Safe Mode
Encyclopedia
Safe mode is a diagnostic mode
of a computer operating system
(OS). It can also refer to a mode of operation by application software
. Safe mode is intended to fix most, if not all problems within an operating system. It is also widely used for removing Rogue security software.
and Mac OS X
are examples of contemporary operating systems that implement a safe mode (called "Safe Boot" in Mac OS X); 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 also 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.
Microsoft Windows' safe mode is accessed by pressing the F8 key
as the operating system boots. 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 and which allows an administrative account commonly known as "root" to have its password reset without knowing what it is first. 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 activates Safe Boot that has background maintenance features (Besides the mode selection, it runs a file system repair, and in Mac OS 10.4, it disables all fonts other than those in /System/Library/Fonts, moves to the Trash all font caches normally stored in /Library/Caches/com.apple.ATS/(uid)/, where (uid) is a user ID number such as 501, and disables all startup items and any Login Items) and can reset an administrative accounts' password. In Windows, safe mode with networking, one of the variations of safe mode, can be used to troubleshoot network issues. In OS X, Safe Boot always includes networking.
sometimes offers a safe mode as well. In the PHP
interpreter
, prior to version 6, safe mode offers stricter security measures. 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.
Diagnosis
Diagnosis is the identification of the nature and cause of anything. Diagnosis is used in many different disciplines with variations in the use of logics, analytics, and experience to determine the cause and effect relationships...
of a computer 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...
(OS). It can also refer to a mode of operation by application software
Application software
Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...
. Safe mode is intended to fix most, if not all problems within an operating system. It is also widely used for removing Rogue security software.
Operating system safe mode
Microsoft WindowsMicrosoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
and 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...
are examples of contemporary operating systems that implement a safe mode (called "Safe Boot" in Mac OS X); as well as other complex electronic devices
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
.
An 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...
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
Booting
In computing, booting is a process that begins when a user turns on a computer system and prepares the computer to perform its normal operations. On modern computers, this typically involves loading and starting an operating system. The boot sequence is the initial set of operations that the...
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 also choose to boot to the Recovery Console
Recovery Console
The Recovery Console is a feature of the Windows 2000, Windows XP and Windows Server 2003 operating systems. It provides the means for administrators to perform a limited range of tasks using a command line interface. Its primary function is to enable administrators to recover from situations...
, 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.
Microsoft Windows' safe mode is accessed by pressing the F8 key
Function key
A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions...
as the operating system boots. 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
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating systems is single-user mode
Runlevel
The term runlevel refers to a mode of operation in one of the computer operating systems that implement Unix System V-style initialization. Conventionally, seven runlevels exist, numbered from zero to six; though up to ten, from zero to nine, may be used. S is sometimes used as a synonym for one...
, in which daemons
Daemon (computer software)
In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...
and the 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...
are not started, and only the root user can log in and which allows an administrative account commonly known as "root" to have its password reset without knowing what it is first. On Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
versions 6, 7, 8 and 9, a similar mode is achieved by holding down the shift key
Shift key
The shift key is a modifier key on a keyboard, used to type capital letters and other alternate "upper" characters. There are typically two shift keys, on the left and right sides of the row below the home row...
while booting, which starts the system without extensions
Extension (Mac OS)
On the Apple Macintosh operating system prior to Mac OS X, extensions were small pieces of code that extended the system's functionality. They were run initially at start-up time, and operated by a variety of mechanisms, including trap patching and other code modifying techniques. Initially an...
. In 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...
holding the shift key after powering up activates Safe Boot that has background maintenance features (Besides the mode selection, it runs a file system repair, and in Mac OS 10.4, it disables all fonts other than those in /System/Library/Fonts, moves to the Trash all font caches normally stored in /Library/Caches/com.apple.ATS/(uid)/, where (uid) is a user ID number such as 501, and disables all startup items and any Login Items) and can reset an administrative accounts' password. In Windows, safe mode with networking, one of the variations of safe mode, can be used to troubleshoot network issues. In OS X, Safe Boot always includes networking.
Application software safe mode
Application softwareApplication software
Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...
sometimes offers a safe mode as well. In the PHP
PHP
PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...
interpreter
Interpreter (computing)
In computer science, an interpreter normally means a computer program that executes, i.e. performs, instructions written in a programming language...
, prior to version 6, safe mode offers stricter security measures. Mozilla Firefox
Mozilla Firefox
Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. , Firefox is the second most widely used browser, with approximately 25% of worldwide usage share of web browsers...
's safe mode allows the user to remove extensions which may be preventing the browser from loading. Internet Explorer
Internet Explorer
Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...
can run in "No Add-Ons" mode and Protected Mode.
External links
- More information about Safe-mode from SymantecSymantecSymantec Corporation is the largest maker of security software for computers. The company is headquartered in Mountain View, California, and is a Fortune 500 company and a member of the S&P 500 stock market index.-History:...
. - In Windows, what is 'Safe Mode' used for and why? (about win9x systems)
- How to Start Windows XP in Safe Mode
- Mac OS X: Starting up in Safe Mode
- http://www.debuntu.org/recover-root-password-single-user-mode-and-grub
- http://hints.macworld.com/article.php?story=20080414140636495