Introducing the Dualayer Hierarchy Standard

Today we publish the Dualayer Hierarchy Standard (DHS) 1.0, the specification of the filesystem layout Zainium OS is built on.

Dualayer joins dual and layer: the system is built from layers, and two C libraries — musl and glibc — live in it side by side.

What it defines

• A root directory with only /overlayer, user data and the virtual filesystems — no /usr, /lib64 or /etc.
• Layers with one owner each: the system layer (syshub), the userland layer and the ignition layer, composed into one view at boot with OverlayFS.
• A directory per C library, named after its target triplet, with rules for loaders, library search paths, shared configuration and toolchains — so musl and glibc never conflict.
• Two designs: a musl base with glibc added (Zainium OS), or a glibc base with musl added. Whether the second C library ships in the base or as a package is each distribution's choice.

DHS builds on three decades of the Filesystem Hierarchy Standard, now maintained by freedesktop.org. It is licensed under CC BY-SA 4.0 and open to other distributions.

• About the standard
• Read the specification (PDF)
• Source on GitHub