UAPI Group Specifications #

• Boot Loader Specification: Defines a set of file formats and naming conventions to allow distribution independent boot loader menus supportable by multiple bootloaders. ( canonical online location)
• Configuration Files Specification: Standardises default locations and environment variables for locating common files or base directories. This is derived from, and extends, the XDG Base Directory Specification, to allow for separation between vendor and admin configuration files, drop-in files, and masking. ( canonical online location)
• Discoverable Partitions Specification: Discusses GUID UUIDs for auto-discovery of partition semantics and mount points. ( canonical online location)
• Discoverable Disk Image: Describes the Discoverable Disk Image format for self-describing system images. ( canonical online location)
• Extension Image: Describes the use of Discoverable Disk Images to create extensions to a base image. ( canonical online location)
• Linux File System Hierarchy: Describes the layout of directories and files in an installation of Linux ( canonical online location)
• File Hierarchy for the Verification of OS Artifacts (VOA): Describes the use of Discoverable Disk Images to create extensions to a base image. ( canonical online location)
• Unified Kernel Image: Describes the use of UEFI PE binaries to provide a Unified Kernel Image containing the kernel, initrd, command line, and other components. ( canonical online location)
• Version Format Specification: Defines semantics of version strings used in the other specifications listed here. ( canonical online location)
• Linux TPM PCR Registry: An informative list of how TPM PCRs are used on a Linux system. ( canonical online location)
• Package Metadata for Executable Files: Describes the format and mechanism to include packaging metadata in ELF/PE binaries. ( canonical online location)
• Dlopen Metadata for ELF Files: Describes the format and mechanism to include dynamically loaded libraries metadata in ELF binaries. ( canonical online location)

Work in Progress #

See open PRs on github.

License #

All specifications are licensed under CC-BY-4.0.

Versioning #

All specifications are versioned.

The versioning format is MAJOR.MINOR. Compatible changes increment the MINOR version. Incompatible changes increment the MAJOR version and reset the MINOR version to 0.

Work in progress specifications have a MAJOR version of 0.

A filename/MAJOR.MINOR git tag will be created when a new version of a given spec is released.

Glossary #

This section clarifies on terms and abbreviations used in specs and other documents.

General terms and abbreviations #

• MOK – Machine Owner Key (shim)
• PCR – TPM Platform Configuration Registers
• TPM – Trusted Platform Module (security chip)
• SBAT – UEFI Secure Boot Advanced Targeting

Terms and abbreviations specific to UAPI group specifications #

• DDI - Discoverable Disk Image
• DPS - Discovery Partition Specification
• UKI - Unified Kernel Images (UEFI boot stub + kernel + initrd + more)
• BLS - Boot Loader Specification
• sysext – System Extension Image (type of DDI that is overlayed on top of /usr/ and /opt/ via overlayfs and can extend the underlying OS vendor resources in a composable, immutable fashion)
• confext – Configuration Extension Image (type of DDI that is overlayed on top of /etc/ via overlayfs and can extend the underlying OS’ configuration in a composable, immutable fashion)

Participate #

Please use the specifications issue tracker to engage with the project.