aa363691_leged_Installation___Nik_Patel__2
[0] Search Service Account (e.g. sp_search) [1] Specify this account as Search Service Account while provisioning Search Service Application from the Manage Service Application page This account runs the SharePoint Server Search Windows Service, which is used by all Search Service Applications. For any given server, there is only one instance of this service. [3] None [4] None [5] AD Group Membership Changes – After you provision Search Service, machine-level permission is configured automatically: Member in the WSS_WPG. SQL Database Changes – After you provision Search Service, SQL Server and database permissions are configured automatically: This account is assigned to the WSS_CONTENT_APPLICATION_POOLS role associated with the farm configuration database. This account is assigned to the WSS_CONTENT_APPLICATION_POOLS role associated with the SharePoint_Admin content database. After you provision Search Service, service account is granted access to the propagation location share (or shares) on all search query servers in a farm. [2] 
Domain User Account. Must not be a built-in account in order to access the database. Examples of built-in accounts are Local Service and Network Service. Must register as SharePoint Managed Account
SharePoint 2010 Service Account References for Least-Privileged Installation | Nik Patel
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