feat(nix): bound the store, generations and boot menu (task 0014) #7

alexion · 2026-07-20T10:22:01-04:00

alexion commented

2026-07-20 10:22:01 -04:00

Task: .claude/tasks/0014-nix-store-housekeeping.md

Bounds the three things that grew without limit on this machine, declared in the shared base config so every future host inherits them:

Weekly garbage collection, deleting generations older than 30 days.
Weekly store optimisation on a timer rather than at build time.
Retained boot configurations capped at 15.

Verified with nix flake check, plus inspection of the built toplevel: both timers are present, and the bootloader installer carries CONFIGURATION_LIMIT = int("15").

Deviations. The schedules are named days rather than the bare weekly keyword — systemd expands weekly to Mon *-*-* 00:00:00, which would have started collection and deduplication at the same instant, leaving nix-optimise hard-linking paths nix-gc was concurrently deleting. Collection runs Mon 03:15, optimisation Thu 03:45.

Review

Overall: MEDIUM

Blast radius: Medium — one file, but the base every host imports, so the timers and boot-entry cap land on all machines.
Reversibility: Medium — the lines revert trivially, their effects do not; once GC or the cap prunes a generation, that rollback target is gone.
Test coverage: Medium — nix flake check catches a bad option name or type, but nothing exercises the timers over time.
Sensitive domain: Low — no auth, secrets or permissions touched.
Size & complexity: Low — five declarative assignments, no logic.
Runtime criticality: Medium — bootloader state, and GC deleting a needed generation is exactly the recovery path this preserves.

Unaddressed findings

Standards, judgement call. Retention is expressed twice with no stated relationship — --delete-older-than 30d and configurationLimit = 15 — and the comment convention forbids either comment pointing at the other. Left as is: they bound different resources (store versus EFI partition), and merging them into one block would misdescribe both.
Spec, noted not fixed. The cap is set unconditionally in the shared base, so a future host on another bootloader inherits no cap. The task asks for it there, and the option is inert rather than an error off systemd-boot.
Spec, open criterion. "Manual confirmation after a rebuild" is unmet — it needs a nixos-rebuild switch, and this session had no sudo credential. It closes in a follow-up commit, as tasks 0013, 0016 and 0017 did.

Task: `.claude/tasks/0014-nix-store-housekeeping.md` Bounds the three things that grew without limit on this machine, declared in the shared base config so every future host inherits them: - Weekly garbage collection, deleting generations older than 30 days. - Weekly store optimisation on a timer rather than at build time. - Retained boot configurations capped at 15. Verified with `nix flake check`, plus inspection of the built toplevel: both timers are present, and the bootloader installer carries `CONFIGURATION_LIMIT = int("15")`. **Deviations.** The schedules are named days rather than the bare `weekly` keyword — systemd expands `weekly` to `Mon *-*-* 00:00:00`, which would have started collection and deduplication at the same instant, leaving `nix-optimise` hard-linking paths `nix-gc` was concurrently deleting. Collection runs `Mon 03:15`, optimisation `Thu 03:45`. ## Review **Overall: MEDIUM** - Blast radius: Medium — one file, but the base every host imports, so the timers and boot-entry cap land on all machines. - Reversibility: Medium — the lines revert trivially, their effects do not; once GC or the cap prunes a generation, that rollback target is gone. - Test coverage: Medium — `nix flake check` catches a bad option name or type, but nothing exercises the timers over time. - Sensitive domain: Low — no auth, secrets or permissions touched. - Size & complexity: Low — five declarative assignments, no logic. - Runtime criticality: Medium — bootloader state, and GC deleting a needed generation is exactly the recovery path this preserves. ### Unaddressed findings - **Standards, judgement call.** Retention is expressed twice with no stated relationship — `--delete-older-than 30d` and `configurationLimit = 15` — and the comment convention forbids either comment pointing at the other. Left as is: they bound different resources (store versus EFI partition), and merging them into one block would misdescribe both. - **Spec, noted not fixed.** The cap is set unconditionally in the shared base, so a future host on another bootloader inherits no cap. The task asks for it there, and the option is inert rather than an error off systemd-boot. - **Spec, open criterion.** "Manual confirmation after a rebuild" is unmet — it needs a `nixos-rebuild switch`, and this session had no sudo credential. It closes in a follow-up commit, as tasks 0013, 0016 and 0017 did.

alexion added 1 commit 2026-07-20 10:22:02 -04:00

feat(nix): bound the store, generations and boot menu (task 0014) c63c3079be

Garbage collection and store optimisation each run weekly, on separate
days so they never contend, and retained boot configurations are capped
at 15.

alexion added 1 commit 2026-07-20 10:27:42 -04:00

docs: close out task 0014 after confirming the timers 0d685ce277

alexion merged commit 0d685ce277 into main

2026-07-20 10:43:51 -04:00

alexion deleted branch task-0014-nix-store-housekeeping

2026-07-20 10:43:51 -04:00

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Reference: alexion/dotfiles#7