# 3.8 Service Removal

_Peios / Advanced Peios / peinit / The Service Model_

> What happens when a definition disappears from the registry, depending on whether the service is running.

When a definition disappears from `Machine\System\Services\`, peinit
learns of it through the ordinary change-notification path. What happens
next depends on whether anything is running.

## 3.8.1 Not running

An entry in Inactive, Failed, Completed, Skipped or Abandoned is
discarded immediately. There is no process to consider.

## 3.8.2 Running

An entry in Active, Starting, Reloading, Backoff or Stopping is **not**
killed. The running process is a job, and a job's lifecycle is
independent of the definition that produced it — removing a definition
stops future management, it does not terminate work in progress.

peinit marks the entry **definition-removed** and keeps the cached
definition, solely to go on supervising the instance it already has.
When that instance exits it is not restarted — `RestartPolicy` is moot,
because there is nothing left to restart from — and peinit then discards
the entry.

While an entry is definition-removed:

- it keeps satisfying its dependents for as long as the instance is
  alive, because it is still running;
- `stop` is accepted, so an administrator can drain it cleanly, using
  the cached `StopTimeout`;
- `start`, `restart` and `reload` are rejected with `UNKNOWN_SERVICE` —
  there is no definition to work from;
- `status` reports the current runtime state with `definition_removed`
  set, so the draining instance is visible rather than silent.

`definition-removed` is a flag on the existing runtime state, not a
state of its own. The state machine (§6.1) and the command × state
matrix (§10.3) are unchanged by it.

Once the instance exits or is stopped, the entry — including anything in
its fd store (§10.6) — is discarded. A dependent that `Requires` the
removed service keeps being satisfied while the instance runs; after the
entry is discarded, the dependent's next start sees an unresolved
dependency and takes the ordinary validation path.