System Administration Commands init(1M)
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 LCTYPE 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 initial run level to enter only if the
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System Administration Commands init(1M)
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 pro-
perty.
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 read-
ing 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 ter-
minated (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
operating 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
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specified by /etc/inittab, init waits for one of its descen-
dant 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
(SIGKIL). 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.
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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 pamunixsession.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
administrative tasks such as installing optional utility
packages. All files are accessible and no users are
logged in on the system.
This request corresponds to a request for smf(5) to res-
trict 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 commonly referred to as the multi-user
state.
This request corresponds to a request for smf(5) to res-
trict the system milestone to svc:/milestone/multi-
user:default.
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3
Extend multi-user mode by making local resources avail-
able over the network.
This request corresponds to a request for smf(5) to res-
trict 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 sys-
tem 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 having 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
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System Administration Commands init(1M)
by a remote file server), and any other local filesys-
tems 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 res-
trict 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 process. 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 set-
ting of CMASK
LCTYPE
Character characterization information
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LCMESAGES
Message translation
LCMONETARY
Monetary formatting information
LCNUMERIC
Numeric formatting information
LCTIME
Time formatting information
LCAL
If set, all other LC* environmental variables
take-on this value.
LANG
If LCAL is not set, and any particular LC* is
also not set, the value of LANG is used for that
particular environmental variable.
/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
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History of user access and administration information.
/var/run/init.state
init state necessary to recover from failure.
/var/run/initpipe
A named pipe used for internal communication.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE 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),
pamunixsession(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.
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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 /var/run/initpipe, a named pipe, for internal com-
munication.
The pamunix(5) module is no longer supported. Similar func-
tionality is provided by pamunixsession(5).
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