151:
129:
32:
362:
393:. At least one runlevel is the normal operating state of the system; typically, other runlevels represent single-user mode (used for repairing a faulty system), system shutdown, and various other states. Switching from one runlevel to another causes a per-runlevel set of scripts to be run, which typically mount filesystems, start or stop
632:
On Unix systems, changing the runlevel is achieved by starting only the missing services (as each level defines only those that are started / stopped). For example, changing a system from runlevel 3 to 4 might only start the local X server. Going back to runlevel 3, it would be stopped again.
419:
in System V describe certain states of a machine, characterized by the processes and daemons running in each of them. In general, there are seven runlevels, out of which three runlevels are considered "standard", as they are essential to the operation of a system:
302:
file determines what programs are run by init. The advantage of this system is that it is simple and easy to edit manually. However, new software added to the system may require changes to existing files that risk producing an unbootable system.
348:
directory. Unlike System V's script ordering, which is derived from the filename of each script, this system uses explicit dependency tags placed within each script. The order in which scripts are executed is determined by the
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641:
Traditionally, one of the major drawbacks of init is that it starts tasks serially, waiting for each to finish loading before moving on to the next. When startup processes end up
1422:
1656:
1075:
803:, a software suite, full replacement for init in Linux that includes an init daemon, with concurrent starting of services, service manager, and other features.
645:(I/O) blocked, this can result in long delays during boot. Speeding up I/O, e.g. by using SSDs, may shorten the delays but it does not address the root cause.
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251:
Since then, several additional init implementations have been created, attempting to address design limitations in the traditional versions. These include
53:
46:
1137:
794:
738:, a process spawner that utilizes system-provided init, while providing process isolation, parallelized startup, and service dependency; used by
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881:
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On Linux distributions defaulting to runlevel 5 in the table on the right, runlevel 5 invokes a multiuser graphical environment running the
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Various efforts have been made to replace the traditional init daemons to address this and other design problems, including:
451:
Aside from these standard ones, Unix and Unix-like systems treat runlevels somewhat differently. The common denominator, the
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employed a traditional init that was somewhat compatible with System V, while some distributions such as
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will occur if the kernel is unable to start it, or it should die for any reason. Init is typically assigned
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operating systems typically reserve runlevel 5 to shut down and automatically power off the machine.
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202:
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service and daemon manager which provides asynchronous, dependency-based initialisation; written in
759:, a cross-platform full replacement for init with parallel starting of services, used by default in
873:
777:
starting with
Solaris 10, but launched as the only service by the original System V-style init
380:
introduced a new style of system startup configuration, which survived (with modifications) into
64:
42:
1018:
995:
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20:
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823:
and used by them until 2014. It was also used in Fedora 9, Red Hat
Enterprise Linux 6 and
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425:
193:
process that continues running until the system is shut down. It is the direct or indirect
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At any moment, a running System V is in one of the predetermined number of states, called
8:
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819:, a full replacement of init designed to start processes asynchronously. Initiated by
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732:(it launches SystemStarter to run old-style 'rc.local' and SystemStarter processes)
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314:
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1162:
700:, a single-threaded Linux init system focused on simplicity and service management
89:
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652:
572:
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398:
377:
318:
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228:, the design of init has diverged from the functionality provided by the init in
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utility that selects which SysV-style init scripts will be run in each runlevel
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On most systems, all users can check the current runlevel with either the
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706:, a full replacement of init designed to start processes asynchronously
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604:
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and meant to be interactively hackable during normal system operation
769:(SMF), a complete replacement/redesign of init from the ground up in
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455:
file, defines what each configured runlevel does in a given system.
31:
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file that is run in a sub-shell near the end of the boot sequence.
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init was, prior to 4.3BSD, the same as
Research UNIX's init; in
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1184:"GitHub - davmac314/dinit: Service monitoring / "init" system"
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1630:
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717:
504:
484:
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19:
This article is about the Unix process. For other uses, see
1520:
725:
613:
user typically changes the current runlevel by running the
166:
784:
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1239:
353:
utility based on the requirements stated in these tags.
344:
5.0 and successors. This system executes scripts in the
874:"Lennart Poettering on systemd's Tumultuous Ascendancy"
1469:
Solaris
Service Management Facility - Quickstart Guide
809:, a process spawner started by the BSD-style init in
197:
of all other processes and automatically adopts all
1418:
746:and its derivatives, and available as an option in
329:, BSD variants have long supported a site-specific
1657:Unix process- and task-management-related software
1479:A history of modern init systems (1992–2015)
244:use BSD-style startup scripts, and others such as
797:, a software suite that includes an init system.
1648:
1039:
274:
1161:. Unixhelp.ed.ac.uk. 1997-05-27. Archived from
384:and is therefore called the "SysV-style init".
509:3 (console/server/multiuser) or 4 (graphical)
376:When compared to its predecessors, AT&T's
1506:
321:on graphical terminals under the control of
236:derivatives. Up until the early 2010s, most
1388:Red Hat Enterprise Linux 6: Technical Notes
1130:Oracle Solaris Administration: Common Tasks
835:As of February 2019, systemd has been
336:A fully modular system was introduced with
1513:
1499:
1409:
694:Dinit, a service manager and init system.
