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environment facts: pi alignment done by a pinned package input on .27 and .51

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Sam
2026-11-12 14:28:15 +11:00
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@@ -136,34 +136,57 @@ What was changed:
- Local git repo only, one commit, no remote. It is not on Gitea. Push it somewhere before
relying on it, or accept that only this machine has it.
## NixOS alignment for Pi, 2026-11-11
## NixOS alignment for Pi, measured 2026-11-12
Goal: all three machines on the same Pi. The `pi-coding-agent` version comes from the nixpkgs pin,
so aligning means bumping `nixpkgs` and `home-manager` in each machine's flake.
Goal: the same Pi on all three machines. `pi-coding-agent` comes from nixpkgs, so aligning used to
mean bumping the whole system on each machine. That is what broke `.13`: `nixos-rebuild switch`
restarts every changed unit in place, the network units restarted, the default route did not come
back, and every service that needs the network died with it. Exit code 4 meant "units failed to
start", not "the build failed" - the generation had already switched.
Measured after `nix flake update nixpkgs home-manager`:
**The rule that follows: on a machine someone is using, a nixpkgs-sized change goes in with
`nixos-rebuild boot` and a reboot, never `switch`.**
| machine | nixpkgs pin | pi after update | state |
### What was done instead, and why it is safe
Pi is one package. Instead of moving a whole system to a new nixpkgs, a second flake input pinned
to one revision provides only that package:
```nix
nixpkgs-pi.url = "github:NixOS/nixpkgs/f4a03c008967841f2a0b3cb7c436fc6fc31671f6";
# in the let block
piPkgs = import nixpkgs-pi { inherit system; config.allowUnfree = true; };
# in home-manager users.${user}.home.packages
piPkgs.pi-coding-agent
```
and `pi-coding-agent` was removed from `home/sam/home.nix` so exactly one `pi` is on `PATH`. The
system pin on those machines did not move, so nothing else in the system changes and no network or
service unit is restarted. Remove the input once the system pins are aligned for real.
### State, verified by building, not switching
| machine | method | pi in the built system | store path |
|---|---|---|---|
| `.13` | 2026-07-29 → 2026-11-07 | **1.5.0** | config ready, 12 derivations to build |
| `.27` | same | 1.5.0 | evaluation fails in home-manager fontconfig |
| `.51` | 2026-09-26 | 0.87.1 (today) | not started |
| `.13` nixos-desktop | full nixpkgs bump (2026-11-07), **running** | 1.5.0 | `4yxlfj0sw5hlk7x1hiv0igm0dckg8rv9` |
| `.27` sam-4screen-desktop | `nixpkgs-pi` input, built, **not yet switched** | 1.5.0 | `4yxlfj0sw5hlk7x1hiv0igm0dckg8rv9` |
| `.51` sam-thinkpad | `nixpkgs-pi` input, built, **not yet switched** | 1.5.0 | `4yxlfj0sw5hlk7x1hiv0igm0dckg8rv9` |
Two changes are needed with the bump, both measured:
One store path on all three: the same bytes of Pi, not merely the same version number.
1. `programs.zsh.initExtra` was renamed: `initContent`.
2. **lan-mouse 0.11.0 panics** when `LIBGIT2_NO_VENDOR` is set and there is no system libgit2
(nixpkgs 2026-11-07 sets it). An overlay on `pkgs.lan-mouse` did **not** fix it — the
derivation hash barely moved and the same panic came back. What does work is building the
flake's own lan-mouse package with `LIBGIT2_NO_VENDOR = "0"`:
### Two other things measured on the way
```nix
lm = lan-mouse.packages.${system}.default.overrideAttrs (o: { LIBGIT2_NO_VENDOR = "0"; });
```
- `programs.zsh.initExtra` is `initContent` in home-manager 2026-11. Both names evaluate on the
older home-manager, so the rename is safe in either direction.
- **lan-mouse 0.11.0 panics** when `LIBGIT2_NO_VENDOR` is set and no system libgit2 exists; nixpkgs
2026-11-07 sets it. An overlay on `pkgs.lan-mouse` does **not** help. Building the flake's own
package with the variable off does:
and using `lm` in `systemPackages` instead of the plain package. Built and verified:
`/nix/store/f6w228jqp5wq6xznf6arq69kck6axyyf-lan-mouse-0.11.0`.
```nix
lm = lan-mouse.packages.${system}.default.overrideAttrs (o: { LIBGIT2_NO_VENDOR = "0"; });
```
`.27`'s failure names `home-manager.users.sam.fonts.fontconfig.configFile.fonts.settings`. It is a
home-manager option merge, not the Pi change. The smaller next attempt there is to bump `nixpkgs`
only and leave `home-manager` where it is.
`.13` now lists `lm` in `systemPackages` instead of `lan-mouse`.
- `.27`'s full-system bump failed in `home-manager.users.sam.fonts.fontconfig.configFile.fonts.settings`
(`recursiveUpdateUntil` / `head values`). The `nixpkgs-pi` route avoids it entirely; it is still
an open item for the day the system pins are aligned.