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INIT(8)                       1990			  INIT(8)



N\bNA\bAM\bME\bE
     init - process control initialization

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
     /\b/e\bet\btc\bc/\b/i\bin\bni\bit\bt

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
     _\bI_\bn_\bi_\bt is invoked inside UNIX as the last step in the boot
     procedure.  It normally then runs the automatic reboot
     sequence as described in _\br_\be_\bb_\bo_\bo_\bt(8), and if this succeeds,
     begins multi-user operation.  If the reboot fails, it com-
     mences single user operation by giving the super-user a
     shell on the console.  It is possible to pass parameters
     from the boot program to _\bi_\bn_\bi_\bt so that single user operation
     is commenced immediately.	When such single user operation
     is terminated by killing the single-user shell (i.e. by hit-
     ting ^D), _\bi_\bn_\bi_\bt runs /_\be_\bt_\bc/_\br_\bc without the reboot parameter.
     This command file performs housekeeping operations such as
     removing temporary files, mounting file systems, and start-
     ing daemons.

     In multi-user operation, _\bi_\bn_\bi_\bt'_\bs role is to create a process
     for each terminal port on which a user may log in.  To begin
     such operations, it reads the file /_\be_\bt_\bc/_\bt_\bt_\by_\bs and executes a
     command for each terminal specified in the file.  This com-
     mand will usually be /_\bu_\bs_\br/_\bl_\bi_\bb_\be_\bx_\be_\bc/_\bg_\be_\bt_\bt_\by.  _\bG_\be_\bt_\bt_\by opens and
     initializes the terminal line, reads the user's name and
     invokes _\bl_\bo_\bg_\bi_\bn to log in the user and execute the Shell.

     Ultimately the Shell will terminate because of an end-of-
     file either typed explicitly or generated as a result of
     hanging up.  The main path of _\bi_\bn_\bi_\bt, which has been waiting
     for such an event, wakes up and removes the appropriate
     entry from the file _\bu_\bt_\bm_\bp, which records current users, and
     makes an entry in /_\bv_\ba_\br/_\bl_\bo_\bg/_\bw_\bt_\bm_\bp, which maintains a history
     of logins and logouts.  The _\bw_\bt_\bm_\bp entry is made only if a
     user logged in successfully on the line.  Then the appropri-
     ate terminal is reopened and _\bg_\be_\bt_\bt_\by is reinvoked.

     _\bI_\bn_\bi_\bt catches the _\bh_\ba_\bn_\bg_\bu_\bp signal (signal SIGHUP) and inter-
     prets it to mean that the file /_\be_\bt_\bc/_\bt_\bt_\by_\bs should be read
     again.  The Shell process on each line which used to be
     active in _\bt_\bt_\by_\bs but is no longer there is terminated; a new
     process is created for each added line; lines unchanged in
     the file are undisturbed.	Thus it is possible to drop or
     add terminal lines without rebooting the system by changing
     the _\bt_\bt_\by_\bs file and sending a _\bh_\ba_\bn_\bg_\bu_\bp signal to the _\bi_\bn_\bi_\bt pro-
     cess: use `kill -HUP 1.'

     _\bI_\bn_\bi_\bt will terminate multi-user operations and resume
     single-user mode if sent a terminate (TERM) signal, i.e.
     ``kill -TERM 1''.	If there are processes outstanding which



Printed 7/27/90               June				1






INIT(8)                       1990			  INIT(8)



     are deadlocked (due to hardware or software failure), _\bi_\bn_\bi_\bt
     will not wait for them all to die (which might take for-
     ever), but will time out after 30 seconds and print a warn-
     ing message.

     _\bI_\bn_\bi_\bt will cease creating new _\bg_\be_\bt_\bt_\by's and allow the system to
     slowly die away, if it is sent a terminal stop (TSTP) sig-
     nal, i.e. ``kill -TSTP 1''.  A later hangup will resume full
     multi-user operations, or a terminate will initiate a single
     user shell.  This hook is used by _\br_\be_\bb_\bo_\bo_\bt(8) and _\bh_\ba_\bl_\bt(8).

     _\bI_\bn_\bi_\bt'_\bs role is so critical that if it dies, the system will
     reboot itself automatically.  If, at bootstrap time, the
     _\bi_\bn_\bi_\bt process cannot be located, the system will loop in user
     mode at location 0x13.

D\bDI\bIA\bAG\bGN\bNO\bOS\bST\bTI\bIC\bCS\bS
     /\b/u\bus\bsr\br/\b/l\bli\bib\bbe\bex\bxe\bec\bc/\b/g\bge\bet\btt\bty\by _\bg_\be_\bt_\bt_\by_\ba_\br_\bg_\bs f\bfa\bai\bil\bli\bin\bng\bg,\b, s\bsl\ble\bee\bep\bpi\bin\bng\bg.  A process
     being started to service a line is exiting quickly each time
     it is started.  This is often caused by a ringing or noisy
     terminal line.  _\bI_\bn_\bi_\bt _\bw_\bi_\bl_\bl _\bs_\bl_\be_\be_\bp _\bf_\bo_\br _\b3_\b0 _\bs_\be_\bc_\bo_\bn_\bd_\bs,

     W\bWA\bAR\bRN\bNI\bIN\bNG\bG:\b: S\bSo\bom\bme\bet\bth\bhi\bin\bng\bg i\bis\bs h\bhu\bun\bng\bg (\b(w\bwo\bon\bnt\bt d\bdi\bie\be)\b);\b; p\bps\bs a\bax\bxl\bl a\bad\bdv\bvi\bis\bse\bed\bd.  A
     process is hung and could not be killed when the system was
     shutting down.  This is usually caused by a process which is
     stuck in a device driver due to a persistent device error
     condition.

F\bFI\bIL\bLE\bES\bS
     /dev/console, /dev/tty*, /var/run/utmp, /var/log/wtmp,
     /etc/ttys, /etc/rc

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
     login(1), kill(1), sh(1), ttys(5), crash(8V), getty(8),
     rc(8), reboot(8), halt(8), shutdown(8)




















Printed 7/27/90               June				2