116:Learn how and when to remove this message
1042:"Unix and Linux startup scripts, Part 2"
636:
625:file sets the default runlevel with the
360:
149:
127:
1649:
52:Please improve this article by adding
1494:
1463:A paper summarizing Unix init schemes
1048:from the original on 18 December 2009
1159:"UNIX man pages : runlevel (8)"
1040:Andrew Smallshaw (7 December 2009).
458:
325:. To remove the requirement to edit
248:have their own customized versions.
25:
1290:"s6: why another supervision suite"
849:Operating system service management
839:by most major Linux distributions.
189:of the operating system. Init is a
13:
294:on terminals under the control of
14:
1668:
1475: (archived December 31, 2005)
1451:
1425:from the original on 9 April 2022
1361:. Linux Weekly News. 2010-09-14.
1267:. Free Software Foundation, Inc.
813:prior to Mac OS X v10.4
313:, it added support for running a
30:
1436:
1398:from the original on 2018-08-29
1376:
1365:from the original on 2010-09-19
1351:
1341:from the original on 2022-03-27
1325:
1307:
1296:from the original on 2021-09-13
1282:
1271:from the original on 2016-02-12
1257:
1246:from the original on 2020-08-29
1232:
1221:from the original on 2014-08-02
1207:
1196:from the original on 2021-12-12
1176:
1151:
1140:from the original on 2016-04-10
1118:
1107:from the original on 2020-12-03
1089:
1078:from the original on 2021-07-27
884:from the original on 2018-11-08
154:Version 7 Unix: contents of an
1359:"Fedora defers systemd to F15"
1060:
1033:
1010:
987:
964:
941:
918:
895:
866:
298:. There are no runlevels; the
1:
860:
856:— an equivalent in Windows NT
401:, shutdown the machine, etc.
356:
282:init runs the initialization
275:Research Unix-style/BSD-style
54:secondary or tertiary sources
1265:"The Shepherd - GNU Project"
1215:"Epoch Init System Homepage"
712:, a replacement for init in
688:before it was replaced with
404:
7:
1605:Service Management Facility
1334:Fedora 14 Accepted Features
842:
767:Service Management Facility
257:Service Management Facility
10:
1673:
1103:. Gentoo.org. 2014-12-13.
1101:Gentoo Linux Documentation
666:embedded operating systems
408:
18:
1615:
1565:Operating-system-specific
1564:
1533:
854:Session Manager Subsystem
201:. Init is started by the
1534:Portable implementations
730:Mac OS X v10.4
220:In Unix systems such as
443:
429:
424:
1240:"Void Linux main page"
373:
162:
147:
41:relies excessively on
1458:FreeBSD init man page
637:Other implementations
409:Further information:
364:
153:
131:
21:INIT (disambiguation)
16:UNIX system component
397:, start or stop the
1617:Process supervision
238:Linux distributions
1522:Service management
1484:2015-10-11 at the
811:Mac OS X
551:Releases 3.x, 4.x
515:Linux From Scratch
374:
340:1.5 and ported to
215:process identifier
199:orphaned processes
163:
148:
1644:
1643:
1004:System Manager's
958:System Manager's
575:, usually with a
569:
568:
469:Default runlevel
466:Operating system
459:Default runlevels
171:operating systems
139:listing, showing
126:
125:
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1444:Systemd#Adoption
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1317:. Archived from
1315:"s6 init system"
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678:Tiny Core Linux
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587:. However, the
577:display manager
573:X Window System
525:Slackware Linux
461:
452:
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433:(also known as
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399:X Window System
378:UNIX System III
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185:started during
181:) is the first
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47:primary sources
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1452:External links
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1350:
1337:, 2010-07-13,
1324:
1321:on 2021-09-13.
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1206:
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1059:
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933:Version 7 Unix
917:
910:Version 7 Unix
894:
880:. 2018-11-08.
