kolla may deploy to them. To