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NAME
init, telinit - process control initialization
SYNOPSIS
/sbin/init [0123456abcQqSs]
/etc/telinit [0123456abcQqSs]
DESCRIPTION
init is the default primordial user process. (Options given
to the kernel during boot may result in the invocation of an
alternative primordial user process, as described on
kernel(1M)). init initiates the core components of the ser-
vice management facility, svc.configd(1M) and
svc.startd(1M), and restarts these components if they fail.
For backwards compatibility, init also starts and restarts
general processes according to /etc/inittab, as desribed
below.
The run levels and system booting descriptions given below
are provided for compatibility purposes only, and otherwise
made obsolete by the service management facility, smf(5).
init Failure
If init exits for any reason other than system shutdown, it
will be restarted with process-ID 1.
Run Level Defined
At any given time, the system is in one of eight possible
run levels. A run level is a software configuration under
which only a selected group of processes exists. Processes
spawned by init for each of these run levels are defined in
/etc/inittab. init can be in one of eight run levels, 0-6
and S or s (S and s are identical). The run level changes
when a privileged user runs /sbin/init.
init and System Booting
When the system is booted, init is invoked and the following
occurs. First, it reads /etc/default/init to set environment
variables. This is typically where TZ (time zone) and
locale-related environments such as LANG or LC_CTYPE get
set. (See the FILES section at the end of this page.) init
then looks in /etc/inittab for the initdefault entry (see
inittab(4)). If the initdefault entry:
exists init usually uses the run level
specified in that entry as the ini-
tial run level to enter only if the
options/milestone property has not
been specified for svc.startd(1M).
does not exist The service management facility,
smf(5), examines its configuration
specified in svc.startd(1M), and
enters the milestone specified by
the options/milestone property.
The initdefault entry in /etc/inittab corresponds to the
following run levels:
S or s init goes to the single-user state.
In this state, the system console
device (/dev/console) is opened for
reading and writing and the command
/sbin/su, (see su(1M)), is invoked.
Use either init or telinit to change
the run level of the system. Note
that if the shell is terminated
(using an end-of-file), init only
re-initializes to the single-user
state if /etc/inittab does not
exist.
0-6 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 operat-
ing states.
If this is the first time since power up that init has
entered a run level other than single-user state, init first
scans /etc/inittab for boot and bootwait entries (see init-
tab(4)). These entries are performed before any other pro-
cessing of /etc/inittab takes place, providing that the run
level entered matches that of the entry. In this way any
special initialization of the operating system, such as
mounting file systems, can take place before users are
allowed onto the system. init then scans /etc/inittab and
executes all other entries that are to be processed for that
run level.
To spawn each process in /etc/inittab, init reads each entry
and for each entry that should be respawned, it forks a
child process. After it has spawned all of the processes
specified by /etc/inittab, init waits for one of its
descendant processes to die, a powerfail signal, or a signal
from another init or telinit process to change the system's
run level. When one of these conditions occurs, init re-
examines /etc/inittab.
inittab Additions
New entries can be added to /etc/inittab at any time; how-
ever, init still waits for one of the above three conditions
to occur before re-examining /etc/inittab. To get around
this, init Q or init q command wakes init to re-examine
/etc/inittab immediately.
When init comes up at boot time and whenever the system
changes from the single-user state to another run state,
init sets the ioctl(2) states of the console to those modes
saved in the file /etc/ioctl.syscon. init writes this file
whenever the single-user state is entered.
Run Level Changes
When a run level change request is made, init or a designate
sends the warning signal (SIGTERM) to all processes that are
undefined in the target run level. A minimum interval of
five seconds is observed before init or its designate forci-
bly terminates these processes by sending a kill signal
(SIGKILL). Additionally, init informs svc.startd(1M) that
the run level is changing. svc.startd(1M) then restricts the
system to the set of services which the milestone
corresponding to the run-level change depends on.
When init receives a signal telling it that a process it
spawned has died, it records the fact and the reason it died
in /var/adm/utmpx and /var/adm/wtmpx if it exists (see
who(1)). A history of the processes spawned is kept in
/var/adm/wtmpx.
If init receives a powerfail signal (SIGPWR) it scans
/etc/inittab for special entries of the type powerfail and
powerwait. These entries are invoked (if the run levels per-
mit) before any further processing takes place. In this way
init can perform various cleanup and recording functions
during the powerdown of the operating system.
Environment Variables in /etc/default/init
You can set default values for environment variables, for
such items as timezone and character formatting, in
/etc/default/init. See the FILES section, below, for a list
of these variables.
telinit
telinit, which is linked to /sbin/init, is used to direct
the actions of init. It takes a one-character argument and
signals init to take the appropriate action.
SECURITY
init uses pam(3PAM) for session management. The PAM confi-
guration policy, listed through /etc/pam.conf, specifies the
session management module to be used for init. Here is a
partial pam.conf file with entries for init using the UNIX
session management module.
init session required pam_unix_session.so.1
If there are no entries for the init service, then the
entries for the "other" service will be used.
