text: /* vi: set sw=4 ts=4: */
  /*
   * Mini init implementation for busybox
   *
   * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
   * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
   * Adjusted by so many folks, it's impossible to keep track.
   *
   * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   */
  //config:config INIT
  //config:	bool "init (10 kb)"
  //config:	default y
  //config:	select FEATURE_SYSLOG
  //config:	help
  //config:	init is the first program run when the system boots.
  //config:
  //config:config LINUXRC
  //config:	bool "linuxrc: support running init from initrd (not initramfs)"
  //config:	default y
  //config:	select FEATURE_SYSLOG
  //config:	help
  //config:	Legacy support for running init under the old-style initrd. Allows
  //config:	the name linuxrc to act as init, and it doesn't assume init is PID 1.
  //config:
  //config:	This does not apply to initramfs, which runs /init as PID 1 and
  //config:	requires no special support.
  //config:
  //config:config FEATURE_USE_INITTAB
  //config:	bool "Support reading an inittab file"
  //config:	default y
  //config:	depends on INIT || LINUXRC
  //config:	help
  //config:	Allow init to read an inittab file when the system boot.
  //config:
  //config:config FEATURE_KILL_REMOVED
  //config:	bool "Support killing processes that have been removed from inittab"
  //config:	default n
  //config:	depends on FEATURE_USE_INITTAB
  //config:	help
  //config:	When respawn entries are removed from inittab and a SIGHUP is
  //config:	sent to init, this option will make init kill the processes
  //config:	that have been removed.
  //config:
  //config:config FEATURE_KILL_DELAY
  //config:	int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED
  //config:	range 0 1024
  //config:	default 0
  //config:	depends on FEATURE_KILL_REMOVED
  //config:	help
  //config:	With nonzero setting, init sends TERM, forks, child waits N
  //config:	seconds, sends KILL and exits. Setting it too high is unwise
  //config:	(child will hang around for too long and could actually kill
  //config:	the wrong process!)
  //config:
  //config:config FEATURE_INIT_SCTTY
  //config:	bool "Run commands with leading dash with controlling tty"
  //config:	default y
  //config:	depends on INIT || LINUXRC
  //config:	help
  //config:	If this option is enabled, init will try to give a controlling
  //config:	tty to any command which has leading hyphen (often it's "-/bin/sh").
  //config:	More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)".
  //config:	If device attached to STDIN_FILENO can be a ctty but is not yet
  //config:	a ctty for other session, it will become this process' ctty.
  //config:	This is not the traditional init behavour, but is often what you want
  //config:	in an embedded system where the console is only accessed during
  //config:	development or for maintenance.
  //config:	NB: using cttyhack applet may work better.
  //config:
  //config:config FEATURE_INIT_SYSLOG
  //config:	bool "Enable init to write to syslog"
  //config:	default y
  //config:	depends on INIT || LINUXRC
  //config:	help
  //config:	If selected, some init messages are sent to syslog.
  //config:	Otherwise, they are sent to VT #5 if linux virtual tty is detected
  //config:	(if not, no separate logging is done).
  //config:
  //config:config FEATURE_INIT_QUIET
  //config:	bool "Be quiet on boot (no 'init started:' message)"
  //config:	default y
  //config:	depends on INIT || LINUXRC
  //config:
  //config:config FEATURE_INIT_COREDUMPS
  //config:	bool "Support dumping core for child processes (debugging only)"
  //config:	default n	# not Y because this is a debug option
  //config:	depends on INIT || LINUXRC
  //config:	help
  //config:	If this option is enabled and the file /.init_enable_core
  //config:	exists, then init will call setrlimit() to allow unlimited
  //config:	core file sizes. If this option is disabled, processes
  //config:	will not generate any core files.
  //config:
  //config:config INIT_TERMINAL_TYPE
  //config:	string "Initial terminal type"
  //config:	default "linux"
  //config:	depends on INIT || LINUXRC
  //config:	help
  //config:	This is the initial value set by init for the TERM environment
  //config:	variable. This variable is used by programs which make use of
  //config:	extended terminal capabilities.
  //config:
  //config:	Note that on Linux, init attempts to detect serial terminal and
  //config:	sets TERM to "vt102" if one is found.
  //config:
  //config:config FEATURE_INIT_MODIFY_CMDLINE
  //config:	bool "Clear init's command line"
  //config:	default y
  //config:	depends on INIT || LINUXRC
  //config:	help
  //config:	When launched as PID 1 and after parsing its arguments, init
  //config:	wipes all the arguments but argv[0] and rewrites argv[0] to
  //config:	contain only "init", so that its command line appears solely as
  //config:	"init" in tools such as ps.
  //config:	If this option is set to Y, init will keep its original behavior,
  //config:	otherwise, all the arguments including argv[0] will be preserved,
  //config:	be they parsed or ignored by init.
  //config:	The original command-line used to launch init can then be
  //config:	retrieved in /proc/1/cmdline on Linux, for example.
  
  //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
  //applet:IF_LINUXRC(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
  
  //kbuild:lib-$(CONFIG_INIT) += init.o
  //kbuild:lib-$(CONFIG_LINUXRC) += init.o
  
  #define DEBUG_SEGV_HANDLER 0
  
  #include "libbb.h"
  #include "common_bufsiz.h"
  #include <syslog.h>
  #ifdef __linux__
  # include <linux/vt.h>
  # include <sys/sysinfo.h>
  #endif
  #include "reboot.h" /* reboot() constants */
  
  #if DEBUG_SEGV_HANDLER
  # undef _GNU_SOURCE
  # define _GNU_SOURCE 1
  # undef __USE_GNU
  # define __USE_GNU 1
  # include <execinfo.h>
  # include <sys/ucontext.h>
  #endif
  
  /* Used only for sanitizing purposes in set_sane_term() below. On systems where
   * the baud rate is stored in a separate field, we can safely disable them. */
  #ifndef CBAUD
  # define CBAUD 0
  # define CBAUDEX 0
  #endif
  
