Roaming profile

A roaming user profile is a concept in the Windows NT family of operating systems that allows users with a computer joined to a Windows Server domain to log on to any computer on the same network and access their documents and have a consistent desktop experience, such as applications remembering toolbar positions and preferences, or the desktop appearance staying the same.

All Windows operating systems since Windows NT 3.1 are designed to support roaming profiles. Normally, a standalone computer stores the user's documents, desktop items, application preferences, and desktop appearance on the local computer in two divided sections, consisting of the portion that could roam plus an additional temporary portion containing items such as the web browser cache. The Windows registry is similarly divided to support roaming; there are System and Local Machine hives that stay on the local computer, plus a separate User hive (HKEY CURRENT USER) designed to be able to roam with the user profile.

When a roaming user is created, the user's profile information is instead stored on a centralized file server accessible from any network-joined desktop computer. The login prompt on the local computer checks to see if the user exists in the domain rather than on the local computer; no pre-existing account is required on the local computer. If the domain login is successful, the roaming profile is copied from the central file server to the desktop computer, and a local account is created for the user.

When the user logs off from the desktop computer, the user's roaming profile is merged from the local computer back to the central file server, not including the temporary local profile items. Because this is a merge and not a move/delete, the user's profile information remains on the local computer in addition to being merged to the network.

When the user logs in on a second desktop computer, this process repeats, merging the roaming profile from the server to the second desktop computer, and then merging back from the desktop to the server when the user logs off.

When the user returns to the first desktop computer and logs in, the roaming profile is merged with the previous profile information, replacing it. If profile caching is enabled, the server is capable of merging only the newest files to the local computer, reusing the existing local files that have not changed since the last login, and thereby speeding up the login process.

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Wikipedia