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init (short for "initialization") is the program on Unix and Unix-like systems that spawns all other processes. It runs as a daemon and typically has PID 1. Initialization may refer to: Booting, a process that starts computer operating systems Initialism, an abbreviation formed using the initial letters of words or word parts In counterstrike :source, Initialize is a maddy that is better than u ) Category: ...
Filiation of Unix and Unix-like systems Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy. ...
Diagram of the relationships between several Unix-like systems 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. ...
In Unix and other computer multitasking operating systems, a daemon is a computer program that runs in the background, rather than under the direct control of a user; they are usually instantiated as processes. ...
In computing, the process identifier (normally referred to as the process ID or just PID) is a number used by some operating system kernels (such as that of UNIX or Windows NT) to uniquely identify a process. ...
The functionality diverged, in Unixes such as System III and System V, from the functionality provided by the init in Research Unix and its BSD derivatives. The usage on most Linux distributions is compatible with System V, but some distributions, such as Arch Linux and Slackware, use a BSD-style and others, such as Gentoo Linux, have their own customized version. System III was a version of the Unix operating system released by AT&Ts Unix System Group (USG). ...
It has been suggested that Traditional Unix be merged into this article or section. ...
This article or section is not written in the formal tone expected of an encyclopedia article. ...
Berkeley Software Distribution (BSD, sometimes called Berkeley Unix) is the Unix derivative distributed by the University of California, Berkeley, starting in the 1970s. ...
A Linux distribution, often simply distribution or distro, is a member of the Linux family of Unix-like operating systems comprising the Linux kernel, the non-kernel parts of the GNU operating system, and assorted other software. ...
Arch Linux is a Linux distribution founded by Judd Vinet that emphasizes simplicity. ...
Slackware was one of the earliest Linux distributions, and is the oldest, and most UNIX-like, distribution still being maintained[1]. It was created by Patrick Volkerding of Slackware Linux, Inc. ...
The Gentoo Linux operating system (pronounced ) is a Linux distribution named after the Gentoo penguin. ...
BSD-style BSD init runs the initialization shell script located in '/etc/rc', then launches getty on text-based terminals or a windowing system such as X on graphical terminals. There are no runlevels; the 'rc' file determines how init is to be run. A shell script is a script written for the shell, or command line interpreter, of an operating system. ...
getty is a Unix program running on a host computer that manages physical or virtual terminals. ...
A windowing system is a graphical user interface (GUI) which uses the window as one of its primary metaphors. ...
KDE 3. ...
Advantages: Simple and easy to edit manually.
Problems: If a 3rd-party package needs to have an initialization script run during the boot procedure, it needs to edit one of the existing boot scripts, but a simple mistake in that process could lead to an unbootable system.
Note that modern *BSD variants have long supported a site-specific 'rc.local' file that is run in a sub-shell near the end of the boot sequence to mitigate the risks of making the system unbootable, and later, a local 'rc.d' directory where packages could install their own independent start/stop scripts (usually provided by the ports collection/pkgsrc). FreeBSD and NetBSD now use by default (as of version 5.0 and 1.5, respectively) the rc.d framework where the whole userland boot sequence is fragmented into smaller scripts, similarly to SysV. Berkeley Software Distribution (BSD, sometimes called Berkeley Unix) is the Unix derivative distributed by the University of California, Berkeley starting in the 1970s. ...
Ports collections (or ports trees, or just ports) are the sets of makefiles and patches provided by the BSD-based operating systems, FreeBSD, NetBSD and OpenBSD, as a simple method of installing software or creating binary packages. ...
pkgsrc (package source) is a package management system for Unix-like operating systems. ...
FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4. ...
NetBSD is a freely redistributable, open source version of the Unix-like BSD computer operating system. ...
SysV-style System V init examines the '/etc/inittab' file for an 'initdefault' entry, which tells init whether there is a default runlevel. If there is no default runlevel, then the user is dumped to a system console, where a runlevel must be entered manually. The term runlevel refers to a mode of operation in one of the computer operating systems that implement Unix System V-style initialization. ...
Advantages: Flexibility and scalability.
Problems: Complexity.
Runlevels The Runlevels in System V describe certain states of a machine, characterized by the processes run. There are generally 8 runlevels. These are the runlevels 0 to 6 and S or s, which are aliased to the same runlevel. Of these eight, 3 are so-called "reserved" runlevels: The term runlevel refers to a mode of operation in one of the computer operating systems that implement Unix System V-style initialization. ...
It has been suggested that Traditional Unix be merged into this article or section. ...
- 0. Halt
- 1. Single user mode
- 6. Reboot
Aside from runlevels 0, 1, and 6, every Unix system treats runlevels a little differently. The common denominator is the /etc/inittab file, which defines what each runlevel does (if they do anything at all).
Default runlevels On the two Linux distributions defaulting to runlevel 5 in the table above, runlevel 5 is a multiuser graphical environment running the X Window System, usually with a display manager. However, in the Solaris operating system, runlevel 5 is typically reserved to shutdown and automatically poweroff the machine. AIX (Advanced Interactive eXecutive) is a proprietary operating system developed by IBM based on UNIX System V. Before the product was ever marketed, the acronym AIX originally stood for Advanced IBM UNIX. AIX has pioneered numerous network operating system enhancements, introducing new innovations later adopted by Unix-like operating systems...