  /* Was a CONFIG_xxx option. A lot of people were building
   * not fully functional init by switching it on! */
  #define DEBUG_INIT 0
  
  #define CONSOLE_NAME_SIZE 32
  
  /* Default sysinit script. */
  #ifndef INIT_SCRIPT
  # define INIT_SCRIPT  "/etc/init.d/rcS"
  #endif
  
  /* Each type of actions can appear many times. They will be
   * handled in order. RESTART is an exception, only 1st is used.
   */
  /* Start these actions first and wait for completion */
  #define SYSINIT     0x01
  /* Start these after SYSINIT and wait for completion */
  #define WAIT        0x02
  /* Start these after WAIT and *dont* wait for completion */
  #define ONCE        0x04
  /*
   * NB: while SYSINIT/WAIT/ONCE are being processed,
   * SIGHUP ("reread /etc/inittab") will be processed only after
   * each group of actions. If new inittab adds, say, a SYSINIT action,
   * it will not be run, since init is already "past SYSINIT stage".
   */
  /* Start these after ONCE are started, restart on exit */
  #define RESPAWN     0x08
  /* Like RESPAWN, but wait for <Enter> to be pressed on tty */
  #define ASKFIRST    0x10
  /*
   * Start these on SIGINT, and wait for completion.
   * Then go back to respawning RESPAWN and ASKFIRST actions.
   * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
   */
  #define CTRLALTDEL  0x20
  /*
   * Start these before killing all processes in preparation for
   * running RESTART actions or doing low-level halt/reboot/poweroff
   * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
   * Wait for completion before proceeding.
   */
  #define SHUTDOWN    0x40
  /*
   * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
   * then all processes are killed, then init exec's 1st RESTART action,
   * replacing itself by it. If no RESTART action specified,
   * SIGQUIT has no effect.
   */
  #define RESTART     0x80
  
  /* A linked list of init_actions, to be read from inittab */
  struct init_action {
  	struct init_action *next;
  	pid_t pid;
  	uint8_t action_type;
  	char terminal[CONSOLE_NAME_SIZE];
  	char command[1];
  };
  
  struct globals {
  	struct init_action *init_action_list;
  #if !ENABLE_FEATURE_INIT_SYSLOG
  	const char *log_console;
  #endif
  } FIX_ALIASING;
  #define G (*(struct globals*)bb_common_bufsiz1)
  #define INIT_G() do { \
  	setup_common_bufsiz(); \
  	IF_NOT_FEATURE_INIT_SYSLOG(G.log_console = VC_5;) \
  } while (0)
  
  enum {
  	L_LOG = 0x1,
  	L_CONSOLE = 0x2,
  };
  
  /* Print a message to the specified device.
   * "where" may be bitwise-or'd from L_LOG | L_CONSOLE
   * NB: careful, we can be called after vfork!
   */
  #define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
  static void message(int where, const char *fmt, ...)
  	__attribute__ ((format(printf, 2, 3)));
  static void message(int where, const char *fmt, ...)
  {
  	va_list arguments;
  	unsigned l;
  	char msg[128];
  
  	msg[0] = '\r';
  	va_start(arguments, fmt);
  	l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments);
  	if (l > sizeof(msg) - 2)
  		l = sizeof(msg) - 2;
  	va_end(arguments);
  
  #if ENABLE_FEATURE_INIT_SYSLOG
  	msg[l] = '\0';
  	if (where & L_LOG) {
  		/* Log the message to syslogd */
  		openlog(applet_name, 0, LOG_DAEMON);
  		/* don't print "\r" */
  		syslog(LOG_INFO, "%s", msg + 1);
  		closelog();
  	}
  	msg[l++] = '\n';
  	msg[l] = '\0';
  #else
  	msg[l++] = '\n';
  	msg[l] = '\0';
  	if (where & L_LOG) {
  		/* Take full control of the log tty, and never close it.
  		 * It's mine, all mine!  Muhahahaha! */
  		static int log_fd = -1;
  
  		if (log_fd < 0) {
  			log_fd = STDERR_FILENO;
  			if (G.log_console) {
  				log_fd = device_open(G.log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY);
  				if (log_fd < 0) {
  					bb_error_msg("can't log to %s", G.log_console);
  					where = L_CONSOLE;
  				} else {
  					close_on_exec_on(log_fd);
  				}
  			}
  		}
  		full_write(log_fd, msg, l);
  		if (log_fd == STDERR_FILENO)
  			return; /* don't print dup messages */
  	}
  #endif
  
  	if (where & L_CONSOLE) {
  		/* Send console messages to console so people will see them. */
  		full_write(STDERR_FILENO, msg, l);
  	}
  }
  
  static void console_init(void)
  {
  #ifdef VT_OPENQRY
  	int vtno;
  #endif
  	char *s;
  
  	s = getenv("CONSOLE");
  	if (!s)
  		s = getenv("console");
  #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
  	/* BSD people say their kernels do not open fd 0,1,2; they need this: */
  	if (!s)
  		s = (char*)"/dev/console";
  #endif
  	if (s) {
  		int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY);
  		if (fd >= 0) {
  			dup2(fd, STDIN_FILENO);
  			dup2(fd, STDOUT_FILENO);
  			xmove_fd(fd, STDERR_FILENO);
  		}
  		dbg_message(L_LOG, "console='%s'", s);
  	} else {
  		/* Make sure fd 0,1,2 are not closed
  		 * (so that they won't be used by future opens) */
  		bb_sanitize_stdio();
  // Users report problems
  //		/* Make sure init can't be blocked by writing to stderr */
  //		fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK);
  	}
  
  	s = getenv("TERM");
  #ifdef VT_OPENQRY
  	if (ioctl(STDIN_FILENO, VT_OPENQRY, &vtno) != 0) {
  		/* Not a linux terminal, probably serial console.
  		 * Force the TERM setting to vt102
  		 * if TERM is set to linux (the default) */
  		if (!s || strcmp(s, "linux") == 0)
  			putenv((char*)"TERM=vt102");
  # if !ENABLE_FEATURE_INIT_SYSLOG
  		G.log_console = NULL;
  # endif
  	} else
  #endif
  	if (!s)
  		putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE);
  }
  
