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\ServicesThe 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 subkey 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," later in this chapter. 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 sections in this chapter:
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 level | Meaning |
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_DWORD Group name
Specifies the name of the group of which the particular service is a member.
Default: (null)
DependOnGroup REG_DWORD 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_DWORD 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 driver stack for the boot (startup) volume and must therefore be loaded by the Boot Loader. |
0x1 | I/O subsystem | Represents a driver to be loaded at Kernel initialization. |
0x2 | Service Control Manager | To be loaded or started automatically for all startups, regardless of service type. |
0x3 | Service Control Manager | Available, regardless of type, but will not be started until the user starts it (for example, by using the Devices icon in Control Panel). |
0x4 | Service Control Manager | Not to be started under any conditions. |
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 ltags, 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.