Xref: utzoo comp.unix.questions:31162 comp.unix.misc:1430 comp.unix.sysv386:7951 Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!swrinde!mips!pacbell.com!att!cbfsb!cbnewsc!dcon From: dcon@cbnewsc.att.com (david.r.connet) Newsgroups: comp.unix.questions,comp.unix.misc,comp.unix.sysv386 Subject: Re: What is it? (was Re: Current Run-Level: How can you tell?) Message-ID: <1991May9.173444.8956@cbnewsc.att.com> Date: 9 May 91 17:34:44 GMT References: <1991Apr25.171617.13505@ssd.kodak.com> <230@harem.clydeunix.com> <602@fciva.FRANKCAP.COM> Organization: AT&T Bell Laboratories Lines: 69 In article <602@fciva.FRANKCAP.COM> dag@fciva.UUCP (Daniel A. Graifer) writes: > >On our Prime EXL's, which run pretty much Plain Vanilla AT&T SysV 3.1 with >some 3.2 extensions, we have: > > 0 - Shutdown System > 1 - Single User Mode > 2 - Normal Multi-User > 3 - Multiuser + remote file sharing > 4 - Undefined by system > 5 - Shutdown and entire ROM diagnostic monitor > 6 - Shutdown and reboot > >We've defined to state 4 to be system backup. A cron job in the wee dawn >hours does a telinit 4 to start the backup process. We also cleanup the >cron log at that time, since cron isn't running in state 4. > From the AT&T SVR4 init(1M) man page 0 shut the machine down so it is safe to remove the power. Have the machine remove power if it can. 1 put the system in system administrator mode. All file systems are mounted. Only a small set of essential kernel processes are left running. This mode is for administrative tasks such as installing optional utility packages. All files are accessible and no users are logged in on the system. 2 put the system in multi-user mode. All multi-user environment terminal processes and daemons are spawned. This state is commonly referred to as the multi-user state. 3 start the remote file sharing processes and daemons. Mount and advertise remote resources. Run level 3 extends multi-user mode and is known as the remote-file-sharing state. 4 is available to be defined as an alternative multi-user environment configuration. It is not necessary for system operation and is usually not used. 5 Stop the UNIX system and go to the firmware monitor. 6 Stop the UNIX system and reboot to the state defined by the initdefault entry in /sbin/inittab. S,s enter single-user mode. When this occurs, the terminal which executed this command becomes the system console. This is the only run level that doesn't require the existence of a properly formatted /sbin/inittab file. If this file does not exist, then by default the only legal run level that init can enter is the single-user mode. When the system comes up to S or s, file systems for users' files are not mounted and only essential kernel processes are running. When the system comes down to S or s, all mounted file systems remain mounted, and all processes started by init that should only be running in multi-user mode are killed. In addition, any process that has a utmp entry will be killed. This last condition insures that all port monitors started by the SAC are killed and all services started by these port monitors, including ttymon login services, are killed. Other processes not started directly by init will remain running. For example, cron remains running. If a 0 through 6 is entered, init enters the corresponding run level. Run levels 0, 5, and 6 are reserved states for shutting the system down. Run levels 2, 3, and 4 are available as multi-user operating states. Dave Connet dcon@iwtng.att.com