  /* Set terminal settings to reasonable defaults.
   * NB: careful, we can be called after vfork! */
  static void set_sane_term(void)
  {
  	struct termios tty;
  
  	tcgetattr(STDIN_FILENO, &tty);
  
  	/* set control chars */
  	tty.c_cc[VINTR] = 3;	/* C-c */
  	tty.c_cc[VQUIT] = 28;	/* C-\ */
  	tty.c_cc[VERASE] = 127;	/* C-? */
  	tty.c_cc[VKILL] = 21;	/* C-u */
  	tty.c_cc[VEOF] = 4;	/* C-d */
  	tty.c_cc[VSTART] = 17;	/* C-q */
  	tty.c_cc[VSTOP] = 19;	/* C-s */
  	tty.c_cc[VSUSP] = 26;	/* C-z */
  
  #ifdef __linux__
  	/* use line discipline 0 */
  	tty.c_line = 0;
  #endif
  
  	/* Make it be sane */
  #ifndef CRTSCTS
  # define CRTSCTS 0
  #endif
  	/* added CRTSCTS to fix Debian bug 528560 */
  	tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS;
  	tty.c_cflag |= CREAD | HUPCL | CLOCAL;
  
  	/* input modes */
  	tty.c_iflag = ICRNL | IXON | IXOFF;
  
  	/* output modes */
  	tty.c_oflag = OPOST | ONLCR;
  
  	/* local modes */
  	tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN;
  
  	tcsetattr_stdin_TCSANOW(&tty);
  }
  
  /* Open the new terminal device.
   * NB: careful, we can be called after vfork! */
  static int open_stdio_to_tty(const char* tty_name)
  {
  	/* empty tty_name means "use init's tty", else... */
  	if (tty_name[0]) {
  		int fd;
  
  		close(STDIN_FILENO);
  		/* fd can be only < 0 or 0: */
  		fd = device_open(tty_name, O_RDWR);
  		if (fd) {
  			message(L_LOG | L_CONSOLE, "can't open %s: "STRERROR_FMT,
  				tty_name
  				STRERROR_ERRNO
  			);
  			return 0; /* failure */
  		}
  		dup2(STDIN_FILENO, STDOUT_FILENO);
  		dup2(STDIN_FILENO, STDERR_FILENO);
  	}
  	set_sane_term();
  	return 1; /* success */
  }
  
  static void reset_sighandlers_and_unblock_sigs(void)
  {
  	bb_signals(0
  		+ (1 << SIGUSR1)
  		+ (1 << SIGUSR2)
  		+ (1 << SIGTERM)
  		+ (1 << SIGQUIT)
  		+ (1 << SIGINT)
  		+ (1 << SIGHUP)
  		+ (1 << SIGTSTP)
  		+ (1 << SIGSTOP)
  		, SIG_DFL);
  	sigprocmask_allsigs(SIG_UNBLOCK);
  }
  
  /* Wrapper around exec:
   * Takes string.
   * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
   * Otherwise splits words on whitespace, deals with leading dash,
   * and uses plain exec().
   * NB: careful, we can be called after vfork!
   */
  static void init_exec(const char *command)
  {
  	/* +8 allows to write VLA sizes below more efficiently: */
  	unsigned command_size = strlen(command) + 8;
  	/* strlen(command) + strlen("exec ")+1: */
  	char buf[command_size];
  	/* strlen(command) / 2 + 4: */
  	char *cmd[command_size / 2];
  	int dash;
  
  	dash = (command[0] == '-' /* maybe? && command[1] == '/' */);
  	command += dash;
  
  	/* See if any special /bin/sh requiring characters are present */
  	if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
  		sprintf(buf, "exec %s", command); /* excluding "-" */
  		/* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
  		cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash);
  		cmd[1] = (char*)"-c";
  		cmd[2] = buf;
  		cmd[3] = NULL;
  		command = LIBBB_DEFAULT_LOGIN_SHELL + 1;
  	} else {
  		/* Convert command (char*) into cmd (char**, one word per string) */
  		char *word, *next;
  		int i = 0;
  		next = strcpy(buf, command - dash); /* command including "-" */
  		command = next + dash;
  		while ((word = strsep(&next, " \t")) != NULL) {
  			if (*word != '\0') { /* not two spaces/tabs together? */
  				cmd[i] = word;
  				i++;
  			}
  		}
  		cmd[i] = NULL;
  	}
  	/* If we saw leading "-", it is interactive shell.
  	 * Try harder to give it a controlling tty.
  	 */
  	if (ENABLE_FEATURE_INIT_SCTTY && dash) {
  		/* _Attempt_ to make stdin a controlling tty. */
  		ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/);
  	}
  	/* Here command never contains the dash, cmd[0] might */
  	BB_EXECVP(command, cmd);
  	message(L_LOG | L_CONSOLE, "can't run '%s': "STRERROR_FMT, command STRERROR_ERRNO);
  	/* returns if execvp fails */
  }
  
  /* Used only by run_actions */
  static pid_t run(const struct init_action *a)
  {
  	pid_t pid;
  
  	/* Careful: don't be affected by a signal in vforked child */
  	sigprocmask_allsigs(SIG_BLOCK);
  	if (BB_MMU && (a->action_type & ASKFIRST))
  		pid = fork();
  	else
  		pid = vfork();
  	if (pid < 0)
  		message(L_LOG | L_CONSOLE, "can't fork");
  	if (pid) {
  		sigprocmask_allsigs(SIG_UNBLOCK);
  		return pid; /* Parent or error */
  	}
  
  	/* Child */
  
  	/* Reset signal handlers that were set by the parent process */
  	reset_sighandlers_and_unblock_sigs();
  
  	/* Create a new session and make ourself the process group leader */
  	setsid();
  
  	/* Open the new terminal device */
  	if (!open_stdio_to_tty(a->terminal))
  		_exit(EXIT_FAILURE);
  
