+
+h2. Troubleshooting
+
+h3. Workflows fail with @ValidationException: Not found: '/var/lib/cwl/workflow.json#main'@
+
+A possible configuration error is having Docker installed as a @snap@ package rather than a @deb@ package. This is a problem because @snap@ packages are partially containerized and may have a different view of the filesystem than @crunch-run@. This will produce confusing problems, for example, directory bind mounts sent to Docker that are empty (instead of containing the intended files) and resulting in unexpected "file not found" errors.
+
+To check for this situation, run @snap list@ and look for @docker@. If found, run @snap remove docker@ and follow the instructions to above to "install Docker Engine":#install_docker .