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HP-UX 11i Version 3: February 2007

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inittab — script for the boot init process


The /etc/inittab file supplies the script to the boot init daemon in its role as a general process dispatcher (see init(1M)). The process that constitutes the majority of boot init's process dispatching activities is the line process /usr/sbin/getty that initiates individual terminal lines. Other processes typically dispatched by boot init are daemons and shells.

The inittab 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 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.

The entry fields are:


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).


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 init is assigned one or more run levels in which it is allowed to exist. Run levels are represented by a number in the range 0 through 6. For example, if the system is in run level 1, only those entries having a 1 in their rstate field are processed.

When boot 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). 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, 0 through 6.

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 a user init process requests them to be run (regardless of the current system run level). They differ from run levels in that boot 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 numeric run level.

Furthermore, a process started by an a, b, or c option is not killed when boot init changes levels. A process is killed only if its line in inittab is marked off in the action field, its line is deleted entirely from inittab, or boot init goes into the single-user state.


A keyword in this field tells boot init how to treat the process specified in the process field. The following actions can be specified:


Process the entry only at boot init's boot-time read of the inittab file. Boot init 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 init's run level at boot time. This action is useful for an initialization function following a hardware boot of the system.


Process the entry only at boot init's boot-time read of the inittab file. Boot init 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 init is initially invoked. Boot init 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 rstate field and using that as its initial state. If the rstate field is empty, boot init enters run level 6.

The initdefault entry cannot specify that boot init start in the single-user state. Additionally, if boot init does not find an initdefault entry in inittab, 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 (SIGTERM) and wait 20 seconds before forcibly terminating the process via the kill signal (SIGKILL). If the process is nonexistent, ignore the entry.


When boot init 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 init enters a new run level but the process is still running from a previous run level change, the process is not restarted.


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.


Execute the process associated with this entry only when boot init receives a power-fail signal (SIGPWR see signal(5)).


Execute the process associated with this entry only when boot init receives a power-fail signal (SIGPWR) and wait until it terminates before continuing any processing of inittab.


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.


Entries of this type are executed before boot init tries to access the console. It is expected that this entry will be only used to initialize devices on which boot init might attempt to obtain run level information. These entries are executed and waited for before continuing.


When boot init enters 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 boot init is in the same run level cause boot init to ignore this entry.


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 the ; #comment syntax.


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 inittab file, the /etc/utmp file can become corrupted. A corrupt /etc/utmp file can cause commands such as who to report inaccurate information.



File of processes dispatched by boot init.

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