Docker 1.9.0 RC4 发布，包含众多改进内容：

Runtime

docker stats now returns block IO metrics (#15005)
docker stats now details network stats per interface (#15786)
Add ancestor=<image> filter to docker ps --filter flag to filter containers based on their ancestor images (#14570)
Add label=<somelabel> filter to docker ps --filter to filter containers based on label (#16530)
Add --kernel-memory flag to docker run (#14006)
Add --message flag to docker import allowing to specify an optional message (#15711)
Add --privileged flag to docker exec (#14113)
Add --stop-signal flag to docker run allowing to replace the container process stopping signal (#15307)
Add a new unless-stopped restart policy (#15348)
Inspecting an image now returns tags (#13185)
Add container size information to docker inspect (#15796)
Add RepoTags and RepoDigests field to /images/{name:.*}/json (#17275)
Remove the deprecated /container/ps endpoint from the API (#15972)
Send and document correct HTTP codes for /exec/<name>/start (#16250)
Share shm and mqueue between containers sharing IPC namespace (#15862)
Event stream now shows OOM status when --oom-kill-disable is set (#16235)
Ensure special network files (/etc/hosts etc.) are read-only if bind-mounted with ro option (#14965)
Improve rmi performance (#16890)
Do not update /etc/hosts for the default bridge network, except for links (#17325)
Fix conflict with duplicate container names (#17389)
Fix an issue with incorrect template execution in docker inspect (#17284)
DEPRECATE -c short flag variant for --cpu-shares in docker run (#16271)

Client

Allow docker import to import from local files (#11907)

Builder

Add a STOPSIGNAL Dockerfile instruction allowing to set a different stop-signal for the container process (#15307)
Add an ARG Dockerfile instruction and a --build-arg flag to docker build that allows to add build-time environment variables (#15182)
Improve cache miss performance (#16890)

Storage

devicemapper: Implement deferred deletion capability (#16381)

Networking

docker network exits experimental and is part of standard release (#16645)
New network top-level concept, with associated subcommands and API (#16645)
Support for multiple isolated/micro-segmented networks (#16645)
Built-in multihost networking using VXLAN based overlay driver (#14071)
Support for third-party network plugins (#13424)
Ability to dynamically connect containers to multiple networks (#16645)
Support for user-defined IP address management via pluggable IPAM drivers (#16910)
Add daemon flags --cluster-store and --cluster-advertise for built-in nodes discovery (#16229)
Add --cluster-store-opt for setting up TLS settings (#16644)
Add --dns-opt to the daemon (#16031)
DEPRECATE following container NetworkSettings fields in API v1.21: EndpointID,Gateway,GlobalIPv6Address, GlobalIPv6PrefixLen, IPAddress, IPPrefixLen,IPv6Gateway and MacAddress. Those are now specific to the bridge network. UseNetworkSettings.Networks to inspect the networking settings of a container per network.

Volumes

New top-level volume subcommand and API (#14242)
Move API volume driver settings to host-specific config (#15798)
Print an error message if volume name is not unique (#16009)
Ensure volumes created from Dockerfiles always use the local volume driver (#15507)
DEPRECATE auto-creating missing host paths for bind mounts (#16349)

Logging

Add awslogs logging driver for Amazon CloudWatch (#15495)
Add generic tag log option to allow customizing container/image information passed to driver (e.g. show container names) (#15384)
Implement the docker logs endpoint for the journald driver (#13707)
DEPRECATE driver-specific log tags (e.g. syslog-tag, etc.) (#15384)

Distribution

docker search now works with partial names (#16509)
Push optimization: avoid buffering to file (#15493)
The daemon will display progress for images that were already being pulled by another client (#15489)
Only permissions required for the current action being performed are requested (#)
Renaming trust keys (and respective environment variables) from offline to root andtagging to repository (#16894)
DEPRECATE trust key environment variables DOCKER_CONTENT_TRUST_OFFLINE_PASSPHRASE andDOCKER_CONTENT_TRUST_TAGGING_PASSPHRASE (#16894)