  	/* NB: on NOMMU we can't wait for input in child, so
  	 * "askfirst" will work the same as "respawn". */
  	if (BB_MMU && (a->action_type & ASKFIRST)) {
  		static const char press_enter[] ALIGN1 =
  #ifdef CUSTOMIZED_BANNER
  #include CUSTOMIZED_BANNER
  #endif
  			"\nPlease press Enter to activate this console. ";
  		char c;
  		/*
  		 * Save memory by not exec-ing anything large (like a shell)
  		 * before the user wants it. This is critical if swap is not
  		 * enabled and the system has low memory. Generally this will
  		 * be run on the second virtual console, and the first will
  		 * be allowed to start a shell or whatever an init script
  		 * specifies.
  		 */
  		dbg_message(L_LOG, "waiting for enter to start '%s'"
  					"(pid %d, tty '%s')\n",
  				a->command, getpid(), a->terminal);
  		full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1);
  		while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n')
  			continue;
  	}
  
  	/*
  	 * When a file named /.init_enable_core exists, setrlimit is called
  	 * before processes are spawned to set core file size as unlimited.
  	 * This is for debugging only.  Don't use this is production, unless
  	 * you want core dumps lying about....
  	 */
  	if (ENABLE_FEATURE_INIT_COREDUMPS) {
  		if (access("/.init_enable_core", F_OK) == 0) {
  			struct rlimit limit;
  			limit.rlim_cur = RLIM_INFINITY;
  			limit.rlim_max = RLIM_INFINITY;
  			setrlimit(RLIMIT_CORE, &limit);
  		}
  	}
  
  	/* Log the process name and args */
  	message(L_LOG, "starting pid %u, tty '%s': '%s'",
  			(int)getpid(), a->terminal, a->command);
  
  	/* Now run it.  The new program will take over this PID,
  	 * so nothing further in init.c should be run. */
  	init_exec(a->command);
  	/* We're still here?  Some error happened. */
  	_exit(-1);
  }
  
  static struct init_action *mark_terminated(pid_t pid)
  {
  	struct init_action *a;
  
  	if (pid > 0) {
  		update_utmp_DEAD_PROCESS(pid);
  		for (a = G.init_action_list; a; a = a->next) {
  			if (a->pid == pid) {
  				a->pid = 0;
  				return a;
  			}
  		}
  	}
  	return NULL;
  }
  
  static void waitfor(pid_t pid)
  {
  	/* waitfor(run(x)): protect against failed fork inside run() */
  	if (pid <= 0)
  		return;
  
  	/* Wait for any child (prevent zombies from exiting orphaned processes)
  	 * but exit the loop only when specified one has exited. */
  	while (1) {
  		pid_t wpid = wait(NULL);
  		mark_terminated(wpid);
  		/* Unsafe. SIGTSTP handler might have wait'ed it already */
  		/*if (wpid == pid) break;*/
  		/* More reliable: */
  		if (kill(pid, 0))
  			break;
  	}
  }
  
  /* Run all commands of a particular type */
  static void run_actions(int action_type)
  {
  	struct init_action *a;
  
  	for (a = G.init_action_list; a; a = a->next) {
  		if (!(a->action_type & action_type))
  			continue;
  		if (a->terminal[0] && access(a->terminal, R_OK | W_OK))
  			continue;
  
  		if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
  			pid_t pid = run(a);
  			if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
  				waitfor(pid);
  		}
  		if (a->action_type & (RESPAWN | ASKFIRST)) {
  			/* Only run stuff with pid == 0. If pid != 0,
  			 * it is already running
  			 */
  			if (a->pid == 0)
  				a->pid = run(a);
  		}
  	}
  }
  
  static void new_init_action(uint8_t action_type, const char *command, const char *cons)
  {
  	struct init_action *a, **nextp;
  
  	/* Scenario:
  	 * old inittab:
  	 * ::shutdown:umount -a -r
  	 * ::shutdown:swapoff -a
  	 * new inittab:
  	 * ::shutdown:swapoff -a
  	 * ::shutdown:umount -a -r
  	 * On reload, we must ensure entries end up in correct order.
  	 * To achieve that, if we find a matching entry, we move it
  	 * to the end.
  	 */
  	nextp = &G.init_action_list;
  	while ((a = *nextp) != NULL) {
  		/* Don't enter action if it's already in the list.
  		 * This prevents losing running RESPAWNs.
  		 */
  		if (strcmp(a->command, command) == 0
  		 && strcmp(a->terminal, cons) == 0
  		) {
  			/* Remove from list */
  			*nextp = a->next;
  			/* Find the end of the list */
  			while (*nextp != NULL)
  				nextp = &(*nextp)->next;
  			a->next = NULL;
  			goto append;
  		}
  		nextp = &a->next;
  	}
  
  	a = xzalloc(sizeof(*a) + strlen(command));
  
  	/* Append to the end of the list */
   append:
  	*nextp = a;
  	a->action_type = action_type;
  	strcpy(a->command, command);
  	safe_strncpy(a->terminal, cons, sizeof(a->terminal));
  	dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%x tty='%s'\n",
  		a->command, a->action_type, a->terminal);
  }
  
  /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
   * then parse_inittab() simply adds in some default
   * actions (i.e., runs INIT_SCRIPT and then starts a pair
   * of "askfirst" shells).  If CONFIG_FEATURE_USE_INITTAB
   * _is_ defined, but /etc/inittab is missing, this
   * results in the same set of default behaviors.
   */
  static void parse_inittab(void)
  {
  #if ENABLE_FEATURE_USE_INITTAB
  	char *token[4];
  	parser_t *parser = config_open2("/etc/inittab", fopen_for_read);
  
  	if (parser == NULL)
  #endif
  	{
  		/* No inittab file - set up some default behavior */
  		/* Sysinit */
  		new_init_action(SYSINIT, INIT_SCRIPT, "");
  		/* Askfirst shell on tty1-4 */
  		new_init_action(ASKFIRST, bb_default_login_shell, "");
  //TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
  		new_init_action(ASKFIRST, bb_default_login_shell, VC_2);
  		new_init_action(ASKFIRST, bb_default_login_shell, VC_3);
  		new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
  		/* Reboot on Ctrl-Alt-Del */
  		new_init_action(CTRLALTDEL, "reboot", "");
  		/* Umount all filesystems on halt/reboot */
  		new_init_action(SHUTDOWN, "umount -a -r", "");
  		/* Swapoff on halt/reboot */
  		new_init_action(SHUTDOWN, "swapoff -a", "");
  		/* Restart init when a QUIT is received */
  		new_init_action(RESTART, "init", "");
  		return;
  	}
  
