141 lines
3.3 KiB
Groff
141 lines
3.3 KiB
Groff
.TH INIT 8
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.SH NAME
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init \- grandparent of all processes
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.SH DESCRIPTION
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The first program started by MINIX 3 is
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.BR init .
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The actions performed by
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.B init
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can be summarized by this pseudo shell program:
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.RS
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.nf
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.if t .ft C
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# Open 0, 1, 2.
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exec </dev/null >/dev/log 2>&1
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# Run the system initialization script.
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sh /etc/rc $bootopts
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>/etc/utmp
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echo reboot >>/usr/adm/wtmp
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while :; do
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# Wait for a process to exit, but don't always block.
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wait
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# Record logout. (Not in this dumb way, of course.)
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if "pid is in my tables" $pid
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then
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echo "logout $pid" >/etc/utmp
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echo "logout $pid" >>/usr/adm/wtmp
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fi
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# Start a new session.
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while read line type getty init
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do
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if idle $line
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then
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$init ... <$tty >$tty
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$getty <$tty >$tty 2>&1 &
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pid=$!
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"add pid to tables" $pid
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echo "login $line $pid" >/etc/utmp
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echo "login $line $pid" >>/usr/adm/wtmp
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fi
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done < /dev/ttytab
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done
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.if t .ft R
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.fi
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.RE
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The first action of
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.B init
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is to run
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.B /etc/rc
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to initialize the system as described in
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.BR boot (8).
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.B Init
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then enters its main loop where it waits for processes to exit, and starts
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processes on each enabled terminal line. The file
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.B /etc/ttytab
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contains a list of terminal devices, their terminal types, the program to
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execute on them to allow one to login (usually
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.BR getty (8)),
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and the program to execute first to initialize the line (usually
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.BR stty (1)).
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These fields may be left out to indicate that a line is disabled or that
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initialization is not necessary. The commands are searched using the path
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.BR /sbin:/bin:/usr/sbin:/usr/bin .
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.PP
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.B Init
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accepts several signals that must be sent to process id 1. (It is the first
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process, so natually its process id is 1.) The signals are:
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.TP
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.B SIGHUP
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When receiving a hangup signal,
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.B init
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will forget about errors and rescan
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.B ttytab
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for processes to execute.
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.B Init
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normally rescans
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.B ttytab
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each time it feels the need to respawn a process, so the hangup signal is only
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needed if a line has been shut down, or after a terminate signal. Note
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that after turning a line off you will have to kill the process running on
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that line manually,
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.B init
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doesn't do that for you.
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.TP
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.B SIGTERM
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Normally sent by programs that halt or reboot MINIX 3. Causes
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.B init
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to stop spawning new processes.
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.TP
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.B SIGABRT
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Sent by the keyboard driver when the
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.B CTRL-ALT-DEL
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key combination is typed. Causes
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.B init
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to run the
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.B shutdown
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command. A second abort signal makes
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.B init
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halt the system directly with a system call. The keyboard driver halts the
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system, without a sync, after the third CTRL-ALT-DEL.
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.SS "MINIX 3 vs. Minix-vmd"
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There are a few differences between standard MINIX 3 and Minix-vmd on how
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.B init
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is run. The
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.B /etc/rc
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file is executed under standard MINIX 3 with input connected to
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.BR /dev/console ,
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but under Minix-vmd this is still
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.BR /dev/null .
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This means that under Minix-vmd processes must be reconnected to
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.B /dev/console
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with the
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.BR intr (8)
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program if they need user interaction.
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Minix-vmd passes the value of the
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.B bootopts
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boot variable to /etc/rc. Standard MINIX 3 does not.
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.SH FILES
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.TP 25n
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.B /etc/ttytab
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List of terminals devices.
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.TP
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.B /etc/utmp
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List of currently logged in users.
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.TP
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.B /usr/adm/wtmp
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Login/logout history.
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.SH "SEE ALSO"
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.BR ttytab (5),
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.BR utmp (5),
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.BR getty (8),
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.BR stty (1),
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.BR boot (8).
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.SH AUTHOR
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Kees J. Bot (kjb@cs.vu.nl)
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