OPTIONS
0 Go into firmware.
1 Put the system in system administrator mode.
All local file systems are mounted. Only a
small set of essential kernel processes are
left running. This mode is for administra-
tive tasks such as installing optional util-
ity packages. All files are accessible and
no users are logged in on the system.
This request corresponds to a request for
smf(5) to restrict the system milestone to
svc:/milestone/single-user:default.
2 Put the system in multi-user mode. All
multi-user environment terminal processes
and daemons are spawned. This state is com-
monly referred to as the multi-user state.
This request corresponds to a request for
smf(5) to restrict the system milestone to
svc:/milestone/multi-user:default.
3 Extend multi-user mode by making local
resources available over the network.
This request corresponds to a request for
smf(5) to restrict the system milestone to
svc:/milestone/multi-user-server:default.
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 Shut the machine down so that it is safe to
remove the power. Have the machine remove
power, if possible.
6 Stop the operating system and reboot to the
state defined by the initdefault entry in
/etc/inittab.
a,b,c Process only those /etc/inittab entries hav-
ing the a, b, or c run level set. These are
pseudo-states, which may be defined to run
certain commands, but which do not cause the
current run level to change.
Q,q Re-examine /etc/inittab.
S, s Enter single-user mode. This is the only run
level that doesn't require the existence of
a properly formatted /etc/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 in single-user
mode, the filesystems required for basic
system operation will be mounted. When the
system comes down to single-user mode, these
file systems will remain mounted (even if
provided by a remote file server), and any
other local filesystems will also be left
mounted. During the transition down to
single-user mode, all processes started by
init or init.d scripts that should only be
running in multi-user mode are killed. In
addition, any process that has a utmpx 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.
This request corresponds to a request for
smf(5) to restrict the system milestone to
svc:/milestone/single-user:default.
FILES
/dev/console System console device
/etc/default/init Contains environment variables and
their default values. For example,
for the timezone variable, TZ, you
might specify TZ=US/Pacific. The
variables are:
TZ Either specifies the
timezone information
(see ctime(3C)) or
the name of a
timezone information
file
/usr/share/lib/zoneinfo.
Refer to the
TIMEZONE(4) man page
before changing this
setting.
CMASK The mask (see
umask(1)) that init
uses and that every
process inherits
from the init pro-
cess. If not set,
init uses the mask
it inherits from the
kernel. Note that
init always attempts
to apply a umask of
022 before creating
a file, regardless
of the setting of
CMASK
LC_CTYPE Character character-
ization information
LC_MESSAGES Message translation
LC_MONETARY Monetary formatting
information
LC_NUMERIC Numeric formatting
information
LC_TIME Time formatting
information
LC_ALL If set, all other
LC_* environmental
variables take-on
this value.
LANG If LC_ALL is not
set, and any partic-
ular LC_* is also
not set, the value
of LANG is used for
that particular
environmental vari-
able.
/etc/initpipe A named pipe used for internal com-
munication
/etc/inittab Controls process dispatching by init
/etc/ioctl.syscon ioctl states of the console, as
saved by init when single-user state
is entered
/var/adm/utmpx User access and administration
information
/var/adm/wtmpx History of user access and adminis-
tration information
/var/run/init.state init state necessary to recover from
failure.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
SEE ALSO
login(1), sh(1), stty(1), who(1), kernel(1M), shutdown(1M),
su(1M), svc.configd(1M), svc.startd(1M), ttymon(1M),
ioctl(2), kill(2), ctime(3C), pam(3PAM), init.d(4), init-
tab(4), pam.conf(4), TIMEZONE(4), utmpx(4), attributes(5),
pam_unix_session(5), smf(5), termio(7I)
DIAGNOSTICS
If init finds that it is respawning an entry from
/etc/inittab more than ten times in two minutes, it assumes
that there is an error in the command string in the entry
and generates an error message on the system console. It
then refuses to respawn this entry until either five minutes
has elapsed or it receives a signal from a user-spawned init
or telinit command. This prevents init from eating up system
resources when someone makes a typographical error in the
inittab file, or a program is removed that is referenced in
/etc/inittab.
NOTES
init and telinit can be run only by a privileged user.
The S or s state must not be used indiscriminately in
/etc/inittab. When modifying this file, it is best to avoid
adding this state to any line other than initdefault.
If a default state is not specified in the initdefault entry
in /etc/inittab, state 6 is entered. Consequently, the sys-
tem will loop by going to firmware and rebooting continu-
ously.
If the utmpx file cannot be created when booting the system,
the system will boot to state "s" regardless of the state
specified in the initdefault entry in /etc/inittab. This can
occur if the /var file system is not accessible.
When a system transitions down to the S or s state, the
/etc/nologin file (see nologin(4)) is created. Upon subse-
quent transition to run level 2, this file is removed.
init uses /etc/initpipe, a named pipe, for internal communi-
cation.
The pam_unix(5) module is no longer supported. Similar func-
tionality is provided by pam_unix_session(5).