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The Unix command su, which stands for 'substitute user' [1] [2] (or historically 'superuser' [3] [4]), is used by a computer user to execute commands with the privileges of another user account. When executed it invokes a shell without changing the current working directory or the user environment.
Version 2 AT&T UNIX tabs: Misc Mandatory Set terminal tabs PWB UNIX tail: Text processing Mandatory Copy the last part of a file PWB UNIX [citation needed] talk: Misc Optional (UP) Talk to another user 4.2BSD tee: Shell programming Mandatory Duplicate the standard output: Version 5 AT&T UNIX test: Shell programming Mandatory Evaluate expression
The test command in Unix evaluates the expression parameter. In most recent shell implementations, it is a shell builtin, even though the external version still exists.In the second form of the command, the [ ] (brackets) must be surrounded by blank spaces (this is because [is a program and POSIX compatible shells require a space between the program name and its arguments).
The Linux console is a system console internal to the Linux kernel. A system console is the device which receives all kernel messages and warnings and which allows logins in single user mode. [1] The Linux console provides a way for the kernel and other processes to send text output to the user, and to receive text input from the user.
After authentication, and if the configuration file permits the user access, the system invokes the requested command. sudo retains the user's invocation rights through a grace period (typically 5 minutes) per pseudo terminal, allowing the user to execute several successive commands as the requested user without having to provide a password again.
A chmod command first appeared in AT&T Unix version 1, along with the chmod system call. As systems grew in number and types of users, access-control lists [3] were added to many file systems in addition to these most basic modes to increase flexibility. The version of chmod bundled in GNU coreutils was written by David MacKenzie and Jim ...
Modern Unix systems generally use user groups as a security protocol to control access privileges. The wheel group is a special user group used on some Unix systems, mostly BSD systems, [citation needed] to control access to the su [4] [5] or sudo command, which allows a user to masquerade as another user (usually the super user).
The Unix and Linux access rights flags setuid and setgid (short for set user identity and set group identity) [1] allow users to run an executable with the file system permissions of the executable's owner or group respectively and to change behaviour in directories. They are often used to allow users on a computer system to run programs with ...