diff --git a/docs/os/configuration/docker/index.md b/docs/os/configuration/docker/index.md
index 93681fa2..087de7d9 100644
--- a/docs/os/configuration/docker/index.md
+++ b/docs/os/configuration/docker/index.md
@@ -28,7 +28,7 @@ You can also customize Docker after it's been started using `ros config`.
 $ sudo ros config set rancher.docker.storage_driver overlay
 ```
 
-#### Valid Keys for Docker
+#### User Docker settings
 
 Many of the standard Docker daemon arguments can be placed under the `rancher.docker` key. The command needed to start the Docker daemon will be generated based on these arguments. The following arguments are currently supported.
 
@@ -77,7 +77,7 @@ rancher:
     storage_driver: overlay
 ```
 
-#### Valid Keys for System Docker
+#### System Docker settings
 
 All daemon arguments shown in the first table are also available to System Docker. The following are also supported.
 
@@ -85,3 +85,40 @@ Key | Value | Default | Description
 ---|---|---| ---
 `extra_args` | List of Strings | `[]` | Arbitrary daemon arguments, appended to the generated command
 `environment` | List of Strings (optional) | `[]` |
+
+### Using a pull through registry mirror
+
+There are 3 Docker engines that can be configured to use the pull-through Docker Hub registry mirror cache:
+
+```
+#cloud-config
+rancher:
+  bootstrap_docker:
+    registry_mirror: "http://10.10.10.23:5555"
+  docker:
+    registry_mirror: "http://10.10.10.23:5555"
+  system_docker:
+    registry_mirror: "http://10.10.10.23:5555"
+```
+
+`bootstrap_docker` is used to prepare and initial network and pull any cloud-config options that can be used to configure the final network configuration and System-docker - its very unlikely to pull any images.
+
+A successful pull through mirror cache request by System-docker looks like:
+
+```
+[root@rancher-dev rancher]# system-docker pull alpine
+Using default tag: latest
+DEBU[0201] Calling GET /v1.23/info
+> WARN[0201] Could not get operating system name: Error opening /usr/lib/os-release: open /usr/lib/os-release: no such file or directory
+WARN[0201] Could not get operating system name: Error opening /usr/lib/os-release: open /usr/lib/os-release: no such file or directory
+DEBU[0201] Calling POST /v1.23/images/create?fromImage=alpine%3Alatest
+DEBU[0201] hostDir: /etc/docker/certs.d/10.10.10.23:5555
+DEBU[0201] Trying to pull alpine from http://10.10.10.23:5555/ v2
+DEBU[0204] Pulling ref from V2 registry: alpine:latest
+DEBU[0204] pulling blob "sha256:2aecc7e1714b6fad58d13aedb0639011b37b86f743ba7b6a52d82bd03014b78e" latest: Pulling from library/alpine
+DEBU[0204] Downloaded 2aecc7e1714b to tempfile /var/lib/system-docker/tmp/GetImageBlob281102233 2aecc7e1714b: Extracting  1.99 MB/1.99 MB
+DEBU[0204] Untar time: 0.161064213s
+DEBU[0204] Applied tar sha256:3fb66f713c9fa9debcdaa58bb9858bd04c17350d9614b7a250ec0ee527319e59 to 841c99a5995007d7a66b922be9bafdd38f8090af17295b4a44436ef433a2aecc7e1714b: Pull complete
+Digest: sha256:0b94d1d1b5eb130dd0253374552445b39470653fb1a1ec2d81490948876e462c
+Status: Downloaded newer image for alpine:latest
+```