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.\" Donn Seeley at Berkeley Software Design, Inc.
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.\" @(#)init.8 6.7 (Berkeley) 6/2/93
.Nd process control initialization
is the last stage of the boot process.
It normally runs the automatic reboot sequence as described in
and if this succeeds, begins multi-user operation.
If the reboot scripts fail,
commences single user operation by giving
the super-user a shell on the console.
program may be passed parameters
prevent the system from going multi-user and to instead execute
a single 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).
start up command file in fastboot mode (skipping disk checks).
file is marked ``insecure'',
will require that the superuser password be
entered before the system will start a single-user shell.
The password check is skipped if the
The kernel runs with four different levels of security.
Any superuser process can raise the security level, but only
Security levels are defined as follows:
Permanently insecure mode \- always run system in level 0 mode.
Insecure mode \- immutable and append-only flags may be turned off.
All devices may be read or written subject to their permissions.
Secure mode \- immutable and append-only flags may not be changed;
disks for mounted filesystems,
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
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
If it is desired to run the system in level 0 mode while multiuser,
the administrator must build a kernel with the variable
in the kernel source file
.Pa /sys/kern/kern_sysctl.c
processes for the terminal ports found in the file
reads this file, and executes the command found in the second field.
opens and initializes the tty line
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),
program wakes up, deletes the user
file of current users and records the logout in the
Line status (on, off, secure, getty, or window information)
file without a reboot by sending the signal
On receipt of this signal,
When a line is turned off in
will send a SIGHUP signal to the controlling process
for the session associated with the line.
For any lines that were previously turned off in the
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
starts a process on the line).
If a line is commented out or deleted from
will not do anything at all to that line.
However, it will complain that the relationship between lines
so this practice is not recommended.
will terminate multi-user operations and resume single-user mode
If there are processes outstanding that are deadlocked (because of
hardware or software failure),
will not wait for them all to die (which might take forever), but
will time out after 30 seconds and print a warning message.
and allow the system to slowly die away, if it is sent a terminal stop
A later hangup will resume full
multi-user operations, or a terminate will start a single user shell.
is so critical that if it dies, the system will reboot itself
If, at bootstrap time, the
process cannot be located, the system will panic with the message
``panic: "init died (signal %d, exit %d)''.
.It "getty repeating too quickly on port %s, sleeping"
A process being started to service a line is exiting quickly
This is often caused by a ringing or noisy terminal line.
.Em "Init will sleep for 10 seconds" ,
.Em "then continue trying to start the process" .
.It "some processes would not die; ps axl advised."
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.
.Bl -tag -width /var/log/wtmp -compact
Record of Current users on the system.
Record of all logins and logouts.
The terminal initialization information file.
behave as though they have security level \-1.