R

Red Hat

Well-known company that produces distributions of Linux. See also SUSE Linux and Debian.

redirect

To send the output of a command into a particular file. This also works the other way around: the contents of a particular file can be directed into a command. Redirection is achieved within the shell using the left and right angle brackets (< and >), respectively.

regex

See regular expression.

regular expression

Powerful and complex method of describing a search string, usually when searching with tools such as grep (although regular expressions are also used when programming). Regular expressions use various symbols as substitutes for characters or to indicate patterns.

remote

Indicates a computer or service that is available across a network, including but not limited to computers on the Internet (as opposed to local).

root

(1) The bottom of the Linux file system directory structure, usually indicated by a forward slash (/).

(2) The user on a Unix system who has control over all aspects of hardware, software, and the file system.

(3) Used to describe a user who temporarily takes on the powers of the root user (via the sudo command, for example).

RPM

Red Hat Package Manager; system used to install and administer programs. An RPM file, which has an .rpm extension, contains either the binary executable files that make up the program or the source code. In addition, it contains several scripts that check the operating system for compatibility, such as whether you have the correct dependencies, and installs the files on the hard disk.

RTFM

Read the f***ing manual/man page; exclamation frequently used online when a newbie asks for help without having undertaken basic research.

run level

Describes the current operational mode of Linux (typically what services are running). Run level 3 is text-only, although a GUI can be started manually. Run level 5 has a GUI started as part of the boot procedure. Run level 1 is single-user mode (a stripped-down system with minimal running services). Run level 6 is reboot mode; switching to it will cause the computer to terminate its processes and then reboot.