aa363691_leged_Installation___Nik_Patel__2
[0] Search Service Crawl Rule Content Access Account(e.g. sp_search_crawl) [1] Configured to access content by using the Search administration crawl rules feature. This type of account is optional and can be configured when you create a new crawl rule to override the default content access account configured at the Service Application level [3] None [4] None [5] This account will be assigned to the db_owner role for the associated search service application databases (e.g. Search DB, Crawl DB, and Property DB) during search crawl [2] 
Must be a domain user account and it must have read access to external or secure content sources that you want to crawl by using this account. For SharePoint Server sites that are not part of the server farm and cross-farm scenarios, this account must be explicitly granted full read permissions to the Web applications that host the sites from the central administration. Must not be a member of the farm administrators group. No need to register as SharePoint Managed Account.
SharePoint 2010 Service Account References for Least-Privileged Installation | Nik Patel
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