Rocket 0.9.0 发布 CoreOS 的容器引擎

rkt v0.9.0 发布，此版本值得关注的改进：

The on-disk format for pod trees has changed slightly, meaning thatrkt gc and rkt run-prepared may not work for pods created by previous versions of rkt. To work around this, we recommend removing the pods with an older version of rkt.
The --private-net flag has been renamed to --net and its semantic has changed (in particular, it is now enabled by default) – see below for details.
Several changes to CLI output (e.g. column names) from the rkt list andrkt image list subcommands.
The image fetching behaviour has changed, with the introduction of new flags to rkt runand rkt fetch and the removal of --local – see below for details.

新特性和 UX 改进

--private-net –> --net, and networking is now private by default
New image fetching behaviour
Unprivileged users
/etc/hosts 支持

其他新特性

rkt now supports setting supplementary group IDs on processes (#1514).
rkt’s use of cgroups has been reworked to facilitate rkt running on a variety of operating systems like Void and older non-systemd distributions (#1437, #1320, #1076, #1042)
If rkt run is used with an image that does not have an app section, rkt will now create one if the user provides an --exec flag (#1427)
A new rkt image gc command adds initial support for garbage collecting images from the store (#1487). This removes treeStores not referenced by any non-GCed rkt pod.
rkt list now provides more information including image version and hash (#1559)
rkt image list output now shows shortened hash identifiers by default, and human readable date formats. To use the previous output format, use the --full flag. (#1455)
rkt prepare gained the --exec flag, which restores flag-parity with rkt run (#1410)
lkvm stage1 backend has experimental support for rkt enter (#1303)
rkt now supports empty volume types (#1502)
An early, experimental read-only API definition has been added (#1359, #1518).

Bug 修复

Fixed bug in --stage1-image option which prevented it from using URLs (#1524)
Fixed bug in rkt trust‘s handling of --root (#1494)
Fixed bug when decompressing xz-compressed images (#1462, #1224)
In earlier versions of rkt, hooks had an implicit timeout of 30 seconds, causing some pre-start jobs which took a long time to be killed. This implicit timeout has been removed. (#1547)
When running with the lkvm stage1, rkt now sets $HOME if it is not already set, working around a bug in the lkvm tool (#1447, #1393)
Fixed bug preventing run-prepared from working if the metadata service was not available (#1436)

其他改进

Bumped appc spec to 0.7.1 (#1543)
Bumped CNI and netlink dependencies (#1476)
Bumped ioprogress to a version which prevents the download bar from being drawn when rkt is not drawing to a terminal (#1423, #1282)
Significantly reworked rkt’s internal use of systemd to orchestrate apps, which should facilitate more granular control over pod lifecycles (#1407)
Reworked rkt’s handling of images with non-deterministically dependencies (#1240, #1198).
rkt functional tests now run appc’s ACE validator, which should ensure that rkt is always compliant with the specification. (#1473)
A swathe of improvements to the build system
- make clean should now work
- Different rkt stage1 images are now built with different names (#1406)
- rkt can now build on older Linux distributions (like CentOS 6) (#1529)
Various internal improvements to the functional test suite to improve coverage and consolidate code
The “ACI” field header in rkt image output has been changed to “IMAGE NAME”
rkt image rm now exits with status 1 on any failure (#1486)
Fixed permissions in the default stage1 image (#1503)
Added documentation for prepare and run-prepared subcommands (#1526)
rkt should now report more helpful errors when encountering manifests it does not understand (#1471)

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Rocket （也叫 rkt）是 CoreOS 推出的一款容器引擎，和 Docker 类似，帮助开发者打包应用和依赖包到可移植容器中，简化搭环境等部署工作。Rocket 和 Docker 不同的地方在于，Rocket 没有 Docker 那些为企业用户提供的“友好功能”，比如云服务加速工具、集群系统等。反过来说，Rocket 想做的，是一个更纯粹的业界标准。

CoreOS 把它的容器称为 App Containers，里面包含 app container image、runtime、container-discovery 协议等。其中，App Container Image 和 Docker 里的 Image 比较类似，包含应用必需的元素组成，如源代码和二进制文件。Rocket runtime 则是依照 App Container 标准规格打造的，旨在将容器真正的变成一款命令行工具。