Fast user switching
Encyclopedia
Fast user switching is a feature on some modern multi-user
operating system
s such as Windows XP
and newer, Mac OS X
, Linux
. It allows users to switch between user accounts on a single PC
without quitting applications and logging out. Analogous functionality was first developed on consumer level hardware by the Xenix
operating system which supported multiple virtual consoles. Linux
, BSD, and most other PC Unixes adopted virtual terminals and further developed the user interfaces, including allowing users to optionally run separate graphical X Window System
sessions.
Many free software
environments, such as GNOME
or KDE
, support fast user switching with a drop menu, in a way analogous to OS X. For installations with older environments, the functionality must be enabled in the configuration file of the X display manager (for example GDM
) then a hot key sequence such as
Fast user switching may potentially introduce various security-related complications, and is handled differently among operating systems, each having its advantages and disadvantages. One possibility, simple and secure, is that only the first user gets ownership of resources. A second option is to grant ownership of resources to each new user. The last one to log in takes ownership. A third is to allow all users access to shared resources. This is easier and more intuitive, but allows (for example) one user to record another user's conversation. In Windows, shared resources, such as sound, are available to all sessions. In Red Hat Linux
, the default behavior is to give ownership of "console resources" to the first connected session, but it can share resources among groups of console users or be configured to manage console ownership differently.
which is a component of Winlogon
, and with which fast user switching interacts, can be programmatically called to automate a fast user switch. A Powertoy
known as Super fast user switcher was offered in 2002 by Microsoft. It allowed fast user switching using a keyboard hotkey (Win+Q) (similar to Alt-Tab
) without even going to the Welcome screen. It was later made unavailable when the original set of powertoys was replaced by updated versions but still works with Windows XP SP3 (32-bit) when running as administrator.
In Windows Vista, GINA is replaced by Credential Providers, however they do not support programmatic initiation of fast user switching.
In Windows XP, fast user switching was unavailable if the computer is on a Windows Server domain
network or if Offline Files was enabled. Windows Vista
and later no longer have these restrictions.
Multi-user
Multi-user is a term that defines an operating system or application software that allows concurrent access by multiple users of a computer. Time-sharing systems are multi-user systems. Most batch processing systems for mainframe computers may also be considered "multi-user", to avoid leaving the...
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s such as Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
and newer, Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
, Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
. It allows users to switch between user accounts on a single PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
without quitting applications and logging out. Analogous functionality was first developed on consumer level hardware by the Xenix
Xenix
Xenix is a version of the Unix operating system, licensed to Microsoft from AT&T in the late 1970s. The Santa Cruz Operation later acquired exclusive rights to the software, and eventually superseded it with SCO UNIX ....
operating system which supported multiple virtual consoles. Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, BSD, and most other PC Unixes adopted virtual terminals and further developed the user interfaces, including allowing users to optionally run separate graphical X Window System
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
sessions.
Many free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
environments, such as GNOME
GNOME
GNOME is a desktop environment and graphical user interface that runs on top of a computer operating system. It is composed entirely of free and open source software...
or KDE
KDE
KDE is an international free software community producing an integrated set of cross-platform applications designed to run on Linux, FreeBSD, Microsoft Windows, Solaris and Mac OS X systems...
, support fast user switching with a drop menu, in a way analogous to OS X. For installations with older environments, the functionality must be enabled in the configuration file of the X display manager (for example GDM
GNOME Display Manager
GDM provides a simpler to use alternative display manager for the X Window System's XDM.The X Window System by default uses the XDM display manager. However, resolving XDM configuration issues typically involves editing a configuration file. GDM allows users to customize or troubleshoot settings...
) then a hot key sequence such as
CTRL-ALT-F8 is pressed. A separate login window will now appear and the second user can login (or even the first user again). Alternatively, in the default install, new X sessions can be started at will by using different display parameters to have them run in different virtual terminals (e.g. "startx -- :1" or "X :1 -query localhost"). Again, hot key sequences allow the user switching to take place.Fast user switching may potentially introduce various security-related complications, and is handled differently among operating systems, each having its advantages and disadvantages. One possibility, simple and secure, is that only the first user gets ownership of resources. A second option is to grant ownership of resources to each new user. The last one to log in takes ownership. A third is to allow all users access to shared resources. This is easier and more intuitive, but allows (for example) one user to record another user's conversation. In Windows, shared resources, such as sound, are available to all sessions. In Red Hat Linux
Red Hat Linux
Red Hat Linux, assembled by the company Red Hat, was a popular Linux based operating system until its discontinuation in 2004.Red Hat Linux 1.0 was released on November 3, 1994...
, the default behavior is to give ownership of "console resources" to the first connected session, but it can share resources among groups of console users or be configured to manage console ownership differently.
Windows implementation
Fast user switching in Windows is based on Remote Desktop Services technology. In Windows XP, GINAGraphical identification and authentication
The graphical identification and authentication library is a component of some Microsoft Windows operating systems that provides secure authentication and interactive logon services....
which is a component of Winlogon
Winlogon
In computing, Winlogon is the component of Microsoft Windows operating systems that is responsible for handling the secure attention sequence, loading the user profile on logon, and optionally locking the computer when a screensaver is running...
, and with which fast user switching interacts, can be programmatically called to automate a fast user switch. A Powertoy
Microsoft PowerToys
Microsoft PowerToys is a set of programs provided by Microsoft for the Windows operating system. PowerToys are not integrated into Windows since they are released after the public release of a Windows operating system...
known as Super fast user switcher was offered in 2002 by Microsoft. It allowed fast user switching using a keyboard hotkey (Win+Q) (similar to Alt-Tab
Alt-Tab
' is the common name for a keyboard shortcut that has been in Microsoft Windows since Windows 3.0. This shortcut switches between top-level windows without using the mouse; hence it was named Task Switcher ....
) without even going to the Welcome screen. It was later made unavailable when the original set of powertoys was replaced by updated versions but still works with Windows XP SP3 (32-bit) when running as administrator.
In Windows Vista, GINA is replaced by Credential Providers, however they do not support programmatic initiation of fast user switching.
In Windows XP, fast user switching was unavailable if the computer is on a Windows Server domain
Windows Server domain
A Windows domain is a collection of security principals that share a central directory database. This central database contains the user accounts and security information for...
network or if Offline Files was enabled. Windows Vista
Windows Vista
Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
and later no longer have these restrictions.