  #if ENABLE_FEATURE_USE_INITTAB
  	/* optional_tty:ignored_runlevel:action:command
  	 * Delims are not to be collapsed and need exactly 4 tokens
  	 */
  	while (config_read(parser, token, 4, 0, "#:",
  				PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
  		/* order must correspond to SYSINIT..RESTART constants */
  		static const char actions[] ALIGN1 =
  			"sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
  			"ctrlaltdel\0""shutdown\0""restart\0";
  		int action;
  		char *tty = token[0];
  
  		if (!token[3]) /* less than 4 tokens */
  			goto bad_entry;
  		action = index_in_strings(actions, token[2]);
  		if (action < 0 || !token[3][0]) /* token[3]: command */
  			goto bad_entry;
  		/* turn .*TTY -> /dev/TTY */
  		if (tty[0]) {
  			tty = concat_path_file("/dev/", skip_dev_pfx(tty));
  		}
  		new_init_action(1 << action, token[3], tty);
  		if (tty[0])
  			free(tty);
  		continue;
   bad_entry:
  		message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d",
  				parser->lineno);
  	}
  	config_close(parser);
  #endif
  }
  
  static void pause_and_low_level_reboot(unsigned magic) NORETURN;
  static void pause_and_low_level_reboot(unsigned magic)
  {
  	pid_t pid;
  
  	/* Allow time for last message to reach serial console, etc */
  	sleep(1);
  
  	/* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
  	 * in linux/kernel/sys.c, which can cause the machine to panic when
  	 * the init process exits... */
  	pid = vfork();
  	if (pid == 0) { /* child */
  		reboot(magic);
  		_exit(EXIT_SUCCESS);
  	}
  	/* Used to have "while (1) sleep(1)" here.
  	 * However, in containers reboot() call is ignored, and with that loop
  	 * we would eternally sleep here - not what we want.
  	 */
  	waitpid(pid, NULL, 0);
  	sleep(1); /* paranoia */
  	_exit(EXIT_SUCCESS);
  }
  
  static void run_shutdown_and_kill_processes(void)
  {
  	/* Run everything to be run at "shutdown".  This is done _prior_
  	 * to killing everything, in case people wish to use scripts to
  	 * shut things down gracefully... */
  	run_actions(SHUTDOWN);
  
  	message(L_CONSOLE | L_LOG, "The system is going down NOW!");
  
  	/* Send signals to every process _except_ pid 1 */
  	kill(-1, SIGTERM);
  	message(L_CONSOLE, "Sent SIG%s to all processes", "TERM");
  	sync();
  	sleep(1);
  
  	kill(-1, SIGKILL);
  	message(L_CONSOLE, "Sent SIG%s to all processes", "KILL");
  	sync();
  	/*sleep(1); - callers take care about making a pause */
  }
  
  /* Signal handling by init:
   *
   * For process with PID==1, on entry kernel sets all signals to SIG_DFL
   * and unmasks all signals. However, for process with PID==1,
   * default action (SIG_DFL) on any signal is to ignore it,
   * even for special signals SIGKILL and SIGCONT.
   * Also, any signal can be caught or blocked.
   * (but SIGSTOP is still handled specially, at least in 2.6.20)
   *
   * We install two kinds of handlers, "immediate" and "delayed".
   *
   * Immediate handlers execute at any time, even while, say, sysinit
   * is running.
   *
   * Delayed handlers just set a flag variable. The variable is checked
   * in the main loop and acted upon.
   *
   * halt/poweroff/reboot and restart have immediate handlers.
   * They only traverse linked list of struct action's, never modify it,
   * this should be safe to do even in signal handler. Also they
   * never return.
   *
   * SIGSTOP and SIGTSTP have immediate handlers. They just wait
   * for SIGCONT to happen.
   *
   * SIGHUP has a delayed handler, because modifying linked list
   * of struct action's from a signal handler while it is manipulated
   * by the program may be disastrous.
   *
   * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
   * it to happen even somewhere inside "sysinit" would be a bit awkward.
   *
   * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
   * and only one will be remembered and acted upon.
   */
  
  /* The SIGPWR/SIGUSR[12]/SIGTERM handler */
  static void halt_reboot_pwoff(int sig) NORETURN;
  static void halt_reboot_pwoff(int sig)
  {
  	const char *m;
  	unsigned rb;
  
  	/* We may call run() and it unmasks signals,
  	 * including the one masked inside this signal handler.
  	 * Testcase which would start multiple reboot scripts:
  	 *  while true; do reboot; done
  	 * Preventing it:
  	 */
  	reset_sighandlers_and_unblock_sigs();
  
  	run_shutdown_and_kill_processes();
  
  	m = "halt";
  	rb = RB_HALT_SYSTEM;
  	if (sig == SIGTERM) {
  		m = "reboot";
  		rb = RB_AUTOBOOT;
  	} else if (sig == SIGUSR2) {
  		m = "poweroff";
  		rb = RB_POWER_OFF;
  	}
  	message(L_CONSOLE, "Requesting system %s", m);
  	pause_and_low_level_reboot(rb);
  	/* not reached */
  }
  
  /* Handler for QUIT - exec "restart" action,
   * else (no such action defined) do nothing */
  static void exec_restart_action(void)
  {
  	struct init_action *a;
  
  	for (a = G.init_action_list; a; a = a->next) {
  		if (!(a->action_type & RESTART))
  			continue;
  
