Linux/Unix

Linux and UNIX both have two tier security, which limits any system-wide changes to the root user, a special user account on all UNIX-like systems. While the root user has virtually unlimited permission to effect system changes, programs running as a regular user are limited in where they can save files, what hardware they can access, etc. In many systems, a user's memory usage, their selection of available programs, their total disk usage or quota, available range of programs' priority settings, and other functions can also be locked down. This provides the user with plenty of freedom to do what needs to be done, without being able to put any part of the system in jeopardy (barring accidental triggering of system-level bugs) or make sweeping, system-wide changes. The user's settings are stored in an area of the computer's file system called the user's home directory, which is also provided as a location where the user may store their work, a concept later adopted by Windows as the 'My Documents' folder. Should a user have to install software outside of his home directory or make system-wide changes, they must become the root user temporarily, usually with the su or sudo command, which is answered with the computer's root password when prompted. Some systems (such as Ubuntu and its derivatives) are configured by default to allow select users to run programs as the root user via the sudo command, using the user's own password for authentication instead of the system's root password. One is sometimes said to "go root" or "drop to root" when elevating oneself to root access.