Document the logic around X-NotSocketActivated in the manual

    before the activation script is run. This behavior is different when the

    service is socket-activated, as outlined in the following steps.

  - The last thing that is taken into account is whether the unit is a service

    and socket-activated. If `X-StopIfChanged` is **not** set, the service

    is **restart**ed with the others. If it is set, both the service and the

    socket are **stop**ped and the socket is **start**ed, leaving socket

    activation to start the service when it's needed.

  - The last thing that is taken into account is whether the unit is a

    service and socket-activated. A correspondence between a

    `.service` and its `.socket` unit is detected automatically, but

    services can **opt out** of that detection by setting

    `X-NotSocketActivated` to `yes` in their `[Service]`

    section. Otherwise, if `X-StopIfChanged` is **not** set, the

    service is **restart**ed with the others. If it is set, both the

    service and the socket are **stop**ped and the socket is

    **start**ed, leaving socket activation to start the service when

    it's needed.

## Sysinit reactivation {#sec-sysinit-reactivation}