  		/* Starting from here, we won't return.
  		 * Thus don't need to worry about preserving errno
  		 * and such.
  		 */
  
  		reset_sighandlers_and_unblock_sigs();
  
  		run_shutdown_and_kill_processes();
  
  #ifdef RB_ENABLE_CAD
  		/* Allow Ctrl-Alt-Del to reboot the system.
  		 * This is how kernel sets it up for init, we follow suit.
  		 */
  		reboot(RB_ENABLE_CAD); /* misnomer */
  #endif
  
  		if (open_stdio_to_tty(a->terminal)) {
  			dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
  			/* Theoretically should be safe.
  			 * But in practice, kernel bugs may leave
  			 * unkillable processes, and wait() may block forever.
  			 * Oh well. Hoping "new" init won't be too surprised
  			 * by having children it didn't create.
  			 */
  			//while (wait(NULL) > 0)
  			//	continue;
  			init_exec(a->command);
  		}
  		/* Open or exec failed */
  		pause_and_low_level_reboot(RB_HALT_SYSTEM);
  		/* not reached */
  	}
  }
  
  /* The SIGSTOP/SIGTSTP handler
   * NB: inside it, all signals except SIGCONT are masked
   * via appropriate setup in sigaction().
   */
  static void stop_handler(int sig UNUSED_PARAM)
  {
  	smallint saved_bb_got_signal;
  	int saved_errno;
  
  	saved_bb_got_signal = bb_got_signal;
  	saved_errno = errno;
  	signal(SIGCONT, record_signo);
  
  	while (1) {
  		pid_t wpid;
  
  		if (bb_got_signal == SIGCONT)
  			break;
  		/* NB: this can accidentally wait() for a process
  		 * which we waitfor() elsewhere! waitfor() must have
  		 * code which is resilient against this.
  		 */
  		wpid = wait_any_nohang(NULL);
  		mark_terminated(wpid);
  		sleep(1);
  	}
  
  	signal(SIGCONT, SIG_DFL);
  	errno = saved_errno;
  	bb_got_signal = saved_bb_got_signal;
  }
  
  #if ENABLE_FEATURE_USE_INITTAB
  static void reload_inittab(void)
  {
  	struct init_action *a, **nextp;
  
  	message(L_LOG, "reloading /etc/inittab");
  
  	/* Disable old entries */
  	for (a = G.init_action_list; a; a = a->next)
  		a->action_type = 0;
  
  	/* Append new entries, or modify existing entries
  	 * (incl. setting a->action_type) if cmd and device name
  	 * match new ones. End result: only entries with
  	 * a->action_type == 0 are stale.
  	 */
  	parse_inittab();
  
  #if ENABLE_FEATURE_KILL_REMOVED
  	/* Kill stale entries */
  	/* Be nice and send SIGTERM first */
  	for (a = G.init_action_list; a; a = a->next)
  		if (a->action_type == 0 && a->pid != 0)
  			kill(a->pid, SIGTERM);
  	if (CONFIG_FEATURE_KILL_DELAY) {
  		/* NB: parent will wait in NOMMU case */
  		if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
  			sleep(CONFIG_FEATURE_KILL_DELAY);
  			for (a = G.init_action_list; a; a = a->next)
  				if (a->action_type == 0 && a->pid != 0)
  					kill(a->pid, SIGKILL);
  			_exit(EXIT_SUCCESS);
  		}
  	}
  #endif
  
  	/* Remove stale entries and SYSINIT entries.
  	 * We never rerun SYSINIT entries anyway,
  	 * removing them too saves a few bytes
  	 */
  	nextp = &G.init_action_list;
  	while ((a = *nextp) != NULL) {
  		/*
  		 * Why pid == 0 check?
  		 * Process can be removed from inittab and added *later*.
  		 * If we delete its entry but process still runs,
  		 * duplicate is spawned when the entry is re-added.
  		 */
  		if ((a->action_type & ~SYSINIT) == 0 && a->pid == 0) {
  			*nextp = a->next;
  			free(a);
  		} else {
  			nextp = &a->next;
  		}
  	}
  
  	/* Not needed: */
  	/* run_actions(RESPAWN | ASKFIRST); */
  	/* - we return to main loop, which does this automagically */
  }
  #endif
  
  static int check_delayed_sigs(void)
  {
  	int sigs_seen = 0;
  
  	while (1) {
  		smallint sig = bb_got_signal;
  
  		if (!sig)
  			return sigs_seen;
  		bb_got_signal = 0;
  		sigs_seen = 1;
  #if ENABLE_FEATURE_USE_INITTAB
  		if (sig == SIGHUP)
  			reload_inittab();
  #endif
  		if (sig == SIGINT)
  			run_actions(CTRLALTDEL);
  		if (sig == SIGQUIT) {
  			exec_restart_action();
  			/* returns only if no restart action defined */
  		}
  		if ((1 << sig) & (0
  #ifdef SIGPWR
  		    + (1 << SIGPWR)
  #endif
  		    + (1 << SIGUSR1)
  		    + (1 << SIGUSR2)
  		    + (1 << SIGTERM)
  		)) {
  			halt_reboot_pwoff(sig);
  		}
  	}
  }
  
  #if DEBUG_SEGV_HANDLER
  static
  void handle_sigsegv(int sig, siginfo_t *info, void *ucontext)
  {
  	long ip;
  	ucontext_t *uc;
  
  	uc = ucontext;
  	ip = uc->uc_mcontext.gregs[REG_EIP];
  	fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n",
  			sig,
  			/* this is void*, but using %p would print "(null)"
  			 * even for ptrs which are not exactly 0, but, say, 0x123:
  			 */
  			(long)info->si_addr,
  			ip);
  	{
  		/* glibc extension */
  		void *array[50];
  		int size;
  		size = backtrace(array, 50);
  		backtrace_symbols_fd(array, size, 2);
  	}
  	for (;;) sleep(9999);
  }
  #endif
  
  static void sleep_much(void)
  {
          sleep(30 * 24*60*60);
  }
  
  int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  int init_main(int argc UNUSED_PARAM, char **argv)
  {
  	INIT_G();
  
