How to change the SQL Server service account

Most entry level DBAs still have the confusion on what is a service account and which is the best to be used and when. This article will take you through that.
Depending on the selection that you made while installing SQL Server, you will have the services installed in your server.

More refer: http://msdn.microsoft.com/en-us/library/ms143504%28v=SQL.105%29.aspx#Use_startup_accounts

SQL Server Database Services: The service for the SQL Server relational Database Engine

SQL Server Agent: Executes jobs, monitors SQL Server, fires alerts, and enables automation of some administrative tasks.
Analysis Services: Provides online analytical processing (OLAP) and data mining functionality for business intelligence applications.
Reporting Services: Manages, executes, creates, schedules, and delivers reports.
Integration Services: Provides management support for Integration Services package storage and execution.
SQL Server Browser: The name resolution service that provides SQL Server connection information for client computers.
Full-text search: Quickly creates full-text indexes on content and properties of structured and semistructured data to provide document filtering and word-breaking for SQL Server.
SQL Server Active Directory Helper: Publishes and manages SQL Server services in Active Directory.
SQL Writer: Allows backup and restore applications to operate in the Volume Shadow Copy Service (VSS) framework.

You can configure you SQL Server related services either during the setup or after the installation using the SQL Server configuration Manager.

Types of startup accounts:

Local User Account: This user account is created in your server where SQL Server is installed, this account does not have access to network resources.

Local Service Account: This is a builtin windows account that is available for configuring services in windows. This account has permissions as same as accounts that are in the users group, thus it has limited access to the resources in the server. This account is not supported for SQL SERVER and AGENT services.

Local System Account: This is a builtin windows account that is available for configuring services in windows. This is a highly privileged account that has access to all resources in the server with administrator rights.

Network Service Account: This is a builtin windows account that is available for configuring services in windows. This has permissions to access resources in the network under the computer account.

Domain Account: This account is a part of your domain that has access to network resources for which it is intended to have permission for. It is always advised to run SQL Server and related services under a domain account with minimum privilege need to run SQL Server and its related services.

Where can you see the Local System, Local Service and Network Service accounts? These are windows in-built accounts that are part of the operating system and assigned to the users, you cannot use the account to login to the system, these accounts are meant to be used for securing and authentication mechanism.

Changing Service Accounts:
As mentioned above, SQL Server service accounts can be configured either during installation or using SQL Server configuration Manager. The first one is part of the installation and can be configured during the step Instance Configuration. I would walk you through changing a service account using SQL Server Configuration Manager.

1. Start -> Programs Microsoft SQL Server 2008 -> Configuration Tools -> SQL Configuration Manager

Open those and then pick the SQL Server Configuration Manager.

You might get a UAC message asking if you want to make changes to the system, and say yes. This application can change service accounts, which is a sysadmin function. The screen basically looks like this:

2. Highlight a service in the right pane, right click for properties.

You can change the built-in account here, else if you would like to change it to a Local User account or a domain user account, choose option This Account to Ungray it and enter the credentials of a local or a domain user account.

If you right click the SQL Server entry, the database engine, you can select the properties, and you’ll get this screen:

On this screen, you can change the service account, and this is where you should change it. There are the three built in accounts in the top drop down (Local System, Local Service, and Network Service). I don’t recommend these. Instead, I recommend you create a new Active Directory Domain account (or local user account), assign it no rights, and then use the lower radio button to select the account.

Note that you do can search for it, and also you need to enter the user account. The password, while conforming to your domain policy, shouldn’t be one you use elsewhere. Make it a long, impossible to guess combination of stuff. You don’t need to recover this or log on as the user after you’ve assigned it to SQL Server. If you need to recover the password, just change it.
A couple quick notes, on the Service Tab you can set the startup mode (Manual, automatic) for the database engine.

You can also change startup parameters here, on the Advanced tab.

That’s it, it’s easy, and it’s how you should change the service account for SQL Server.

Remember that you will need to restart the SQL Server and related services for the new Service account to take effect.

Tip: If you have no domain accounts or running under multiple domains and Your SQL Server needs access to other resources in the network, you can create an user account with same username and password across all Servers and use that as service account in your servers.

Refer to http://www.sqlservercentral.com/blogs/steve_jones/2011/12/15/how-to-change-the-sql-server-service-cccount/