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Init
In Unix-based computer operating systems, init (short for ''initialization'') is the first process started during booting of the computer system. Init is a daemon process that continues running until the system is shut down. It is the direct or indirect ancestor of all other processes and automatically adopts all orphaned processes. Init is started by the kernel during the booting process; a kernel panic will occur if the kernel is unable to start it. Init is typically assigned process identifier 1. In Unix systems such as System III and System V, the design of init has diverged from the functionality provided by the init in Research Unix and its BSD derivatives. Up until recently, most Linux distributions employed a traditional init that was somewhat compatible with System V, while some distributions such as Slackware use BSD-style startup scripts, and others such as Gentoo have their own customized versions. Since then, several additional init implementations ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Systemd
systemd is a software suite that provides an array of system components for Linux operating systems. Its main aim is to unify service configuration and behavior across Linux distributions; Its primary component is a "system and service manager"—an init system used to bootstrap user space and manage user processes. It also provides replacements for various daemons and utilities, including device management, login management, network connection management, and event logging. The name ''systemd'' adheres to the Unix convention of naming daemons by appending the letter ''d''. It also plays on the term "System D", which refers to a person's ability to adapt quickly and improvise to solve problems. Since 2015, the majority of Linux distributions have adopted systemd, having replaced other init systems such as SysV init. It has been praised by developers and users of distributions that adopted it for providing a stable, fast out-of-the-box solution for issues that had existed i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Booting
In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some process must load software into memory before it can be executed. This may be done by hardware or firmware in the CPU, or by a separate processor in the computer system. Restarting a computer also is called rebooting, which can be "hard", e.g. after electrical power to the CPU is switched from off to on, or "soft", where the power is not cut. On some systems, a soft boot may optionally clear RAM to zero. Both hard and soft booting can be initiated by hardware such as a button press or by a software command. Booting is complete when the operative runtime system, typically the operating system and some applications,Including daemons. is attained. The process of returning a computer from a state of sleep (suspension) does not involve bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Launchd
launchd is an init and operating system service management daemon created by Apple Inc. as part of macOS to replace its BSD-style init and SystemStarter. There have been efforts to port launchd to FreeBSD and derived systems. Components There are two main programs in the launchd system: launchd and launchctl. ''launchd'' manages the daemons at both a system and user level. Similar to xinetd, launchd can start daemons on demand. Similar to watchdogd, launchd can monitor daemons to make sure that they keep running. launchd also has replaced init as PID 1 on macOS and as a result it is responsible for starting the system at boot time. Configuration files define the parameters of services run by launchd. Stored in the LaunchAgents and LaunchDaemons subdirectories of the Library folders, the property list-based files have approximately thirty different keys that can be set. launchd itself has no knowledge of these configuration files or any ability to read them - that is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OpenRC
OpenRC is a dependency-based init system for Unix-like computer operating systems. It was created by Roy Marples, a NetBSD developer who was also active in the Gentoo project. It became more broadly adopted as an init system outside of Gentoo following the decision by some Linux distributions not to adopt systemd. Adoption OpenRC is the default init system and/or process supervisor for: * Alpine Linux * Funtoo * Gentoo Linux * Hyperbola GNU/Linux-libre * Maemo Leste * Nitrux OpenRC is an available init system and/or process supervisor for: * Artix Linux * Devuan * Parabola GNU/Linux-libre * Arch Linux Design OpenRC is made up of several modular components, the main ones being an init (optional), the core dependency management system and a daemon supervisor (optional). It is written in C and POSIX-compliant shell, making it usable on BSD and Linux systems. The core part of OpenRC handles dependency management and init script parsing. OpenRC works by scanning the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
FreeBSD
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular open-source BSD operating system, accounting for more than three-quarters of all installed and permissively licensed BSD systems. FreeBSD has similarities with Linux, with two major differences in scope and licensing: FreeBSD maintains a complete system, i.e. the project delivers a kernel, device drivers, userland utilities, and documentation, as opposed to Linux only delivering a kernel and drivers, and relying on third-parties for system software; FreeBSD source code is generally released under a permissive BSD license, as opposed to the copyleft GPL used by Linux. The FreeBSD project includes a security team overseeing all software shipped in the base distribution. A wide range of additional third-party applications may be installe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Runit
