Inside Alibaba Cloud Linux 2: New Features, Kernel Innovations & QA

1. Open‑Source Background

Alibaba Cloud Linux 2 (Aliyun Linux 2) was open‑sourced in April 2019 as a next‑generation Linux distribution optimized for Alibaba Cloud ECS, built on CentOS 7, LTS kernel sources, and various Alibaba open‑source projects.

Open‑Source History

The development team originates from Alibaba's OS team (formerly Taobao kernel group) with nine years of kernel experience. The distribution combines community upstreams with Alibaba‑specific enhancements and is offered alongside CentOS and Ubuntu as official ECS images.

2017: Aliyun Linux 17.01 based on CentOS 7.3 with a 4.4 kernel was released.

Oct 2018: Alibaba Cloud Linux 2 project was approved.

Mar 1 2019: Beta released for angel customers.

Apr 2 2019: GA released and listed in ECS official images.

Source code published on Alibaba OPSX and kernel on GitHub.

2. Features and Advantages

2.1 Initial Version Features

The core update is a custom 4.19 LTS kernel with many cloud‑oriented enhancements:

CPU: security fixes and load‑prediction improvements.

Memory: TLB, writeback, OOM‑killer reliability, idle page tracking.

File systems: new features for Ext4, XFS, Btrfs, NFS, OverlayFS.

IO: asynchronous I/O optimizations.

Network: BBR, zero‑copy TCP API, XDP/AF_XDP support.

cgroup: v2 support, writeback, blkio latency.

Additional kernel‑related improvements include boot parameter tuning, Kdump support, and live‑patching capability.

2.2 Updates and Development

★ 2.2.1 System Image Updates

Two image updates have been released in the past three months; the latest image ID is aliyun_2_1903_64_20G_alibase_20190619.vhd. Initially, images were only purchasable via the ECS console; since May 2019, downloadable qcow2 images supporting QEMU/KVM and cloud‑init are available.

★ 2.2.2 Package Updates

YUM repositories are kept up‑to‑date; users can run yum update to get the latest packages. The kernel is rebased on the 4.19 LTS source with Alibaba‑specific patches and bug fixes, released roughly every three to four weeks.

BaseOS packages such as crash, e2fsprogs, xfsprogs, and iproute are updated and tested.

Integrated Alibaba open‑source projects include:

Alibaba Dragonwell (Ali‑JDK)

PouchContainer

Dragonfly client

Tengine (enhanced Nginx)

aliyun‑cli

ossfs

eBCC

★ 2.2.3 Cloud Kernel Community Contributions

The Cloud Kernel is the open‑source kernel of Alibaba Cloud Linux 2. The team contributes patches to the upstream LTS kernel and submits back‑ports, with 19 patches accepted by June 30. Contributions also include test cases for LTP and xfstests, and collaborations with Intel 0‑day project.

★ 2.2.4 Important Kernel Features

Two recent self‑developed kernel features are highlighted:

(a) cgroup writeback v1

Implemented for cgroup‑v1 after user feedback, with documentation and default disabled state.

(b) TCP TIME‑WAIT timeout interface

Allows dynamic adjustment of TIME‑WAIT timeout for short‑connection workloads, with risk warnings and released on GitHub.

3. Quality Assurance in Development

The team uses community test suites, the Beaker testing framework for nightly regression, and an internal QA team with over 40 test suites covering functional, performance, smoke, and stability testing before each release.

4. Future Plans

Continue developing new features and upstream community contributions.

Improve documentation to attract more contributors.

Share technical articles and organize online/offline events for OS and kernel communities.

5. Conclusion

Alibaba Cloud Linux 2 showcases a cloud‑optimized, open‑source Linux distribution with active development, extensive QA, and community collaboration. The project invites interested engineers to join the effort (contact: [email protected]).

References

Cloud Kernel GitHub: https://github.com/alibaba/cloud-kernel

Independent image documentation: https://github.com/alibaba/cloud-kernel/wiki/Aliyun-Linux-2-On-Premise-Image

cgroup writeback v1 release: https://github.com/alibaba/cloud-kernel/releases/tag/alk-release-12

cgroup writeback v1 docs: https://github.com/alibaba/cloud-kernel/wiki/cgroup-writeback-v1-interface

tcp_tw_timeout release: https://github.com/alibaba/cloud-kernel/releases/tag/alk-release-13

Beaker testing platform: https://beaker-project.org/