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179:initialization
133:Version 7 Unix
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1595:SystemStarter
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1165:on 2014-07-14
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1097:"Initscripts"
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1027:File Formats
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981:File Formats
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977: –
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935:Programmer's
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912:Programmer's
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878:The New Stack
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627::initdefault:
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331:/etc/rc.local
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106:December 2020
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67: –
66:
62:
61:Find sources:
55:
49:
48:
44:
39:This article
37:
33:
28:
27:
22:
1540:
1438:
1427:, retrieved
1417:
1411:
1400:. Retrieved
1387:
1384:"Deployment"
1378:
1367:. Retrieved
1353:
1343:, retrieved
1333:
1327:
1319:the original
1309:
1298:. Retrieved
1284:
1273:. Retrieved
1259:
1248:. Retrieved
1234:
1223:. Retrieved
1209:
1198:. Retrieved
1187:
1178:
1167:. Retrieved
1163:the original
1153:
1142:. Retrieved
1129:
1126:"Run Levels"
1120:
1109:. Retrieved
1100:
1091:
1080:. Retrieved
1071:
1062:
1050:. Retrieved
1035:
1012:
989:
966:
943:
920:
897:
886:. Retrieved
877:
868:
834:
789:Guile Scheme
740:Alpine Linux
676:5(Rolling),
670:Alpine Linux
664:, suited to
662:busybox-init
647:
643:Input/output
640:
631:
623:/etc/inittab
597:
570:
495:Gentoo Linux
453:/etc/inittab
450:
438:
434:
414:
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386:
375:
366:sysv-rc-conf
350:
335:
305:
284:shell script
278:
250:
219:
211:kernel panic
178:
174:
164:
159:Bourne shell
112:
103:
93:
86:
79:
72:
60:
40:
1626:daemontools
752:Artix Linux
682:VMware ESXi
653:BootScripts
286:located at
209:process; a
205:during the
177:(short for
1429:25 January
1402:2013-12-31
1369:2010-09-17
1345:2010-07-13
1300:2021-09-13
1275:2016-01-16
1250:2020-08-31
1225:2014-07-31
1200:2021-12-12
1169:2014-07-12
1144:2017-11-14
1111:2020-12-08
1082:2015-09-12
888:2024-01-30
861:References
761:Void Linux
668:, used by
357:SysV-style
222:System III
76:newspapers
43:references
1526:Unix-like
1068:"init(8)"
657:GoboLinux
417:runlevels
405:Runlevels
390:runlevels
346:/etc/rc.d
323:/etc/ttys
296:/etc/ttys
242:Slackware
1651:Category
1601:Solaris
1482:Archived
1423:archived
1396:Archived
1363:Archived
1339:archived
1294:Archived
1269:Archived
1244:Archived
1219:Archived
1194:Archived
1138:Archived
1105:Archived
1076:Archived
1046:Archived
882:Archived
843:See also
829:ChromeOS
781:Shepherd
600:runlevel
560:UnixWare
426:Turn off
411:Runlevel
317:such as
232:and its
226:System V
195:ancestor
1590:launchd
1580:Upstart
1575:systemd
1528:systems
1471:at the
1392:Red Hat
1019:ttys(5)
996:init(8)
973:ttys(5)
950:init(8)
927:ttys(5)
904:init(8)
837:adopted
817:Upstart
801:systemd
775:Solaris
771:illumos
710:launchd
686:OpenWrt
629:entry.
615:telinit
593:illumos
589:Solaris
539:illumos
535:Solaris
395:daemons
351:rcorder
342:FreeBSD
327:/etc/rc
300:/etc/rc
288:/etc/rc
261:systemd
253:launchd
207:booting
187:booting
183:process
156:/etc/rc
90:scholar
1586:macOS
1571:Linux
1551:OpenRC
1546:Initng
1465:(2007)
1189:GitHub
1134:Oracle
1052:6 June
1029:Manual
1025:4.3BSD
1006:Manual
1002:4.3BSD
983:Manual
979:4.2BSD
960:Manual
956:4.2BSD
937:Manual
914:Manual
825:Google
821:Ubuntu
783:, the
748:Devuan
744:Gentoo
736:OpenRC
714:Darwin
704:Initng
680:, and
674:SliTaz
445:Reboot
338:NetBSD
311:4.3BSD
269:OpenRC
255:, the
246:Gentoo
203:kernel
191:daemon
161:script
92:
85:
78:
71:
65:"Init"
63:
1636:runit
1631:monit
1619:tools
1556:runit
757:runit
718:macOS
698:Epoch
690:procd
579:like
505:HP-UX
485:antiX
292:getty
265:Runit
97:JSTOR
83:books
1541:init
1442:See
1431:2014
1054:2011
765:Sun
750:and
726:tvOS
619:init
611:root
591:and
562:7.x
415:The
368:, a
267:and
224:and
175:init
167:Unix
143:and
141:init
137:/etc
69:news
1524:in
827:'s
785:GNU
722:iOS
655:in
617:or
605:who
602:or
585:KDM
583:or
581:GDM
475:AIX
437:or
370:TUI
307:BSD
234:BSD
217:1.
165:In
45:to
1653::
1421:,
1394:.
1390:.
1386:.
1292:.
1242:.
1217:.
1192:.
1186:.
1136:.
1132:.
1128:.
1099:.
1074:.
1070:.
1044:.
876:.
795:s6
742:,
672:,
607:-r
565:3
554:2
543:3
537:/
529:3
519:3
499:3
489:5
479:2
271:.
263:,
259:,
173:,
145:rc
135::
56:.
1514:e
1507:t
1500:v
1405:.
1372:.
1303:.
1278:.
1253:.
1228:.
1203:.
1172:.
1147:.
1114:.
1085:.
1056:.
891:.
831:.
773:/
724:/
720:/
716:/
441:)
439:s
435:S
319:X
119:)
113:(
108:)
104:(
94:·
87:·
80:·
73:·
50:.
23:.
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