- Fix connection leak when a node leaves a swarm [swarmkit/#1277](https://github.com/docker/swarmkit/pull/1277)
- Backdate swarm certificates by one hour to tolerate more clock skew [swarmkit/#1243](https://github.com/docker/swarmkit/pull/1243)
- Avoid high CPU use with many unschedulable tasks [swarmkit/#1287](https://github.com/docker/swarmkit/pull/1287)
- Fix issue with global tasks not starting up [swarmkit/#1295](https://github.com/docker/swarmkit/pull/1295)
- Garbage collect raft logs [swarmkit/#1327](https://github.com/docker/swarmkit/pull/1327)
### Volume
- Persist local volume options after a daemon restart [#25316](https://github.com/docker/docker/pull/25316)
- Fix an issue where the mount ID was not returned on volume unmount [#25333](https://github.com/docker/docker/pull/25333)
- Fix an issue where a volume mount could inadvertently create a bind mount [#25309](https://github.com/docker/docker/pull/25309)
- `docker service create --mount type=bind,...` now correctly validates if the source path exists, instead of creating it [#25494](https://github.com/docker/docker/pull/25494)
## 1.12.0 (2016-07-28)
> [!IMPORTANT]
>
> Docker 1.12.0 ships with an updated systemd unit file for rpm
based installs (which includes RHEL, Fedora, CentOS, and Oracle Linux 7). When upgrading from an older version of Docker, the upgrade process may not automatically install the updated version of the unit file, or fail to start the `docker service` if;
> - the systemd unit file (`/usr/lib/systemd/system/docker.service`) contains local changes, or
> - a systemd drop-in file is present, and contains `-H fd://` in the `ExecStart` directive
Starting the `docker service` will produce an error:
Failed to start docker.service: Unit docker.socket failed to load: No such file or directory.
or
no sockets found via socket activation: make sure the service was started by systemd.
To resolve this:
- Backup the current version of the unit file, and replace the file with the
[version that ships with docker 1.12](https://raw.githubusercontent.com/docker/docker/v1.12.0/contrib/init/systemd/docker.service.rpm)
- Remove the `Requires=docker.socket` directive from the `/usr/lib/systemd/system/docker.service` file if present
- Remove `-H fd://` from the `ExecStart` directive (both in the main unit file, and in any drop-in files present).
After making those changes, run `sudo systemctl daemon-reload`, and `sudo
systemctl restart docker` to reload changes and (re)start the docker daemon.
> [!IMPORTANT]
>
> With Docker 1.12, a Linux `docker` installation now has two
additional binaries; `dockerd`, and `docker-proxy`. If you have scripts for installing `docker`, make sure to update them accordingly.
### Builder
+ New `HEALTHCHECK` Dockerfile instruction to support user-defined healthchecks [#23218](https://github.com/docker/docker/pull/23218)
+ New `SHELL` Dockerfile instruction to specify the default shell when using the shell form for commands in a Dockerfile [#22489](https://github.com/docker/docker/pull/22489)
+ Add `#escape=` Dockerfile directive to support platform-specific parsing of file paths in Dockerfile [#22268](https://github.com/docker/docker/pull/22268)
+ Add support for comments in `.dockerignore` [#23111](https://github.com/docker/docker/pull/23111)
* Support for UTF-8 in Dockerfiles [#23372](https://github.com/docker/docker/pull/23372)
* Skip UTF-8 BOM bytes from `Dockerfile` and `.dockerignore` if exist [#23234](https://github.com/docker/docker/pull/23234)
* Windows: support for `ARG` to match Linux [#22508](https://github.com/docker/docker/pull/22508)
- Fix error message when building using a daemon with the bridge network disabled [#22932](https://github.com/docker/docker/pull/22932)
### Contrib
* Enable seccomp for Centos 7 and Oracle Linux 7 [#22344](https://github.com/docker/docker/pull/22344)
- Remove MountFlags in systemd unit to allow shared mount propagation [#22806](https://github.com/docker/docker/pull/22806)