Aleksa Sarai

Aleksa combines sustained maintenance of runc with the creation of umoci, now used by image-building systems and container projects including Open Build Service, LXC and Incus. These contributions help engineers build compatible container images and protect host systems when running applications. Practical writing about umoci also makes the underlying tools easier to understand and use.

Aleksa Sarai is a Founding Engineer at Amutable, working to verify the integrity of Linux systems from build through to operation. Based in Sydney, Aleksa joined after a decade on SUSE’s containers team, continuing long-term maintenance of runc and umoci to support container-building infrastructure and secure host systems.

Development of umoci began in 2016 so that SUSE’s Kiwi build system could generate container images without requiring Docker. The tool became the reference implementation of the Open Container Initiative image specification and was adopted by systems including SUSE’s Open Build Service, LXC, Incus and Stacker, followed by a May 2025 v0.5 release article detailing that background. Alongside tooling work, Aleksa regularly patches container isolation flaws in runc, including a June 2026 fix for a path-handling issue that permitted limited file changes outside a container.