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In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of the account is not the determining factor; on Unix-like systems, for example, the user with a user identifier (UID) of zero is the superuser, regardless of the name of that account; and in systems which implement a role based security model, any user with the role of superuser (or its synonyms) can carry out all actions of the superuser account. The
principle of least privilege In information security, computer science, and other fields, the principle of least privilege (PoLP), also known as the principle of minimal privilege (PoMP) or the principle of least authority (PoLA), requires that in a particular abstraction la ...
recommends that most users and applications run under an ordinary account to perform their work, as a superuser account is capable of making unrestricted, potentially adverse, system-wide changes.


Unix and Unix-like

In
Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
computer OSes (such as
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...
), ''root'' is the conventional name of the user who has all rights or permissions (to all files and programs) in all modes (single- or multi-user). Alternative names include ''baron'' in BeOS and ''avatar'' on some Unix variants. BSD often provides a ''toor'' ("root" written backward) account in addition to a root account. Regardless of the name, the superuser always has a
user ID Unix-like operating systems identify a user by a value called a user identifier, often abbreviated to user ID or UID. The UID, along with the group identifier (GID) and other access control criteria, is used to determine which system resources a u ...
of 0. The root user can do many things an ordinary user cannot, such as changing the ownership of files and binding to network ports numbered below 1024. The name ''root'' may have originated because ''root'' is the only user account with permission to modify the root directory of a Unix system. This directory was originally considered to be root's home directory, but the UNIX Filesystem Hierarchy Standard now recommends that root's home be at .' The first process bootstrapped in a
Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
system, usually called , runs with root privileges. It spawns all other processes directly or indirectly, which inherit their parents' privileges. Only a process running as root is allowed to change its user ID to that of another user; once it has done so, there is no way back. Doing so is sometimes called ''dropping root privileges'' and is often done as a security measure to limit the damage from possible contamination of the process. Another case is and other programs that ask users for credentials and in case of successful authentication allow them to run programs with privileges of their accounts. It is often recommended that ''root'' is never used as a normal user account, since simple
typographical errors A typographical error (often shortened to typo), also called a misprint, is a mistake (such as a spelling mistake) made in the typing of printed (or electronic) material. Historically, this referred to mistakes in manual type-setting (typography). ...
in entering commands can cause major damage to the system. Instead, a normal user account should be used, and then either the (substitute user) or (substitute user do) command is used. The approach requires the user to know the root password, while the method requires that the user be set up with the power to run "as root" within the file, typically indirectly by being made a member of the ''wheel'', ''adm'', ''admin'', or ''sudo'' group. For a number of reasons, the approach is now generally preferred – for example it leaves an audit trail of who has used the command and what administrative operations they performed. Some OSes, such as
macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...
and some
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...
distributions (most notably Ubuntu), automatically give the initial user created the ability to run as root via – but this is configured to ask them for their password before doing administrative actions. In some cases the actual ''root'' account is disabled by default, so it can't be directly used. In mobile platform-oriented OSs such as
Apple iOS iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that powers many of the company's mobile devices, including the iPhone; the term also includes ...
and Android, superuser access is inaccessible by design, but generally the security system can be exploited in order to obtain it. In a few systems, such as Plan 9, there is no superuser at all.


Microsoft Windows

In Windows NT and later systems derived from it (such as Windows 2000,
Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was release to manufacturing, released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Wind ...
, Windows Server 2003, and Windows Vista/ 7/ 8/ 10/ 11), there must be at least one administrator account (Windows XP and earlier) or one able to elevate privileges to superuser (Windows Vista/7/8/10/11 via
User Account Control User Account Control (UAC) is a mandatory access control enforcement feature introduced with Microsoft's Windows Vista and Windows Server 2008 operating systems, with a more relaxed
). In Windows XP and earlier systems, there is a built-in administrator account that remains hidden when a user administrator-equivalent account exists. This built-in administrator account is created with a blank password. This poses security risks as local users would be able to access the computer via the built-in administrator account if the password is left blank, so the account is disabled by default in Windows Vista and later systems due to the introduction of User Account Control (UAC). Remote users are unable to access the built-in administrator account. A Windows administrator account is not an exact analogue of the
Unix Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, ...
root account – Administrator, the built-in administrator account, and a user administrator account have the same level of privileges. The default user account created in Windows systems is an administrator account. Unlike macOS, Linux, and Windows Vista/7/8/10 administrator accounts, administrator accounts in Windows systems without UAC do not insulate the system from most of the pitfalls of full root access. One of these pitfalls includes decreased resilience to malware infections. To avoid this and maintain optimal system security on pre-UAC Windows systems, it is recommended to simply authenticate when necessary from a standard user account, either via a password set to the built-in administrator account, or another administrator account. In Windows Vista/7/8/10/11 administrator accounts, a prompt will appear to authenticate running a process with elevated privileges. Usually, no user credentials are required to authenticate the UAC prompt in administrator accounts but authenticating the UAC prompt requires entering the username and password of an administrator in standard user accounts. In Windows XP (and earlier systems) administrator accounts, authentication is not required to run a process with elevated privileges and this poses another security risk that led to the development of UAC. Users can set a process to run with elevated privileges from standard accounts by setting the process to "run as administrator" or using the command and authenticating the prompt with credentials (username and password) of an administrator account. Much of the benefit of authenticating from a standard account is negated if the administrator account's credentials being used has a blank password (as in the built-in administrator account in Windows XP and earlier systems), hence why it is recommended to set a password for the built-in administrator account. In Windows NT, 2000 and higher, the root user is the Administrator account.


Novell NetWare

In Novell NetWare, the superuser was called "supervisor","Supervisor (Bindery) User Created on Every NetWare 4 Server"
01 Feb 1996, novell.com
later "admin".


OpenVMS

In OpenVMS, "SYSTEM" is the superuser account for the OS.


Older personal systems

On many older OSes on computers intended for personal and home use, anyone using the system had full privileges. Many such systems, such as DOS, did not have the concept of multiple accounts, and although others such as Windows 95 did allow multiple accounts, this was only so that each could have its own preferences profile – all users still had full administrative control over the machine.


See also

* Jailbreaking (iOS) *
nobody (username) {{lowercase In many Unix variants, "nobody" is the conventional name of a user identifier which owns no files, is in no privileged groups, and has no abilities except those which every other user has. It is normally not enabled as a user account ...
* passwd *
Power user A power user is a user of computers, software and other electronic devices, who uses advanced features of computer hardware, operating systems, programs, or websites which are not used by the average user. A power user might not have extensive tec ...
* Privilege escalation * Rooting (Android OS) * Rootkit *
sudo sudo ( or ) is a program for Unix-like computer operating systems that enables users to run programs with the security privileges of another user, by default the superuser. It originally stood for "superuser do", as that was all it did, and it ...


References


External links

{{Wiktionary
root Definition
– by The Linux Information Project (LINFO)

System administration Operating system security