init(1M) System Administration Commands init(1M)NAME
init, telinit - process control initialization
SYNOPSIS
/sbin/init [0123456abcQqSs]
/etc/telinit [0123456abcQqSs]
DESCRIPTIONinit is the default primordial user process. (Options given to the ker‐
nel during boot may result in the invocation of an alternative primor‐
dial user process, as described on kernel(1M)). init initiates the core
components of the service management facility, svc.configd(1M) and
svc.startd(1M), and restarts these components if they fail. For back‐
wards 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 con‐
sole 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-initial‐
izes 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 inittab(4)). These entries are performed
before any other processing of /etc/inittab takes place, providing that
the run level entered matches that of the entry. In this way any spe‐
cial initialization of the operating system, such as mounting file sys‐
tems, 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/init‐
tab.
inittab Additions
New entries can be added to /etc/inittab at any time; however, 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 forcibly 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 permit) before any further processing takes
place. In this way init can perform various cleanup and recording func‐
tions 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.
SECURITYinit uses pam(3PAM) for session management. The PAM configuration pol‐
icy, 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 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 restrict the
system milestone to svc:/milestone/single-user:default.
2
Put the system in multi-user mode. All multi-user environment ter‐
minal 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 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 usu‐
ally 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.
The service svc:/system/boot-config:default is enabled by default.
When the config/fastreboot_default property is set to true, init 6
will bypass certain firmware initialization and test steps, depend‐
ing on the specific capabilities of the system.
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 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 exam‐
ple, 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/zone‐
info.
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
setting of CMASK
LC_CTYPE
Character characterization 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 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.
/etc/svc/volatile/init.state
init state necessary to recover from failure.
/var/adm/utmpx
User access and administration information.
/var/adm/wtmpx
History of user access and administration information.
/etc/initpipe
A named pipe used for internal communication.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWcs │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOlogin(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), inittab(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 sys‐
tem 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 pro‐
gram is removed that is referenced in /etc/inittab.
NOTESinit 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 system will loop by
going to firmware and rebooting continuously.
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 initde‐
fault 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 subsequent transition to run
level 2, this file is removed.
init uses /var/run/initpipe, a named pipe, for internal communication.
The pam_unix(5) module is no longer supported. Similar functionality is
provided by pam_unix_session(5).
SunOS 5.10 24 Feb 2010 init(1M)
