# 10.4 reload-config

_Peios / Advanced Peios / peinit / The Control Interface_

> A full atomic re-read of the registry rather than a live update — what changes, and how removals and the compiled-in service are handled.

`reload-config` takes a fresh snapshot of the configuration from the
registry. It does not live-update anything.

It is also the path a registry change notification takes: any drained
watch event triggers the same full reload, rather than a targeted
re-read of whatever changed.

## 10.4.1 Atomicity

peinit reads everything first. Every registry read happens before any
mutation, so a read failure returns an error with nothing touched. It
then builds and validates a complete new graph in memory, and only swaps
it in if validation succeeds.

If validation fails, the previous generation stays live and the findings
are returned to the caller. This is where the reload path differs
sharply from boot: boot marks individual services Failed and carries on,
because it has to produce a running system; reload rejects the whole
thing, because it has a running system already and a half-applied
configuration would be worse than the one in place.

## 10.4.2 What changes

- Every service definition is re-read.
- A new dependency graph is built and validated.
- Running services are unaffected and continue on their activation
  generation.
- New definitions take effect at the next start, restart, or trigger.
- New services become available for `start` immediately.
- Timer triggers are re-evaluated and every calendar timer is re-armed,
  from the current time and with no catch-up.

A reload also refreshes things that are not service definitions: the
control descriptor, the three control socket limits, the log
configuration, the shutdown settings, the global environment layer, and
the eventd log socket path. It also prunes the fd stores of services
that no longer exist.

## 10.4.3 Removals and the compiled-in service

A definition that has disappeared is handled by §3.8 — discarded if
nothing is running, marked definition-removed if something is.

registryd is exempt. Its compiled-in definition survives a reload that
does not mention it, and its provenance survives a registry entry that
shadows it. peinit started registryd before the registry existed, and a
reload finding no definition for it cannot conclude that it should stop
being managed.