Manual Pages for UNIX Darwin command on man init

INIT(8) BSD System Manager's Manual INIT(8)

NAME

iinniitt - process control initialization

SYNOPSIS

iinniitt

DESCRIPTION

The iinniitt program is the last stage of the boot process. It normally runs

the automatic reboot sequence as described in reboot(8), and if this suc-

ceeds, begins multi-user operation. If the reboot scripts fail, iinniitt

commences single user operation by giving the super-user a shell on the

console. The iinniitt program may be passed parameters from the boot program

to prevent the system from going multi-user and to instead execute a sin-

gle user shell without starting the normal daemons. The system is then

quiescent for maintenance work and may later be made to go to multi-user

by exiting the single-user shell (with ^D). This causes iinniitt to run the

/etc/rc start up command file in fastboot mode (skipping disk checks). If the ccoonnssoollee entry in the ttys(5) file is marked ``insecure'', then

iinniitt will require that the superuser password be entered before the sys-

tem will start a single-user shell. The password check is skipped if the

ccoonnssoollee is marked as ``secure''. The kernel runs with four different levels of security. Any superuser

process can raise the security level, but only iinniitt can lower it. Secu-

rity levels are defined as follows:

-11 Permanently insecure mode - always run system in level 0 mode.

00 Insecure mode - immutable and append-only flags may be turned off.

All devices may be read or written subject to their permissions.

11 Secure mode - immutable and append-only flags may not be changed;

disks for mounted filesystems, /dev/mem, and /dev/kmem are read-

only. The settimeofday(2) system call can only advance the time.

22 Highly secure mode - same as secure mode, plus disks are always

read-only whether mounted or not. This level precludes tampering

with filesystems by unmounting them, but also inhibits running

newfs(8) while the system is multi-user.

Normally, the system runs in level 0 mode while single user and in level 1 mode while multiuser. If the level 2 mode is desired while running multiuser, it can be set in the startup script /etc/rc using sysctl(8). If it is desired to run the system in level 0 mode while multiuser, the administrator must build a kernel with the variable sseeccuurreelleevveell defined

in the file /sys/compile/MACHINE/param.c and initialize it to -1.

In multi-user operation, iinniitt maintains processes for the terminal ports

found in the file ttys(5). IInniitt reads this file, and executes the com-

mand found in the second field. This command is usually getty(8); getty

opens and initializes the tty line and executes the login program. The

login program, when a valid user logs in, executes a shell for that user. When this shell dies, either because the user logged out or an abnormal termination occurred (a signal), the iinniitt program wakes up, deletes the user from the utmp(5) file of current users and records the logout in the wtmp file. The cycle is then restarted by iinniitt executing a new getty for the line. Line status (on, off, secure, getty, or window information) may be changed in the ttys file without a reboot by sending the signal SIGHUP to

iinniitt with the command ``kill -s HUP 1''. On receipt of this signal, iinniitt

re-reads the ttys file. When a line is turned off in ttys, iinniitt will

send a SIGHUP signal to the controlling process for the session associ-

ated with the line. For any lines that were previously turned off in the ttys file and are now on, iinniitt executes a new getty to enable a new login. If the getty or window field for a line is changed, the change takes effect at the end of the current login session (e.g., the next time iinniitt starts a process on the line). If a line is commented out or

deleted from ttys, iinniitt will not do anything at all to that line. How-

ever, it will complain that the relationship between lines in the ttys file and records in the utmp file is out of sync, so this practice is not recommended.

IInniitt will terminate multi-user operations and resume single-user mode if

sent a terminate (TERM) signal, for example, ``kill -s TERM 1''. If

there are processes outstanding that are deadlocked (because of hardware

or software failure), init will not wait for them all to die (which might

take forever), but will time out after 30 seconds and print a warning message. IInniitt will cease creating new getty's and allow the system to slowly die

away, if it is sent a terminal stop (TSTP) signal, i.e. ``kill -s TSTP

1''. A later hangup will resume full multi-user operations, or a termi-

nate will start a single user shell. This hook is used by reboot(8) and halt(8). The role of iinniitt is so critical that if it dies, the system will reboot

itself automatically. If, at bootstrap time, the init process cannot be

located, the system will panic with the message ``panic: "init died (sig-

nal %d, exit %d)''.

DIAGNOSTICS

ggeettttyy rreeppeeaattiinngg ttoooo qquuiicckkllyy oonn ppoorrtt %%ss,, sslleeeeppiinngg A process being started

to service a line is exiting quickly each time it is started. This is often caused by a ringing or noisy terminal line. Init will sleep for 10 seconds, then continue trying to start the process. ssoommee pprroocceesssseess wwoouulldd nnoott ddiiee;; ppss aaxxll aaddvviisseedd.. A process is hung and could not be killed when the system was shutting down. This condition is usually caused by a process that is stuck in a device driver because of a persistent device error condition. FILES /dev/console System console device. /dev/tty* Terminal ports found in ttys. /var/run/utmp Record of Current users on the system. /var/log/wtmp Record of all logins and logouts.

/etc/ttys The terminal initialization information file.

/etc/rc System startup commands.

BUGS

Systems without sysctl behave as though they have security level -1.

4th Berkeley Distribution May 26, 1995 4th Berkeley Distribution