Debian, created by the Debian Project, is a widely used distribution of free software developed through the collaboration of volunteers from around the world. ...
The Gentoo Linux operating system (pronounced ) is a Linux distribution named after the Gentoo penguin. ...
Mandriva Linux (formerly Mandrakelinux or Mandrake Linux) is a Linux distribution created by Mandriva (formerly Mandrakesoft). ...
Red Hat Linux was a popular Linux distribution assembled by Red Hat until the early 2000s, when it was discontinued. ...
Fedora Core is an RPM-based Linux distribution, developed by the community-supported Fedora Project and sponsored by Red Hat. ...
Slackware is a Linux distribution. ...
Solaris is a computer operating system developed by Sun Microsystems. ...
SUSE (pronounced , loosely [SOO-zuh] [1] in English) is a major retail Linux distribution, produced in Germany and owned by Novell, Inc. ...
Ubuntu (IPA pronunciation ) is a predominantly desktop-oriented Linux distribution, based on Debian GNU/Linux but with a stronger focus on usability, regular releases, and ease of installation. ...
KDE 3. ...
In computing, in the context of the X Window System, an X display manager keeps the X server process alive on the X server machine, connecting it to a physical screen and serving a login prompt on this screen if no clients have started running there. ...
Solaris is a computer operating system developed by Sun Microsystems. ...
On most systems users can check the current runlevel with either of the following commands:
$ runlevel $ who -r The current runlevel is typically changed by root running the telinit or init commands. The default runlevel is set in the /etc/inittab file with the :initdefault: entry. On many computer operating systems, superuser, or root, is the term used for the special user account that is controlled by the system administrator. ...
Skipping init In Linux systems, with most modern bootloaders (such as LILO or GRUB), users can change which process the kernel spawns at the end of its initialization from the normal default of /sbin/init. This is generally done by typing init=/foo/bar at the bootloader's prompt. Appending init=/bin/bash, for example, will bring up a single root shell, without a password. If the system administrator feels that this is insecure, he may setup a BIOS password (and in the case of GRUB, MD5 hashed boot passwords). In computing, booting is a bootstrapping process that starts operating systems when the user turns on a computer system. ...
LILO (LInux LOader) is a boot loader for Linux developed by John Coffman. ...
Grub or GRUB can mean: a slang term for food a beetle larva that resembles a worm a distributed commercial search engine: see Grub (search engine) a number of places in Switzerland, Austria and Germany, such as: Grub, canton of Appenzell Outer Rhodes, Switzerland Grub, Germany for the GNU project...
It has been suggested that this article or section be merged with foo. ...
This article does not cite any references or sources. ...
Grub or GRUB can mean: a slang term for food a beetle larva that resembles a worm a distributed commercial search engine: see Grub (search engine) a number of places in Switzerland, Austria and Germany, such as: Grub, canton of Appenzell Outer Rhodes, Switzerland Grub, Germany for the GNU project...
For BSD variants, on most platforms, the bootstrap program can be interrupted and given the boot -s command to boot into single-user mode. Single-user mode does not technically skip init; it still executes /sbin/init, but it will make init ask for the path to a program to exec() (the default being /bin/sh) instead of doing the regular multi-user boot sequence. If the tty the kernel was booted from was marked as "insecure" in the /etc/ttys file (on some systems, the current "securelevel" might also matter), init will first ask for the root password before allowing this (or fallback to multi-user mode if the user hits CTRL+D). If this program is exited, the kernel will restart init in multi-user mode. The same things will happen if the system is switched from multi-user to single-mode while running. If init cannot be started after the kernel booted, it will panic and the system will be unusable. Changing the path to init itself is done differently on different OSes (boot -a on NetBSD, the init_path loader variable on FreeBSD). TTY is a short form of several things: Short form of Teletype, in turn short form of Teletypewriter. ...
On many computer operating systems, superuser, or root, is the term used for the special user account that is controlled by the system administrator. ...
Other styles SystemStarter is a system program in Mac OS X that brings the computer system up from its initial starting state to a state where basic services are running and the user may log in. ...
launchd is a unified, open source service management framework for starting, stopping and managing daemons, programs and scripts. ...
Apple Inc. ...
Mac OS X (official IPA pronunciation: ) is a line of proprietary, graphical operating systems developed, marketed, and sold by Apple Inc. ...
This article or section contains information that has not been verified and thus might not be reliable. ...
Asynchrony is the state of not being synchronized. ...
In Unix computing, Upstart is an event-based replacement for the init daemon written by Scott James Remnant, an employee of Canonical Ltd. ...
Asynchrony is the state of not being synchronized. ...
Ubuntu (IPA pronunciation ) is a predominantly desktop-oriented Linux distribution, based on Debian GNU/Linux but with a stronger focus on usability, regular releases, and ease of installation. ...
Service Management Facility (SMF) is a new feature of the Solaris Operating System 10 that creates a supported, unified model for services and service management on each Solaris system and replaces init. ...
Solaris is a computer operating system developed by Sun Microsystems. ...
eINIT is a replacement for sysvinit, an init system used on Unix-based operating systems. ...
Asynchrony is the state of not being synchronized. ...
daemontools is a collection of tools for managing Unix services. ...
See also - pidof or killall5, another program from the System V set used in many distributions
pidof is a Linux utility that returns the process ID (PID) of a running process. ...
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