inittab - script for init


     The file /etc/inittab controls process dispatching by  init.
     The processes most typically dispatched by init are daemons.

     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 512 characters for each  entry  are  permitted.
     Comments may be inserted in the process field using the con-
     vention for comments described in sh(1). There are no limits
     (other  than  maximum  entry  size) imposed on the number of
     entries in the inittab file. The entry fields are:

     id    One to four characters used to  uniquely  identify  an
           entry.  Do  not  use  the characters "r" or "t" as the
           first or only character in this field.  These  charac-
           ters  are  reserved  for the use of rlogin(1) and tel-

           Define the run level in which this entry is to be pro-
           cessed.  Run-levels effectively correspond to a confi-
           guration of processes in the  system.  That  is,  each
           process  spawned by init is assigned a run level(s) in
           which it is allowed  to  exist.  The  run  levels  are
           represented  by a number ranging from 0 through 6. For
           example, if the system is in run level 1,  only  those
           entries having a 1 in the 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 5-second grace period
           before being forcibly terminated by  the  kill  signal
           SIGKILL. The rstate field can define multiple run lev-
           els for a process by selecting more than one run level
           in  any  combination from 0 through 6. If no run level
           is specified, then the process is assumed to be  valid
           at all run levels 0 through 6.

           There are three other values, a, b and  c,  which  can
           appear  in  the rstate field, even though they are not
           true run levels. Entries which have  these  characters
           in the rstate field are processed only when an init or
           telinit process requests them to be run (regardless of
           the  current  run  level of the system). See init(1M).
           These 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. They are killed only if their line in
           inittab is marked off in the action field, their  line
           is  deleted  entirely  from inittab, or init goes into
           single-user state.

           Key words in this field tell init  how  to  treat  the
           process  specified  in  the process field. The actions
           recognized by init are as follows:

                 If the process does not exist,  then  start  the
                 process;  do  not wait for its termination (con-
                 tinue scanning the inittab file), and  when  the
                 process  dies, restart the process.  If the pro-
                 cess currently exists, do nothing  and  continue
                 scanning the inittab file.

           wait  When init enters the run level that matches  the
                 entry's  rstate,  start the process and wait for
                 its termination. All  subsequent  reads  of  the
                 inittab file while init is in the same run level
                 cause init to ignore this entry.

           once  When init enters a run level  that  matches  the
                 entry's  rstate,  start the process, do not wait
                 for its termination. When it dies, do  not  res-
                 tart the process. If init enters a new run level
                 and the process is still running from a previous
                 run level change, the program is not restarted.

           boot  The entry is to  be  processed  only  at  init's
                 boot-time  read  of the inittab file. init is to
                 start the process and not wait for its  termina-
                 tion; when it dies, it does not restart the pro-
                 cess. In order for this instruction to be  mean-
                 ingful,  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.

                 The entry is to be processed the first time init
                 goes  from single-user to multi-user state after
                 the system is booted. (If initdefault is set  to
                 2,  the process runs right after the boot.) init
                 starts the process, waits  for  its  termination
                 and, when it dies, does not restart the process.

                 Execute the process associated with  this  entry
                 only  when  init  receives  a power fail signal,
                 SIGPWR (see signal(3C)).

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

           off   If the process associated  with  this  entry  is
                 currently   running,  send  the  warning  signal
                 SIGTERM and wait 5 seconds before forcibly  ter-
                 minating  the  process with the kill signal SIG-
                 KILL. If the process is nonexistent, ignore  the

                 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 lev-
                 els. This instruction is used only with the a, b
                 or c values described in the rstate field.

                 An entry with this action is scanned  only  when
                 init  is initially invoked. init uses this entry
                 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,
                 this is interpreted as  0123456  and  init  will
                 enter run level 6. This will cause the system to
                 loop (it will go to firmware and reboot continu-
                 ously).  Additionally,  if init does not find an
                 initdefault entry in  inittab,  it  requests  an
                 initial run level from the user at reboot time.

                 Entries of this type are  executed  before  init
                 tries to access the console (that is, before the
                 Console Login: prompt). It is expected that this
                 entry  will  be  used only to initialize devices
                  init might try to ask the run  level  question.
                 These  entries  are  executed and init waits for
                 their completion before continuing.

           Specify a 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 legal sh
           syntax can appear in the process field.


     sh(1),  who(1),  init(1M),  ttymon(1M),  exec(2),   open(2),

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