Administering Core Business Intelligence Services - Microsoft SQL Server 2008 R2 Administration - page 164

9. On the Server Configuration | Service Accounts page, specify login accounts

for SQL Server Database Engine, SQL Server Agent, Integration services, and
SQL Server Browser.

10. You can assign the same login account to all SQL Server services using the same
account for all SQL Server services, or you can configure each service account
individually. Choose StartUp option as Automatic for SQL Server Database Engine
and SQL Server Integration Services.

A Best practice is to configure service accounts individually to provide
least privileges for each service, where SQL Server services are
granted the minimum permissions they have to complete their tasks.

11. SQL Server Setup enforces the domain user-account requirement by blocking the
installation whenever a machine account is specified.
12. At the Database Engine Configuration | Account provisioning page, we have an
option to set the security mode and assign an account to be a member of SYSADMIN
fixed server role.