Changing a Service Configuration

In the following example, a service configuration program uses the ChangeServiceConfig function to change the configuration parameters of an installed service. The program first tries to lock the database, to prevent the SCM from starting a service while it is being reconfigured. If it successfully locks the database, the program opens a handle to the service object, modifies its configuration, unlocks the database, and then closes the service object handle. If the program does not successfully in lock the database, it uses the QueryServiceLockStatus function to retrieve information about the lock.

VOID ReconfigureSampleService(BOOL fDisable)

{

SC_LOCK sclLock;

LPQUERY_SERVICE_LOCK_STATUS lpqslsBuf;

DWORD dwBytesNeeded, dwStartType;

// Need to acquire database lock before reconfiguring.

sclLock = LockServiceDatabase(schSCManager);

// If the database cannot be locked, report the details.

if (sclLock == NULL)

{

// Exit if the database is not locked by another process.

if (GetLastError() != ERROR_SERVICE_DATABASE_LOCKED)

MyErrorExit("LockServiceDatabase");

// Allocate a buffer to get details about the lock.

lpqslsBuf = (LPQUERY_SERVICE_LOCK_STATUS) LocalAlloc(

LPTR, sizeof(QUERY_SERVICE_LOCK_STATUS)+256);

if (lpqslsBuf == NULL)

MyErrorExit("LocalAlloc");

// Get and print the lock status information.

if (!QueryServiceLockStatus(

schSCManager,

lpqslsBuf,

sizeof(QUERY_SERVICE_LOCK_STATUS)+256,

&dwBytesNeeded) )

MyErrorExit("QueryServiceLockStatus");

if (lpqslsBuf->fIsLocked)

printf("Locked by: %s, duration: %d seconds\n",

lpqslsBuf->lpLockOwner,

lpqslsBuf->dwLockDuration);

else

printf("No longer locked\n");

LocalFree(lpqslsBuf);

MyErrorExit("Could not lock database");

}

// The database is locked, so it is safe to make changes.

// Open a handle to the service.

schService = OpenService(

schSCManager, // SCManager database

TEXT("Sample_Srv"), // name of service

SERVICE_CHANGE_CONFIG); // need CHANGE access

if (schService == NULL)

MyErrorExit("OpenService");

dwStartType = (fDisable) ? SERVICE_DISABLED :

SERVICE_DEMAND_START;

if (! ChangeServiceConfig(

schService, // handle of service

SERVICE_NO_CHANGE, // service type: no change

dwStartType, // change service start type

SERVICE_NO_CHANGE, // error control: no change

NULL, // binary path: no change

NULL, // load order group: no change

NULL, // tag ID: no change

NULL, // dependencies: no change

NULL, // account name: no change

NULL) ) // password: no change

{

MyErrorExit("ChangeServiceConfig");

}

else

printf("ChangeServiceConfig SUCCESS\n");

// Release the database lock.

UnlockServiceDatabase(sclLock);

// Close the handle to the service.

CloseServiceHandle(schService);

}

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