For every computer running Windows NT, Windows 2000 Professional, or Windows XP and every server running Windows Server 2003 that is a member of a domain, a computer account must be created in the domain. The computer account is a security principal, and it can be authenticated and granted permissions to access resources. A computer account is automatically created for each computer running the listed operating systems when the computer joins the domain. Note: No Account No computer accounts are created for computers running any version of Windows 95, Windows 98, or Windows Me. They lack the advanced security features that make the computer accounts worthwhile. This is an important factmost network administrators prefer to have no computers running these operating systems in their networks because it is difficult to manage and secure these computers. Although it is true that computer accounts are created automatically when a computer joins a domain, sometimes it is worthwhile to create computer accounts manually. Doing so allows a user to install a new computer in the appropriate location in the domain, even if that user doesn't have the necessary administrative privileges, using the name of the computer account that already exists. Note that even if the computer object has been precreated, the user installing the computer must have been delegated the right to join a computer to the domain. Creating Computer Accounts Using the Active Directory Users and Computers ConsoleTo create a computer account using Active Directory Users and Computers, right-click the container you want the account to appear in and then choose New, Computer from the context menu. Assign the necessary values to the parameters available and click OK. Figure 2.26 shows the New Object dialog box in which you type the computer name and give a preWindows 2000 computer name (limited to 15 characters). You may also designate the computer as a preWindows 2000 computer, and you may state that the computer is to be a Windows NT 4 backup domain controller. Figure 2.26. Type the name of the computer. Windows Server 2003 will automatically create a preWindows 2000 computer name. Creating Computer Accounts by Joining the DomainThe easiest way to add a computer account to a domain is from the computer that you want to add. To create a computer account by joining a domain, follow the procedure in Step by Step 2.6.
After a short pause, a dialog box will appear to welcome the computer to the domain. The computer must be rebooted so that it can come up as a member of the domain. After the computer is a member of the domain, a user logging on to the domain has the logon request passed by the workstation through a secure channel to the domain controller. The computer must have a domain computer account for the secure channel to be created.
Troubleshooting Computer AccountsBecause computers need to authenticate to one another, they need accounts and passwords. In addition to the two methods described previously, a computer account is also created when a Windows Server 2003 server is promoted to a domain controller with dcpromo. Like user accounts, each computer account has a password. Passwords are created by the process that creates a computer account. On a defined interval, a process running on the local computer changes the password automatically, and the new password is communicated securely to a domain controller in the computer's domain. What happens if, at the time a server running Windows Server 2003 changes its password, there is no domain controller available for the new password to be written to? The next time the two computers are able to communicate, the server with the changed password, on finding that the new password is not accepted, uses the previous one instead. After authentication is complete with the old password, the new password is stored on the domain controller and is subsequently replicated to all domain controllers in the domain. Troubleshooting Issues Related to Computer Accounts by Using the Active Directory Users and Computers Console
Reset accountsWhen a computer account is operating incorrectly, it may be impossible to log on to the domain from the computer. You can see how, if the computer cannot authenticate to the domain controller, it will be impossible for the user to log on. In this case it is necessary to reset the computer's account and rejoin the computer to the domain. This process reestablishes the secure relationship between the computer and the domain it is a member of. To reset a computer's account using Active Directory Users and Computers, select the folder containing the computer account and right-click the computer object. Choose Reset Account from the context menu, and click Yes from the confirmation dialog box. Reboot the workstation and then rejoin the domain as described earlier. To reset a computer's account from the command line, you use the dsmod command with the -reset switch: dsmod computer <dn of computer> -reset As in the case where the computer account was reset using Active Directory Users and Computers, you will have to rejoin the computer to the domain.
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