What is "Type" on a service?

Question

If you look on Regedit for HKLM\SYSTEM\CurrentControlSet\services there are a lot of key, one of them if "Type", that assumes a range of values (0x1, 0x10, 0x16, etc), someone know what is this?

Answer 1

Microsoft Support - CurrentControlSet\Services Subkey Entries (along with other associated keys and values). I'm guessing you can add the hex values to represent more than one type with each service.

Here are the contents from the Microsoft Support page:

The Services subkeys under the following registry path contain parameters for the device drivers, file system drivers, and Win32 service drivers:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services

The name of each Services subkey is the name of the service, which is also the root of the name of the file from which the service is loaded. For example, for the serial mouse, the service name and Services subkey name is Sermouse. The file from which this is loaded is:

SystemRoot\SYSTEM32\DRIVERS\SERMOUSE.SYS.

All service names are defined under:

 HKEY_LOCAL_MACHINE\SOFTWARE.

The names of the Windows NT built-in network services such as the Alerter and Browser services are defined under the Microsoft\Windows NT\CurrentVersion subkey in the Software area of the Registry.

Each Services key can have additional subkeys. Many services have a Linkage subkey, which provides data for binding network components, as described in "Linkage Subkey Entries for Network Components," in the article "Network Adapter Cards Entries, PART 1." Many services also have a Parameters subkey that contains entries defined by the service with values for configuring the specific service.

Values for Parameters subkeys and other service-specific entries are described in these articles:

Network Adapter Cards Entries Device Drivers Entries Network Services Entries

The following standard value entries appear for each Services subkey:

ErrorControl REG_DWORD Error constant Specifies the level of error control for the service as follows:

Error Control Meaning Level

0x3 (Critical) Fail the attempted system startup. If the startup is not using the LastKnownGood control set, switch to LastKnownGood. If the startup attempt is using LastKnownGood, run a bug-check routine.

0x2 (Severe) If the startup is not using the LastKnownGood control set, switch to LastKnownGood. If the startup attempt is using LastKnownGood, continue on in case of error.

0x1 (Normal) If the driver fails to load or initialize, startup should proceed, but display a warning.

0x0 (Ignore) If the driver fails to load or initialize, start up proceeds. No warning is displayed.

Group REG_SZ Group name Specifies the name of the group of which the particular service is a member. Default: (null)

DependOnGroup REG_MULTI_SZ Group name Specifies zero or more group names. If one or more groups is listed, at least one service from the named group must be loaded before this service is loaded. Default: (empty)

DependOnService REG_MULTI_SZ Service name Specifies zero or more Services subkey names. If a service is listed here, that named service must be loaded before this service is loaded. Default: (empty)

ImagePath REG_DWORD Path and filename Specifies a path name. For adapters, this value is ignored. Default: For a driver:

 systemroot\SYSTEM32\DRIVERS\driverName.SYS

For a service:

 systemroot\SYSTEM32\serviceName.EXE

(where driverName or serviceName is the same as the related Services subkey name)

ObjectName REG_DWORD Object name Specifies an object name. If Type specifies a WIN32 Service, this name is the account name that the service will use to log on when the service runs. If Type specifies a Kernel driver or file system driver, this name is the Windows NT driver object name that the I/O Manager uses to load the device driver. Default: subkeyName

Start REG_DWORD Start constant Specifies the starting values for the service as follows:

START TYPE LOADER MEANING

0x0 Kernel Represents a part of the (Boot)
driver stack for the boot (startup) volume and must therefore be loaded by the Boot Loader.

0x1 I/O Represents a driver to be loaded (System)
subsystem at Kernel initialization.

0x2 Service To be loaded or started (Auto load)
Control automatically for all startups, Manager regardless of service type.

0x3 Service Available, regardless of type, (Load on
Control but will not be started until demand) Manager the user starts it (for example, by using the Devices icon in Control Panel).

0x4 Service NOT TO BE STARTED UNDER ANY (disabled)
Control CONDITIONS. Manager

The Start value is ignored for adapters. If Type is a Win32 Service value (as described below), the Start value must specify an Auto, Demand, or Disabled value.

Tag REG_DWORD Specifies a load order within a given group. The value of Tag specifies a number that is unique within the group of which the service is a member. The related GroupName entry under the Control\GroupOrderList subkey specifies a list of tags, in load order.

For example, the following services that are members of the Primary Disk group could have these values: Tag=4 for the Abiosdsk subkey, Tag=2 for Atdisk, Tag=1 for Cpqarray, and Tag=3 for Floppy. The value for Primary Disk under the GroupOrderList subkey will use these Tag values to specify the defined order for loading these services. As another example, each SCSI miniport service has a unique Tag value that is used as an identifier in the SCSI miniport value under the GroupOrderList subkey to define which SCSI adapter to load first.

Type REG_DWORD Type constant

Specifies the type of service as follows:

Service Type Description

0x1 A Kernel device driver.

0x2 File system driver, which is also a Kernel device driver.

0x4 A set of arguments for an adapter.

0x10 A Win32 program that can be started by the Service Controller and that obeys the service control protocol. This type of Win32 service runs in a process by itself.

0x20 A Win32 service that can share a process with other Win32 services.

For example, when you start Windows NT, the Boot Loader scans the Registry for drivers with a Start value of 0 (which indicates that these drivers should be loaded but not initialized before the Kernel) and a Type value of 0x1 (which indicates a Kernel device driver such as a hard disk or other low-level hardware device driver). The drivers are then loaded into memory in the order specified as the List value in CurrentControlSet\Control\ServiceGroupOrder.