I am trying to enable non-TLS access to Docker remote API, so I could use Postman REST client running on Windows and hit docker API running on docker-machine in the VirtualBox. Running latest Docker Toolbox, using latest Oracle VirtualBox, with Windows 7 as a host OS. Starting in 18.09+, the dind variants of this image. This is from Docker's official documentation. One of the features affects GitLab CI/CD when using the Docker in Docker workflow.As of version 19.03, docker:dind will automatically generate TLS certificates and require using them for communication. Last week Docker released a new version, 19.03, which brings a few exciting features with it.But I think if user don't set server credential, it should disable tls verify option regardless of jenkins global env variable. I found it out that if there is Env variable named 'DOCKER_TLS_VERIFY' in jenkins global configuration, then this plugin use tls.