runit is an init and service management scheme for Unix-like operating systems that initializes, supervises, and ends processes throughout the operating system. Runit is a reimplementation of the daemontools process supervision toolkit that runs on many Linux-based operating systems, as well as BSD, and Solaris operating systems. Runit features parallelization of the start up of system services, which can speed up the boot time of the operating system. When running as an init daemon, Runit is the direct or indirect ancestor of all other processes. It is the first process started during booting, and continues running until the system is shut down. It is often used with other init systems as a separate service manager. In the service manager role, it can be used by unprivileged users to orchestrate personal services, as well as by root to manage services not otherwise managed by the init system currently in use. Design Runit focuses on being a small, modular, and portable codeb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UNIX System V
Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, and 4. System V Release 4 (SVR4) was commercially the most successful version, being the result of an effort, marketed as ''Unix System Unification'', which solicited the collaboration of the major Unix vendors. It was the source of several common commercial Unix features. System V is sometimes abbreviated to SysV. , the AT&T-derived Unix market is divided between four System V variants: IBM's AIX, Hewlett Packard Enterprise's HP-UX and Oracle's Solaris, plus the free-software illumos forked from OpenSolaris. Overview Introduction System V was the successor to 1982's UNIX System III. While AT&T developed and sold hardware that ran System V, most customers ran a version from a reseller, based on AT&T's reference implementation. A s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Runlevel
A runlevel is a mode of operation in the computer operating systems that implements Unix System V-style initialization. Conventionally, seven runlevels exist, numbered from zero to six. ''S'' is sometimes used as a synonym for one of the levels. Only one runlevel is executed on startup; run levels are not executed one after another (i.e. only runlevel 2, 3, or 4 is executed, not more of them sequentially or in any other order). A runlevel defines the state of the machine after boot. Different runlevels are typically assigned (not necessarily in any particular order) to the single-user mode, multi-user mode without network services started, multi-user mode with network services started, system shutdown, and system reboot system states. The exact setup of these configurations varies between operating systems and Linux distributions. For example, runlevel 4 might be a multi-user GUI no-server configuration on one distribution, and nothing on another. Runlevels commonly follow the gen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley (Berkeley Software Distribution, BSD), Microsoft (Xenix), Sun Microsystems (SunOS/Solaris (operating system), Solaris), Hewlett-Packard, HP/Hewlett Packard Enterprise, HPE (HP-UX), and IBM (IBM AIX, AIX). In the early 1990s, AT&T sold its rights in Unix to Novell, which then sold the UNIX trademark to The Open Group, an industry consortium founded in 1996. The Open Group allows the use of the mark for certified operating systems that comply with the Single UNIX Specification (SUS). Unix systems are chara ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gentoo Linux
Gentoo Linux (pronounced ) is a Linux distribution built using the Portage package management system. Unlike a binary software distribution, the source code is compiled locally according to the user's preferences and is often optimized for the specific type of computer. Precompiled binaries are available for some larger packages or those with no available source code. Gentoo Linux was named after the gentoo penguin, the fastest swimming species of penguin. The name was chosen to reflect the potential speed improvements of machine-specific optimization, which is a major feature of Gentoo. Gentoo package management is designed to be modular, portable, easy to maintain, and flexible. Gentoo describes itself as a meta-distribution because of its adaptability, in that the majority of users have configurations and sets of installed programs which are unique to the system and the applications they use. History Gentoo Linux was initially created by Daniel Robbins as the ''Enoch Linu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Getty (Unix)
getty, short for "get tty", is a Unix program running on a host computer that manages physical or virtual terminals (TTYs). When it detects a connection, it prompts for a username and runs the 'login' program to authenticate the user. Originally, on traditional Unix systems, getty handled connections to serial terminals (often Teletype machines) connected to a host computer. The ''tty'' part of the name stands for ''Teletype'', but has come to mean any type of text terminal. One ''getty'' process serves one terminal. In some systems, for example, Solaris, ''getty'' was replaced by ttymon. Personal computers running Unix-like operating systems, even if they do not provide any remote login services, may still use ''getty'' as a means of logging in on a local virtual console. Instead of the ''login'' program, ''getty'' may also be set up by the system administrator to run any other program, for example pppd ( point-to-point protocol daemon) to provide a dial-up Internet connectio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shell Script
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text. A script which sets up the environment, runs the program, and does any necessary cleanup or logging, is called a wrapper. The term is also used more generally to mean the automated mode of running an operating system shell; each operating system uses a particular name for these functions including batch files (MSDos-Win95 stream, OS/2), command procedures (VMS), and shell scripts (Windows NT stream and third-party derivatives like 4NT—article is at cmd.exe), and mainframe operating systems are associated with a number of terms. Shells commonly present in Unix and Unix-like systems include the Korn shell, the Bourne shell, and GNU Bash. While a Unix operating system may have a different d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