  	if (argv[1] && strcmp(argv[1], "-q") == 0) {
  		return kill(1, SIGHUP);
  	}
  
  #if DEBUG_SEGV_HANDLER
  	{
  		struct sigaction sa;
  		memset(&sa, 0, sizeof(sa));
  		sa.sa_sigaction = handle_sigsegv;
  		sa.sa_flags = SA_SIGINFO;
  		sigaction(SIGSEGV, &sa, NULL);
  		sigaction(SIGILL, &sa, NULL);
  		sigaction(SIGFPE, &sa, NULL);
  		sigaction(SIGBUS, &sa, NULL);
  	}
  #endif
  
  	if (!DEBUG_INIT) {
  		/* Some users send poweroff signals to init VERY early.
  		 * To handle this, mask signals early,
  		 * and unmask them only after signal handlers are installed.
  		 */
  		sigprocmask_allsigs(SIG_BLOCK);
  
  		/* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
  		if (getpid() != 1
  		 && (!ENABLE_LINUXRC || applet_name[0] != 'l') /* not linuxrc? */
  		) {
  			bb_error_msg_and_die("must be run as PID 1");
  		}
  #ifdef RB_DISABLE_CAD
  		/* Turn off rebooting via CTL-ALT-DEL - we get a
  		 * SIGINT on CAD so we can shut things down gracefully... */
  		reboot(RB_DISABLE_CAD); /* misnomer */
  #endif
  	}
  
  	/* If, say, xmalloc would ever die, we don't want to oops kernel
  	 * by exiting.
  	 * NB: we set die_func *after* PID 1 check and bb_show_usage.
  	 * Otherwise, for example, "init u" ("please rexec yourself"
  	 * command for sysvinit) will show help text (which isn't too bad),
  	 * *and sleep forever* (which is bad!)
  	 */
  	die_func = sleep_much;
  
  	/* Figure out where the default console should be */
  	console_init();
  	set_sane_term();
  	xchdir("/");
  	setsid();
  
  	/* Make sure environs is set to something sane */
  	putenv((char *) "HOME=/");
  	putenv((char *) bb_PATH_root_path);
  	putenv((char *) "SHELL=/bin/sh");
  	putenv((char *) "USER=root"); /* needed? why? */
  
  	if (argv[1])
  		xsetenv("RUNLEVEL", argv[1]);
  
  #if !ENABLE_FEATURE_INIT_QUIET
  	/* Hello world */
  	message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
  #endif
  
  	/* Check if we are supposed to be in single user mode */
  	if (argv[1]
  	 && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
  	) {
  		/* ??? shouldn't we set RUNLEVEL="b" here? */
  		/* Start a shell on console */
  		new_init_action(RESPAWN, bb_default_login_shell, "");
  	} else {
  		/* Not in single user mode - see what inittab says */
  
  		/* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
  		 * then parse_inittab() simply adds in some default
  		 * actions (i.e., INIT_SCRIPT and a pair
  		 * of "askfirst" shells) */
  		parse_inittab();
  	}
  
  #if ENABLE_SELINUX
  	if (getenv("SELINUX_INIT") == NULL) {
  		int enforce = 0;
  
  		putenv((char*)"SELINUX_INIT=YES");
  		if (selinux_init_load_policy(&enforce) == 0) {
  			BB_EXECVP(argv[0], argv);
  		} else if (enforce > 0) {
  			/* SELinux in enforcing mode but load_policy failed */
  			message(L_CONSOLE, "can't load SELinux Policy. "
  				"Machine is in enforcing mode. Halting now.");
  			return EXIT_FAILURE;
  		}
  	}
  #endif
  
  	if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE) {
  		/* Make the command line just say "init"  - that's all, nothing else */
  		strncpy(argv[0], "init", strlen(argv[0]));
  		/* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
  		while (*++argv)
  			nuke_str(*argv);
  	}
  
  	/* Set up signal handlers */
  	if (!DEBUG_INIT) {
  		struct sigaction sa;
  
  		/* Stop handler must allow only SIGCONT inside itself */
  		memset(&sa, 0, sizeof(sa));
  		sigfillset(&sa.sa_mask);
  		sigdelset(&sa.sa_mask, SIGCONT);
  		sa.sa_handler = stop_handler;
  		/* NB: sa_flags doesn't have SA_RESTART.
  		 * It must be able to interrupt wait().
  		 */
  		sigaction_set(SIGTSTP, &sa); /* pause */
  		/* Does not work as intended, at least in 2.6.20.
  		 * SIGSTOP is simply ignored by init:
  		 */
  		sigaction_set(SIGSTOP, &sa); /* pause */
  
  		/* These signals must interrupt wait(),
  		 * setting handler without SA_RESTART flag.
  		 */
  		bb_signals_recursive_norestart(0
  			+ (1 << SIGINT)  /* Ctrl-Alt-Del */
  			+ (1 << SIGQUIT) /* re-exec another init */
  #ifdef SIGPWR
  			+ (1 << SIGPWR)  /* halt */
  #endif
  			+ (1 << SIGUSR1) /* halt */
  			+ (1 << SIGTERM) /* reboot */
  			+ (1 << SIGUSR2) /* poweroff */
  #if ENABLE_FEATURE_USE_INITTAB
  			+ (1 << SIGHUP)  /* reread /etc/inittab */
  #endif
  			, record_signo);
  
  		sigprocmask_allsigs(SIG_UNBLOCK);
  	}
  
  	/* Now run everything that needs to be run */
  	/* First run the sysinit command */
  	run_actions(SYSINIT);
  	check_delayed_sigs();
  	/* Next run anything that wants to block */
  	run_actions(WAIT);
  	check_delayed_sigs();
  	/* Next run anything to be run only once */
  	run_actions(ONCE);
  
  	/* Now run the looping stuff for the rest of forever.
  	 */
  	while (1) {
  		int maybe_WNOHANG;
  
  		maybe_WNOHANG = check_delayed_sigs();
  
