`--fixed-cidr-v6` option, the Docker daemon will refuse to start with the
following message:
```none
Error starting daemon: Error initializing network controller: Error creating
default "bridge" network: failed to parse pool request
for address space "LocalDefault" pool " subpool ":
could not find an available, non-overlapping IPv6 address
pool among the defaults to assign to the network
```
To resolve this error, either remove the `--ipv6` flag (to preserve the same
behavior as in Docker 1.12.3 and earlier), or provide an IPv6 subnet as the
value of the `--fixed-cidr-v6` flag.
In a similar way, if you specify the `--ipv6` flag when creating a network
with the default IPAM driver, without providing an IPv6 `--subnet`, network
creation will fail with the following message:
```none
Error response from daemon: failed to parse pool request for address space
"LocalDefault" pool "" subpool "": could not find an
available, non-overlapping IPv6 address pool among
the defaults to assign to the network
```
To resolve this, either remove the `--ipv6` flag (to preserve the same behavior
as in Docker 1.12.3 and earlier), or provide an IPv6 subnet as the value of the
`--subnet` flag.
The network network creation will instead succeed if you use an external IPAM driver
which supports automatic allocation of IPv6 subnets.
### Runtime
- Fix race on sending stdin close event [#29424](https://github.com/docker/docker/pull/29424)
### Networking
- Fix panic in docker network ls when a network was created with `--ipv6` and no ipv6 `--subnet` in older docker versions [#29416](https://github.com/docker/docker/pull/29416)
### Contrib
- Fix compilation on Darwin [#29370](https://github.com/docker/docker/pull/29370)
## 1.12.4 (2016-12-12)
> [!IMPORTANT]
>
> Docker 1.12 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.
### Runtime
- Fix issue where volume metadata was not removed [#29083](https://github.com/docker/docker/pull/29083)
- Asynchronously close streams to prevent holding container lock [#29050](https://github.com/docker/docker/pull/29050)
- Fix selinux labels for newly created container volumes [#29050](https://github.com/docker/docker/pull/29050)
- Remove hostname validation [#28990](https://github.com/docker/docker/pull/28990)
- Fix deadlocks caused by IO races [#29095](https://github.com/docker/docker/pull/29095) [#29141](https://github.com/docker/docker/pull/29141)
- Return an empty stats if the container is restarting [#29150](https://github.com/docker/docker/pull/29150)
- Fix volume store locking [#29151](https://github.com/docker/docker/pull/29151)