docker quickstart: mention tunnel + troubleshooting (#4653)

docs/quickstart/docker.md

@@ -17,18 +17,26 @@ Coder with Docker has the following advantages:
 
     The Coder server binds to port 3000 by default. Use `--address :<port>` to customize it!
 
+    Use the [Coder tunnel](../admin/configure.md#tunnel) for a public URL:
+
     ```bash
-    $ coder server
+    coder server
     ```
 
-1.  Run `coder login http://localhost:3000` in a new terminal and follow the
+    Or set an [access URL](../admin/configure.md#access-url) to run entirely locally:
+
+    ```bash
+    coder server --access-url=http://localhost:3000 --address=:3000
+    ```
+
+1.  Run `coder login <access url>` in a new terminal and follow the
     interactive instructions to create your user.
 
 1.  Pull the "Docker" example template using the interactive `coder templates init`:
 
     ```bash
-    $ coder templates init
-    $ cd docker
+    coder templates init
+    cd docker
     ```
 
 1.  Push up the template with `coder templates create`
@@ -53,6 +61,16 @@ Coder with Docker has the following advantages:
 1.  If you want to modify the Docker image or template, edit the files in the
     previously created `./docker` directory, then run `coder templates push`.
 
+## Troubleshooting
+
+### Docker-based workspace is stuck in "Connecting..."
+
+Ensure you have an externally-reachable `CODER_ACCESS_URL` set. See [troubleshooting templates](../templates.md#creating-and-troubleshooting-templates) for more steps.
+
+### Permission denied while trying to connect to the Docker daemon socket
+
+See Docker's official documentation to [Manage Docker as a non-root user](https://docs.docker.com/engine/install/linux-postinstall/#manage-docker-as-a-non-root-user).
+
 ## Next Steps
 
 - [Port-forward](../networking/port-forwarding.md)