In Docker versions prior to 18.09, containerd was managed by the Docker engine daemon. In Docker Engine 18.09, containerd is managed by systemd. Since containerd is managed by systemd, any custom configuration to the `docker.service` systemd
configuration which changes mount settings (for example, `MountFlags=slave`) breaks interactions between the Docker Engine daemon and containerd, and you will not be able to start containers.
Run the following command to get the current value of the `MountFlags` property for the `docker.service`:
```console
$ sudo systemctl show --property=MountFlags docker.service
MountFlags=
```
Update your configuration if this command prints a non-empty value for `MountFlags`, and restart the docker service.
### New features
* Updated API version to 1.39 [moby/moby#37640](https://github.com/moby/moby/pull/37640)
* Added support for remote connections using SSH [docker/cli#1014](https://github.com/docker/cli/pull/1014)
* Builder: added prune options to the API [moby/moby#37651](https://github.com/moby/moby/pull/37651)
* Added "Warnings" to `/info` endpoint, and move detection to the daemon [moby/moby#37502](https://github.com/moby/moby/pull/37502)
* Allows BuildKit builds to run without experimental mode enabled. Buildkit can now be configured with an option in daemon.json [moby/moby#37593](https://github.com/moby/moby/pull/37593) [moby/moby#37686](https://github.com/moby/moby/pull/37686) [moby/moby#37692](https://github.com/moby/moby/pull/37692) [docker/cli#1303](https://github.com/docker/cli/pull/1303) [docker/cli#1275](https://github.com/docker/cli/pull/1275)
* Added support for build-time secrets using a `--secret` flag when using BuildKit [docker/cli#1288](https://github.com/docker/cli/pull/1288)
* Added SSH agent socket forwarder (`docker build --ssh $SSHMOUNTID=$SSH_AUTH_SOCK`) when using BuildKit [docker/cli#1438](https://github.com/docker/cli/pull/1438) / [docker/cli#1419](https://github.com/docker/cli/pull/1419)
* Added `--chown` flag support for `ADD` and `COPY` commands on Windows [moby/moby#35521](https://github.com/moby/moby/pull/35521)
* Added `builder prune` subcommand to prune BuildKit build cache [docker/cli#1295](https://github.com/docker/cli/pull/1295) [docker/cli#1334](https://github.com/docker/cli/pull/1334)
* BuildKit: Adds configurable garbage collection policy for the BuildKit build cache [docker/engine#59](https://github.com/docker/engine/pull/59) / [moby/moby#37846](https://github.com/moby/moby/pull/37846)
* BuildKit: Adds support for `docker build --pull ...` when using BuildKit [moby/moby#37613](https://github.com/moby/moby/pull/37613)
* BuildKit: Adds support or "registry-mirrors" and "insecure-registries" when using BuildKit [docker/engine#59](https://github.com/docker/engine/pull/59) / [moby/moby#37852](https://github.com/moby/moby/pull/37852)
* BuildKit: Enables net modes and bridge. [moby/moby#37620](https://github.com/moby/moby/pull/37620)
* Added `docker engine` subcommand to manage the lifecycle of a Docker Engine running as a privileged container on top of containerd, and to allow upgrades to Docker Engine Enterprise [docker/cli#1260](https://github.com/docker/cli/pull/1260)
* Exposed product license in `docker info` output [docker/cli#1313](https://github.com/docker/cli/pull/1313)
* Showed warnings produced by daemon in `docker info` output [docker/cli#1225](https://github.com/docker/cli/pull/1225)
* Added "local" log driver [moby/moby#37092](https://github.com/moby/moby/pull/37092)
* Amazon CloudWatch: adds `awslogs-endpoint` logging option [moby/moby#37374](https://github.com/moby/moby/pull/37374)
* Added support for global default address pools [moby/moby#37558](https://github.com/moby/moby/pull/37558) [docker/cli#1233](https://github.com/docker/cli/pull/1233)
* Configured containerd log-level to be the same as dockerd [moby/moby#37419](https://github.com/moby/moby/pull/37419)
* Added configuration option for cri-containerd [moby/moby#37519](https://github.com/moby/moby/pull/37519)