repo sync

content/actions/hosting-your-own-runners/monitoring-and-troubleshooting-self-hosted-runners.md

@@ -11,6 +11,7 @@ versions:
   ghae: '*'
   ghec: '*'
 type: tutorial
+miniTocMaxHeadingLevel: 3
 defaultPlatform: linux
 shortTitle: Monitor & troubleshoot
 ---
@@ -265,3 +266,20 @@ User=runner-user
 
 If your runners are offline for this reason, manually update the runners. For more information, see the installation instructions for [the latest release](https://github.com/actions/runner/releases/latest) in the actions/runner repository.
 {% endif %}
+
+### Checking which Docker engine is installed on the runner
+
+If your build fails with the following error:
+
+```shell
+Error: Input required and not supplied: java-version
+```
+
+Check which Docker engine is installed on your self-hosted runner. To pass the inputs of an action into the Docker container, the runner uses environment variables that might contain dashes as part of their names. The action may not able to get the inputs if the Docker engine is not a binary executable, but is instead a shell wrapper or a link (for example, a Docker engine installed on Linux using `snap`). To address this error, configure your self-hosted runner to use a different Docker engine. 
+
+To check if your Docker engine was installed using `snap`, use the `which` command. In the following example, the Docker engine was installed using `snap`:
+
+```shell
+$ which docker
+/snap/bin/docker
+```