inittab(4)inittab(4)NAMEinittab - script for the boot process
DESCRIPTION
The file supplies the script to the boot daemon in its role as a gen‐
eral process dispatcher (see init(1M)). The process that constitutes
the majority of boot process dispatching activities is the line process
that initiates individual terminal lines. Other processes typically
dispatched by boot are daemons and shells.
The file is composed of entries that are position-dependent and have
the following format:
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
by starting a "word" with a (see sh(1)). Comments for lines that spawn
are displayed by the 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 num‐
ber of entries within the file.
The entry fields are:
id A one- to four-character value used to uniquely iden‐
tify an entry. Duplicate entries cause an error mes‐
sage 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 run level in which this entry is to be
processed. Run levels correspond to a configuration
of processes in the system where each process spawned
by boot is assigned one or more run levels in which it
is allowed to exist. Run levels are represented by a
number in the range through For example, if the system
is in run level only those entries having a in their
rstate field are processed.
When boot is requested to change run levels, all pro‐
cesses that do not have an entry in the rstate field
for the target run level are sent the warning signal
and allowed a 20-second grace period before being
forcibly terminated by a kill signal You can specify
multiple run levels for a process by entering more
than one run level value in any combination. If no
run level is specified, the process is assumed to be
valid for all run levels, through
Three other values, and 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 a user process requests them
to be run (regardless of the current system run
level). They differ from run levels in that boot can
never enter "run level" or Also, a request for the
execution of any of these processes does not change
the current numeric run level.
Furthermore, a process started by an or option is not
killed when boot changes levels. A process is killed
only if its line in is marked in the action field, its
line is deleted entirely from or boot goes into the
single-user state.
action A keyword in this field tells boot how to treat the
process specified in the process field. The following
actions can be specified:
Process the entry only at boot
boot-time read of the file. Boot
starts the process, does not 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 boot run
level at boot time. This action is
useful for an initialization func‐
tion following a hardware boot of
the system.
Process the entry only at boot
boot-time read of the file. Boot
starts the process, waits for its
termination, and, when it dies, does
not restart the process.
An entry with this
action is only scanned when boot is
initially invoked. Boot uses this
entry, if it exists, to determine
which run level to enter initially.
It does this by taking the highest
run level specified in the field and
using that as its initial state. If
the rstate field is empty, boot
enters run level
The entry cannot specify that boot
start in the single-user state.
Additionally, if boot does not find
an entry in it requests an initial
run level from the user at boot
time.
If the process associated with this entry is currently
running,
send the warning signal and wait 20
seconds before forcibly terminating
the process via the kill signal If
the process is nonexistent, ignore
the entry.
When boot enters a run level that matches the
entry's rstate, start the process
and do not wait for its termination.
When it dies, do not restart the
process. If boot enters a new run
level but the process is still run‐
ning from a previous run level
change, the process is not
restarted.
This instruction is really a synonym for the
action. It is functionally identi‐
cal to but is given a different key‐
word in order to divorce its associ‐
ation with run levels. This is used
only with the or values described in
the rstate field.
Execute the process associated with this entry only
when boot
receives a power-fail signal see
signal(5)).
Execute the process associated with this entry only
when boot
receives a power-fail signal and
wait until it terminates before con‐
tinuing any processing of
If the process does not exist, start the process;
do not wait for its termination
(continue scanning the file). When
it dies, restart the process. If
the process currently exists, do
nothing and continue scanning the
file.
Entries of this type are executed before boot
tries to access the console. It is
expected that this entry will be
only used to initialize devices on
which boot might attempt to obtain
run level information. These
entries are executed and waited for
before continuing.
When boot enters the run level that matches
the entry's rstate, start the
process and wait for its termina‐
tion. Any subsequent reads of the
file while boot is in the same run
level cause boot to ignore this
entry.
process This is a command to be executed. The entire field is
prefixed with and passed to a forked as "". For this
reason, any syntax that can legally follow can appear
in the process field. Comments can be inserted by
using the syntax.
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 file, the file can
become corrupted. A corrupt file can cause commands such as to report
inaccurate information.
FILES
File of processes dispatched by boot
SEE ALSOsh(1), getty(1M), exec(2), open(2), signal(5).
inittab(4)
