Safe mode

Safe mode usually refers to a diagnostic mode used by a computer operating system (OS). It can also refer to a mode of operation by application software.

Operating System safe mode

Microsoft Windows and Mac OS X are examples of contemporary operating systems that implement a safe mode; as well as other complex electronic devices.

An operating system in safe mode will have reduced functionality, but the task of isolating problems is easier because many non-core components are disabled (turned off). An installation that will only boot into its safe mode typically has a major problem, such as disk corruption or the installation of poorly configured software that prevents the operating system from successfully booting into its normal operating mode.

Though it varies by operating system, typically safe mode loads as few executable modules as possible and usually disables devices, except for the minimum necessary to display information and accept input. Safe mode can also take the form of a parallel "miniature" operating system that has no configuration information shared with the normal operating system. For example, on Microsoft Windows, the user can choose to boot to the Recovery Console, a small text-based troubleshooting mode kept separate from the main operating system (and can also be accessed by booting the install CD), or to various "safe mode" options that run the dysfunctional operating system, but with features such as video drivers, audio and networking disabled.

Safe mode typically provides access to utility and diagnostic programs so a user can troubleshoot what is preventing the operating system from working normally. Safe mode is intended for maintenance, not functionality, and provides minimal access to features which often frustrates users who are only aware that their computer "isn't working right".

Safe mode is a troubleshooting method on most electronic devices, including mobile phones and even NASA spacecraftcite web |url=http://www.physorg.com/news2683.html |title=Deep Impact is out of 'safe mode' |date=14 January 2005 |publisher=PhysOrg.com |accessdate=2006-10-07] which often run VxWorks.

Microsoft Windows' safe mode is accessed by repeatedly pressing the F8 key as the operating system boots. [ [http://support.microsoft.com/kb/315222 A description of the Safe Mode Boot options in Windows XP] ] Also, in a multi-boot environment with multiple versions of Windows installed side by side, the F8 key can be pressed at the OS selector prompt to get to safe mode.

An equivalently minimal setting in Unix-like operating systems is single-user mode, in which daemons and the X Window System are not started, and only the root user can log in. On Mac OS versions 6, 7, 8 and 9, a similar mode is achieved by holding down the shift key while booting, which starts the system without extensions. In Mac OS X holding the shift key after powering up puts the system in safe mode. Safe mode with networking, one of the variations of safe mode, can be used to troubleshoot network issues.

Application software safe mode

Application software sometimes offers a safe mode as well. In the PHP interpreter, prior to version 6, safe mode offers stricter security measures. [ [http://uk.php.net/features.safe-mode Safe mode in PHP] ] Mozilla Firefox's safe mode allows the user to remove extensions which may be preventing the browser from loading. Internet Explorer can run in "No Add-Ons" mode and Protected Mode.

References

External links

* [http://service1.symantec.com/SUPPORT/tsgeninfo.nsf/docid/2001052409420406?OpenDocument More information about Safe-mode] from Symantec.
* [http://computer.howstuffworks.com/question575.htm In Windows, what is 'Safe Mode' used for and why?]
* [http://www.computerhope.com/issues/chsafe.htm Getting into Windows Safe Mode.]
* [http://guino.home.insightbb.com/nosafefaq.html Prevent access and Disable Safe Mode in Windows.]