Ubuntu Core 26

Released: 14th May 2026

Ubuntu Core 26 (UC26) is the latest Ubuntu Core release, and is built on the foundations of Ubuntu 26.04 LTS (Resolute Raccoon).

With up to 15 years of security maintenance, Ubuntu Core is a minimal, immutable OS that enables developers to build and deploy production-grade images for embedded devices on various architectures at any scale.

Ubuntu Core 26 includes system-level improvements in update performance, OTA update sizes (reduced by up to 90%), and image composition through Chisel.

Key updates in this release include:

  • Chisel-based build system

  • Update time improvements

  • CRA compliance

  • Livepatch support

  • Components general availability

  • New API documentation

Now built with Chisel

Ubuntu Core 26 uses a Chisel-based build system for base snap composition. It relies on release-specific package slice definitions to enforce explicit, traceable dependencies.

Every file in the filesystem can now be attributed to its originating slice and source package, improving the accuracy of integrity checks and vulnerability triage.

The new build system also contributes to a 7% reduction in base image size.

Improved update time

An updated snap-delta format reduces update sizes for most snaps.

Updates to core base snaps decrease from 16MB to 1.5MB. These changes are paired with boot optimizations and initramfs-based installation paths that avoid redundant reboots by default.

CRA compliance

The EU Cyber Resilience Act (CRA) requires products to be secure by default, supported over the long term, and backed by clear accountability across the software stack.

Ubuntu Core addresses these requirements through secure design, software traceability, and modular architecture with well-defined responsibility boundaries.

Canonical assumes Manufacturer responsibilities for the operating system release cycle by providing security maintenance for Ubuntu Core core modules, continuous CVE monitoring and coordinated disclosure, and compliance with IEC 62443-4-1.

Livepatch support

Canonical Livepatch is supported in Ubuntu Core 26.

This means devices can now receive critical kernel security updates without a reboot, reducing disruption for always-on systems.

Fleet management

For fleet observability, Ubuntu Core 26 integrates with the Canonical Observability Stack, built on Juju and Kubernetes. Ubuntu Core can stream logs and metrics from devices to centralized Grafana, Loki, and Prometheus infrastructure deployed in cloud or on-premise environments.

Components general availability

First tested in Ubuntu Core 24 for delivering NVIDIA drivers, components are now generally available. They allow snap maintainers to distribute large or optional resources, such as debug symbols, translations, or optional drivers, alongside the main snap without increasing the base installation footprint.

New API documentation

The Snapd REST API is now OpenAPI compliant and includes overhauled Swagger-based documentation.

This provides a machine-readable API definition that supports endpoint discovery, request and response validation, and client generation with standard OpenAPI tools. It also improves consistency between the documentation and API behavior, making automation easier to test and maintain across releases.

See the Snapd REST API reference for details.

Further improvements

This release adds many other new features, including:

From this release onwards, the Python environment in the core base snap won’t be available at runtime. See Bundled Python changes for Ubuntu Core 26 for more details.