After you install Azure AD Connect, but before you configure the product through the Microsoft Azure Active Directory Connect wizard, you can fiddle with the Azure AD Connect installer.
Below is a list of command-line switches that you can use:
The below list is based on Azure AD Connect version 18.104.22.168.
When you have an existing ADSync database, you can use the /UseExistingDatabase command-line switch to Install Azure AD Connect by using an existing ADSync database. The new Azure AD Connect installation that is set up using this command-line switch will completely overwrite the contents of the database that was previously in use with another Azure AD Connect installation, but will use the same database name, schema, logins and permissions.
The /SkipLDAPSearch command-line switch can be used to configure Azure AD Connect to use the mS-DS-ConsistencyGUID attribute as its source anchor. By default, Azure AD Connect checks the contents of this attribute for objects in scope for synchronization, but this command-line switch instructs Azure AD Connect to skip this check. This switch is useful when you want to install a Staging Mode Azure AD Connect installation using the mS-DS-ConsistencyGUID attribute as its source anchor.
The /ForceExport command-line switch can be used to create a parallel deployment of Azure AD Connect side by side of an existing DirSync implementation. This switch exports the DirSync settings so you can then import them into Azure AD Connect using the /Migrate command-line switch below.
The /Migrate command-line switch can be used to create a parallel deployment of Azure AD Connect side by side of an existing DirSync implementation for migration purposes. This switch imports the DirSync settings into Azure AD Connect.
The /EnableLDAP command-line switch switches Azure AD Connect’s setup mode from Active Directory to an LDAPv3-compatible identity store.