Windows service trigger start – difference manual vs automatic

windowswindows-service

Since Windows Server 2008 R2 (and Windows 7 I think for the client OS) Microsoft has introduced trigger start for services. I do understand difference between automatic, automatic (delayed) and manual startup types. From what I read on googled articles, I believe I do understand logic of trigger start (though never used that).

What I'm not really sure I understand would be difference of services that are configured to automatic (trigger start) and manual (trigger start) and I had no luck to find any explanation for this.

I am sort of thinking that in both cases service is not running unless trigger will start it, so what would be the difference actually?

Reason I have encountered this question is actually monitoring of automatic startup type services. Since the service is set to start with trigger and trigger is not valid, service is not running and monitoring is reporting it the way, that automatic service is not running.

To sum up – my questions are:

  1. What is difference between automatic (trigger start) and manual (trigger start) service?
  2. Can it have any impact to service/application (in general) if service will be switched from automatic (trigger start) to manual (trigger start)?

Best Answer

Automatic services start when the OS boots. Manual services do not. Triggers can be added to services to make them start on some event, such as an ETW event, or a USB device being plugged in, etc. Triggers can be added to either Manual or Automatic services.

An example of the trigger(s) on an Automatic (Trigger Start) service:

C:\Users\Ryan>sc qtriggerinfo dnscache
[SC] QueryServiceConfig2 SUCCESS

SERVICE_NAME: dnscache

        START SERVICE
          FIREWALL PORT EVENT          : b7569e07-8421-4ee0-ad10-86915afdad09 [PORT OPEN]
            DATA                       : 5355;UDP;

An example of the trigger(s) on a Manual (Trigger Start) service:

C:\Users\Ryan>sc qtriggerinfo appinfo
[SC] QueryServiceConfig2 SUCCESS

SERVICE_NAME: appinfo

        START SERVICE
          NETWORK EVENT                : bc90d167-9470-4139-a9ba-be0bbbf5b74d [RPC INTERFACE EVENT]
            DATA                       : 201ef99a-7fa0-444c-9399-19ba84f12a1a
        START SERVICE
          NETWORK EVENT                : bc90d167-9470-4139-a9ba-be0bbbf5b74d [RPC INTERFACE EVENT]
            DATA                       : 5f54ce7d-5b79-4175-8584-cb65313a0e98
        START SERVICE
          NETWORK EVENT                : bc90d167-9470-4139-a9ba-be0bbbf5b74d [RPC INTERFACE EVENT]
            DATA                       : fd7a0523-dc70-43dd-9b2e-9c5ed48225b1
        START SERVICE
          NETWORK EVENT                : bc90d167-9470-4139-a9ba-be0bbbf5b74d [RPC INTERFACE EVENT]
            DATA                       : 58e604e8-9adb-4d2e-a464-3b0683fb1480

A service can be set to Automatic, so that it starts as soon as the OS loads, but it can also stop gracefully on its own when the service has no more work to do. After it has stopped, a trigger can start it again at any time.

So to recap, both Automatic and Manual services can have triggers that manually start them. The only difference is that Automatic services start as soon as the operating system loads.

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