Init is systemd

Context

The init system determines service supervision, sandboxing primitives, boot, logging, credential storage and boot assessment.

The three plans

• Grok: dinit or s6; systemd only if vendor GPU units force it (Q-4).
• Fable, Codex: systemd, implied by NixOS.

Decision

systemd. It follows from NixOS, and it supplies what the nervous system needs without building it: unit sandboxing directives for every daemon, journald as the structured log source for facts, socket activation for the stem and sessions, systemd-boot with boot counting for the immune system, systemd stage-1 with native TPM2 unlock, systemd-creds for sealed secrets, and transient units for per-user execution.

Consequences

• Boot-time and idle-memory budgets are measured and published rather than assumed small.
• The stem’s operations map onto switch-to-configuration-ng, bootctl, systemd-bless-boot.
• dinit/s6 expertise is not needed; systemd’s is.

Alternatives rejected

• dinit / s6 / runit: smaller, but would require a non-NixOS base or a fork of NixOS’s module system, and would lose boot counting, credentials and sandboxing directives.