is the last stage of the boot process.
It normally executes the sequence of events described in
and if this succeeds, begins multi-user operation.
If the boot scripts fail,
commences single-user operation by giving
the superuser a shell on the console.
program 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 following parameters may be passed from the boot program:
Activate fastboot mode.
Boot directly into single user mode.
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
startup command file in fastboot mode (skipping disk checks).
entry in the
file does not contain the
will require that the superuser password be
entered before the system will start a single-user shell.
The password check is skipped if the
is marked as
is normally set to 0 while in single-user mode, and raised to 1 when
the system begins multi-user operations.
This action will not take
place if the securelevel is \-1, and can be modified via the
In multi-user operation,
processes for the terminal ports found in the file
reads this file, and executes the command found in the second field.
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),
program wakes up, deletes the user
file of current users and records the logout in the
The cycle is
then restarted by
executing a new
for the line.
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 \-s HUP 1".
On receipt of this signal,
When a line is turned off in
will send a
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 a new
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
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
file and records in the
file is out of sync,
so this practice is not recommended.
will terminate multi-user operations and resume single-user mode
if sent a terminate
signal, for example,
"kill \-s 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.
will cease creating new
and allow the system to slowly die away, if it is sent a terminal stop
"kill \-s 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
will terminate multi-user operations, kill all
and halt the machine if user-defined signal 1
or user-defined signal 2
.Pd Dv USR2
can specify that a powerdown is requested.
specifically requests a powerdown.
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).
spawns a process it sets the process priority, umask, and resource
limits based on
When starting the
files, the login class
When starting a window system or
the login class
No resource changes are made when entering single user mode.
system console device
terminal ports found in
system startup commands
commands that run before the security level changes
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".
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.