#layover — Public Fediverse posts on home.social

MaddieM4 @[email protected] · 2026-08-20 · 16:37 UTC

This is related strongly in my mind to atomic package management, like the design of #Layover. Taking an existing filesystem full of package-owned files and user modifications, which could be in any infinite complex state (even a list of installed packages is simplifying the reality) and modifying it with a set of updates? That's a hard problem that bigger and better-resourced teams than me have struggled with. Apt is considered pretty sturdy and intentionally boring, and you still have to fix broken packages sometimes.

So I just don't do that. You make a new version of your system files, and you only switch to it when you've 100% successfully built it. Now you're doing one, very consistent and easily tested kind of thing for initial install, upgrades, designing your own live USB, etc. Keeping initial installs/live experiences in working order means upgrades also still work* "for free", and vice versa.

*there are still some edges, but with a lot less surface area, and easier to untangle if you make knots.

#layover

MaddieM4 @[email protected] · 2026-08-03 · 15:57 UTC

So this tension I think is primarily on the #MercuryMicrokernel side to resolve. The goals with #Layover are to be more impartial and platform-portable: if you have a sandbox tech available and the ability to atomically rename directories (or at least atomically rewrite symlinks), it should be possible to make Layover work there, with some degree of platform-specific code. So Mercury needs to expose those things, and that's totally feasible.

This ends up being a really useful pressure on the OS design, to make something very intentionally sandbox-oriented from the ground up - as a permeating design concern with greenfield liberty. It requires thinking in terms of resource quotas (particularly job slots a la GNU Make jobserver rationale), daemon partitioning, and probably no kernel-universal PIDs. Ideally a container workflow doesn't require special tools, it's just the native way services are downloaded, built, and run.

#mercurymicrokernel #layover

MaddieM4 @[email protected] · 2026-08-03 · 15:47 UTC

So here's where I explain what tension I was originally talking about. I have two big projects I'm excited to work on, once the groundwork is laid. One of them is a package manager/software build system called #Layover, which is reasonably but irreverently summarizable as "imagine if Nix was good." Its fundamental premise is treating immutable directories of data as a logical datatype, and supporting both pure and impure operations on these directories (where the pure ones are incentivized by cacheability, remote build compatibility, etc). Its intention is to be able to work across multiple platforms, using whatever platform-specific isolation tech is available for build sandboxing.

The other tech is the #MercuryMicrokernel, which is far less formed in design right now, but will radically reject POSIX compliance in favor of high-performance async IPC and a simplified FS design that omits ownership and permission data in favor of Plan9-ish "views" and #Prone-like COW semantics.

I'd like these to get along.

#layover #mercurymicrokernel #prone

MaddieM4 @[email protected] · 2026-08-03 · 15:27 UTC

One of the proto-verbal design tensions I'm turning over in the back of my mind lately is about the axes that are actually appropriate for subdividing a single-host computing environment into multiple mutually-isolated functional domains. Which is a lot of highfalutin' words, so let me point at a familiar landmark: Docker.

It's pretty easy to say Docker sucks, or containers suck (there are valid arguments there), but they don't tend to appreciate why Docker got so popular in the first place - how containers act like a "desire path" in computing. There's something important there that people needed, and even doing an approximate job with a little marketing was enough to take off in adoption dramatically. Downloadable, portable, manipulable, standardized, self-contained, with the ability to share pieces of the host FS or not, and similar flexibility for networking. Obviously that beats a world of accommodating the quirks of umpteen Linux distros.

#MercuryMicrokernel #Layover

#mercurymicrokernel #layover