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.
utility may be passed parameters
from the boot program to
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).
to run the
start up command file in fastboot mode (skipping disk checks).
entry in the
file is marked
will require that the super-user password be
entered before the system will start a single-user shell.
The password check is skipped if the
is marked as
If the system security level (see
is initially nonzero, then
leaves it unchanged.
raises the level to 1 before going multi-user for the first time.
Since the level cannot be reduced, it will be at least 1 for
subsequent operation, even on return to single-user.
If a level higher than 1 is desired while running multi-user,
it can be set before going multi-user, e.g., by the startup script
to set the
variable to the required security level.
is run in a jail, the security level of the
will not be affected.
Part of the information set up in the kernel to support a jail
is a per-jail security level.
This allows running a higher security level inside of a jail
than that of the host system.
for more information about jails.
In multi-user operation,
processes for the terminal ports found in the file
utility reads this file and executes the command found in the second field,
unless the first field refers to a device in
which is not configured.
The first field is supplied as the final argument to the command.
This command is usually
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),
the cycle is restarted by
executing a new
for the line.
utility can also be used to keep arbitrary daemons running,
automatically restarting them if they die.
In this case, the first field in the
file must not reference the path to a configured device node
and will be passed to the daemon
as the final argument on its command line.
This is similar to the facility offered in the
Line status (on, off, secure, getty, or window information)
may be changed in the
file without a reboot by sending the signal
with the command
"kill -HUP 1".
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
file and are now on,
executes the command specified in the second field.
If the command 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.
utility will terminate multi-user operations and resume single-user mode
if sent a terminate
signal, for example,
"kill -TERM 1".
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.
utility will cease creating new processes
and allow the system to slowly die away, if it is sent a terminal stop
"kill -TSTP 1".
A later hangup will resume full
multi-user operations, or a terminate will start a single-user shell.
This hook is used by
utility will terminate all possible processes (again, it will not wait
for deadlocked processes) and reboot the machine if sent the interrupt
"kill -INT 1".
This is useful for shutting the machine down cleanly from inside the kernel
or from X when the machine appears to be hung.
utility will do the same, except it will halt the machine if sent
the user defined signal 1
or will halt and turn the power off (if hardware permits) if sent
the user defined signal 2
When shutting down the machine,
will try to run the
This script can be used to cleanly terminate specific programs such
(the InterNetNews server).
If this script does not terminate within 120 seconds,
will terminate it.
The timeout can be configured via the
The role of
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)".
If run as a user process as shown in the second synopsis line,
behavior, i.e., super-user can specify the desired
on a command line, and
will signal the original
| Run-level Signal Action
0 SIGUSR1 Halt
0 SIGUSR2 Halt and turn the power off
1 SIGTERM Go to single-user mode
6 SIGINT Reboot the machine
c SIGTSTP Block further logins
q SIGHUP Rescan the