Fast user switching is a feature of a
multi-user
Multi-user software is computer software that allows 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 leavi ...
operating system
An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ...
which allows users to switch between
user accounts without quitting applications and logging out.
In Linux
The Linux kernel's VT subsystem dates back to 1993 and does not understand the concept of multiple "seats", meaning that of up to 63 VTs, only one VT can be active at any given time. Despite this kernel limitation,
multi-seat is supported on
Linux
Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
. The feature of "fast user switching" has less severe necessities than multi-seat does because the multiple users are not working simultaneously.
The most straight forward solution to elegant multi-seat are
kmscon/
systemd-consoled in combination with
systemd-logind. The available
desktop environments such as
GNOME or
KDE Software Compilation adapt their graphical login and session manager (e.g.
GDM,
SDDM,
LightDM, etc.) to the underneath solution and have to be configured to implement fast user switching that way.
For installations with older environments, the functionality must be enabled in the appropriate configuration files then a
hot key sequence such as
CTRL-ALT-F8 is pressed. A separate login window will now appear and the second user can log in (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, 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.
In macOS
Fast user switching was introduced in 2003 with
Mac OS X Panther.
In Microsoft Windows
Fast user switching in Windows is based on
Remote Desktop Services technology. In Windows XP,
GINA 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
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...
and later no longer have these restrictions.
The Windows Vista and Windows Server 2008 Developer Story: Application Compatibility Cookbook
/ref> Fast user switching is also not available on Windows XP if SerialKeys (an accessibility option that allows users to use speech augmentation devices) or Client Services for NetWare are installed.
See also
* Time-sharing
In computing, time-sharing is the Concurrency (computer science), concurrent sharing of a computing resource among many tasks or users by giving each Process (computing), task or User (computing), user a small slice of CPU time, processing time. ...
* Multiseat configuration
References
{{reflist
External links
Architecture of Fast User Switching in Windows XP
Operating system technology
Windows components
Windows administration
MacOS administration
Linux user management and support-related utilities
Linux authentication-related software
MacOS user interface