Activation

Reports system generation changes during NixOS activation.

Purpose

Provide visibility into what changed between system generations by comparing the previous and newest generation during NixOS activation, so each upgrade shows a readable package and closure diff.

Entry Point

• Main file: activation.nix

Architecture / Services / Scope

When enabled, the module installs an activation script (system.activationScripts.report-changes) that:

• locates the previous and newest system profile generations under /nix/var/nix/profiles,
• resolves both links to their store paths, and
• runs nvd diff between them.

If no previous generation exists yet, the script does nothing.

Operational Notes / Assumptions

• Diff output is informational only; the script tolerates a non-zero nvd exit so activation never fails because of a diff error.
• Default follows top-level core.enable, so most hosts get generation diff reporting automatically.