HPUX inittab[4]
inittab(4) inittab(4)
NAME
inittab - script for the init process
DESCRIPTION
The inittab file supplies the script to init's role as a general
process dispatcher (see init(1M)). The process that constitutes the
majority of init's process dispatching activities is the line process
/etc/getty that initiates individual terminal lines. Other processes
typically dispatched by init are daemons and the shell.
The inittab file is composed of entries that are position-dependent
and have the following format:
id:rstate:action:process
Each entry is delimited by a newline; however, a backslash (\)
preceding a newline indicates a continuation of the entry. Up to 1024
characters per entry are permitted. Comments can be inserted in the
process field using the sh(1) convention for comments. Comments for
lines that spawn gettys are displayed by the who command (see who(1)).
It is expected that they will contain some information about the line
such as the location. There are no limits (other than maximum entry
size) imposed on the number of entries within the inittab file. Entry
fields are:
id A one- to four-character value used to uniquely
identify an entry. Duplicate entries cause an error
message to be issued, but are otherwise ignored. The
use of a four-character value to identify an entry is
strongly recommended (see WARNINGS below).
rstate Defines the runlevel in which this entry is to be
processed. Run levels correspond to a configuration of
processes in the system where each process spawned by
init is assigned a run level or run levels in which it
is allowed to exist. run levels are represented by a
number ranging from 0 through 6. For example, if the
system is in runlevel 1, only those entries having a 1
in their rstate field are processed.
When init is requested to change run levels, all
processes that do not have an entry in the rstate field
for the target run level are sent the warning signal
(SIGTERM) and allowed a 20-second grace period before
being forcibly terminated by a kill signal (SIGKILL).
The rstate field can define multiple run levels for a
process by selecting more than one run level in any
combination from 0 through 6. If no run level is
specified, the process is assumed to be valid at all
run-levels, 0 through 6.
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Three other values, a, b and c, can also appear in the
rstate field, even though they are not true run levels.
Entries having these characters in the rstate field are
processed only when the telinit (see init(1M)) process
requests them to be run (regardless of the current
system runlevel). They differ from run levels in that
init can never enter run level a, b, or c. Also, a
request for the execution of any of these processes
does not change the current run level.
Furthermore, a process started by an a, b, or c command
is not killed when init changes levels. Processes are
killed only if their line in /etc/inittab is marked off
in the action field, their line is deleted entirely
from /etc/inittab, or init goes into the Single-User
state.
action Key words in this field tell init how to treat the
process specified in the process field. Actions
recognized by init are as follows:
respawn If the process does not exist,
start the process; do not wait for
its termination (continue scanning
the inittab file). When it dies
restart the process. If the
process currently exists, do
nothing and continue scanning the
inittab file.
wait Upon init's entering the run level
that matches the entry's rstate,
start the process and wait for its
termination. Any subsequent reads
of the inittab file while init is
in the same run level cause init to
ignore this entry.
once Upon init's entering a run level
that matches the entry's rstate,
start the process; do not wait for
its termination. When it dies, do
not restart the process. If init
enters a new run level but the
process is still running from a
previous run level change, the
program is not restarted.
boot Process the entry only at init's
boot-time read of the inittab file.
init starts the process, does not
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wait for its termination, and when
it dies, does not restart the
process. In order for this
instruction to be meaningful, the
rstate should be the default or it
must match init's run level at boot
time. This action is useful for an
initialization function following a
hardware reboot of the system.
bootwait Process the entry only at init's
boot-time read of the inittab file.
init starts the process, waits for
its termination and, when it dies,
does not restart the process.
powerfail Execute the process associated with
this entry only when init receives
a power-fail signal (SIGPWR see
signal(5)).
powerwait Execute the process associated with
this entry only when init receives
a power-fail signal (SIGPWR) and
wait until it terminates before
continuing any processing of
inittab.
off If the process associated with this
entry is currently running, send
the warning signal (SIGTERM) and
wait 20 seconds before forcibly
terminating the process via the
kill signal (SIGKILL). If the
process is nonexistent, ignore the
entry.
ondemand This instruction is really a
synonym for the respawn action. It
is functionally identical to
respawn but is given a different
keyword in order to divorce its
association with run levels. This
is used only with the a, b, or c
values described in the rstate
field.
initdefault An entry with this action is only
scanned when init initially
invoked. init uses this entry, if
it exists, to determine which run
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level to enter initially. It does
this by taking the highest run
level specified in the rstate field
and using that as its initial
state. If the rstate field is
empty, this is interpreted as
0123456 causing init to enter run
level 6.
The initdefault entry cannot
specify that init start in the
Single-User state. Additionally,
if init does not find an
initdefault entry in /etc/inittab,
it requests an initial run level
from the user at reboot time.
sysinit Entries of this type are executed
before init tries to access the
console. It is expected that this
entry will be only used to
initialize devices on which init
might attempt to obtain run level
information. These entries are
executed and waited for before
continuing.
process This is a sh command to be executed. The entire
process field is prefixed with exec and passed to a
forked sh as sh -c 'exec command'. For this reason,
any sh syntax that can legally follow exec can appear
in the process field. Comments can be inserted by
using ; #comment syntax.
In the HP Clustered environment, /etc/inittab is a context-
dependent file (CDF) because different cnodes have different
initialization requirements. See cdf(4).
WARNINGS
The use of a four-character id is strongly recommended. Many pty
servers use the last two characters of the pty name as an id. If an
id chosen by a pty server collides with one used in the /etc/inittab
file, the /etc/utmp file can become corrupted. A corrupt /etc/utmp
file can cause commands such as who to report inaccurate information.
FILES
/etc/inittab
SEE ALSO
sh(1), getty(1M), exec(2), open(2), signal(5).
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