  		/* (Re)run the respawn/askfirst stuff */
  		run_actions(RESPAWN | ASKFIRST);
  		maybe_WNOHANG |= check_delayed_sigs();
  
  		/* Don't consume all CPU time - sleep a bit */
  		sleep(1);
  		maybe_WNOHANG |= check_delayed_sigs();
  
  		/* Wait for any child process(es) to exit.
  		 *
  		 * If check_delayed_sigs above reported that a signal
  		 * was caught, wait will be nonblocking. This ensures
  		 * that if SIGHUP has reloaded inittab, respawn and askfirst
  		 * actions will not be delayed until next child death.
  		 */
  		if (maybe_WNOHANG)
  			maybe_WNOHANG = WNOHANG;
  		while (1) {
  			pid_t wpid;
  			struct init_action *a;
  
  			/* If signals happen _in_ the wait, they interrupt it,
  			 * bb_signals_recursive_norestart set them up that way
  			 */
  			wpid = waitpid(-1, NULL, maybe_WNOHANG);
  			if (wpid <= 0)
  				break;
  
  			a = mark_terminated(wpid);
  			if (a) {
  				message(L_LOG, "process '%s' (pid %d) exited. "
  						"Scheduling for restart.",
  						a->command, wpid);
  			}
  			/* See if anyone else is waiting to be reaped */
  			maybe_WNOHANG = WNOHANG;
  		}
  	} /* while (1) */
  }
  
  //usage:#define linuxrc_trivial_usage NOUSAGE_STR
  //usage:#define linuxrc_full_usage ""
  
  //usage:#define init_trivial_usage
  //usage:       ""
  //usage:#define init_full_usage "\n\n"
  //usage:       "Init is the first process started during boot. It never exits."
  //usage:	IF_FEATURE_USE_INITTAB(
  //usage:   "\n""It (re)spawns children according to /etc/inittab."
  //usage:	)
  //usage:	IF_NOT_FEATURE_USE_INITTAB(
  //usage:   "\n""This version of init doesn't use /etc/inittab,"
  //usage:   "\n""has fixed set of processed to run."
  //usage:	)
  //usage:
  //usage:#define init_notes_usage
  //usage:	"This version of init is designed to be run only by the kernel.\n"
  //usage:	"\n"
  //usage:	"BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
  //usage:	"the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
  //usage:	"runlevels, use sysvinit.\n"
  //usage:	"\n"
  //usage:	"BusyBox init works just fine without an inittab. If no inittab is found,\n"
  //usage:	"it has the following default behavior:\n"
  //usage:	"\n"
  //usage:	"	::sysinit:/etc/init.d/rcS\n"
  //usage:	"	::askfirst:/bin/sh\n"
  //usage:	"	::ctrlaltdel:/sbin/reboot\n"
  //usage:	"	::shutdown:/sbin/swapoff -a\n"
  //usage:	"	::shutdown:/bin/umount -a -r\n"
  //usage:	"	::restart:/sbin/init\n"
  //usage:	"	tty2::askfirst:/bin/sh\n"
  //usage:	"	tty3::askfirst:/bin/sh\n"
  //usage:	"	tty4::askfirst:/bin/sh\n"
  //usage:	"\n"
  //usage:	"If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
  //usage:	"\n"
  //usage:	"	<id>:<runlevels>:<action>:<process>\n"
  //usage:	"\n"
  //usage:	"	<id>:\n"
  //usage:	"\n"
  //usage:	"		WARNING: This field has a non-traditional meaning for BusyBox init!\n"
  //usage:	"		The id field is used by BusyBox init to specify the controlling tty for\n"
  //usage:	"		the specified process to run on. The contents of this field are\n"
  //usage:	"		appended to \"/dev/\" and used as-is. There is no need for this field to\n"
  //usage:	"		be unique, although if it isn't you may have strange results. If this\n"
  //usage:	"		field is left blank, then the init's stdin/out will be used.\n"
  //usage:	"\n"
  //usage:	"	<runlevels>:\n"
  //usage:	"\n"
  //usage:	"		The runlevels field is completely ignored.\n"
  //usage:	"\n"
  //usage:	"	<action>:\n"
  //usage:	"\n"
  //usage:	"		Valid actions include: sysinit, respawn, askfirst, wait,\n"
  //usage:	"		once, restart, ctrlaltdel, and shutdown.\n"
  //usage:	"\n"
  //usage:	"		The available actions can be classified into two groups: actions\n"
  //usage:	"		that are run only once, and actions that are re-run when the specified\n"
  //usage:	"		process exits.\n"
  //usage:	"\n"
  //usage:	"		Run only-once actions:\n"
  //usage:	"\n"
  //usage:	"			'sysinit' is the first item run on boot. init waits until all\n"
  //usage:	"			sysinit actions are completed before continuing. Following the\n"
  //usage:	"			completion of all sysinit actions, all 'wait' actions are run.\n"
  //usage:	"			'wait' actions, like 'sysinit' actions, cause init to wait until\n"
  //usage:	"			the specified task completes. 'once' actions are asynchronous,\n"
  //usage:	"			therefore, init does not wait for them to complete. 'restart' is\n"
  //usage:	"			the action taken to restart the init process. By default this should\n"
  //usage:	"			simply run /sbin/init, but can be a script which runs pivot_root or it\n"
  //usage:	"			can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
  //usage:	"			actions are run when the system detects that someone on the system\n"
  //usage:	"			console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
  //usage:	"			wants to run 'reboot' at this point to cause the system to reboot.\n"
  //usage:	"			Finally the 'shutdown' action specifies the actions to taken when\n"
  //usage:	"			init is told to reboot. Unmounting filesystems and disabling swap\n"
  //usage:	"			is a very good here.\n"
  //usage:	"\n"
  //usage:	"		Run repeatedly actions:\n"
  //usage:	"\n"
  //usage:	"			'respawn' actions are run after the 'once' actions. When a process\n"
  //usage:	"			started with a 'respawn' action exits, init automatically restarts\n"
  //usage:	"			it. Unlike sysvinit, BusyBox init does not stop processes from\n"
  //usage:	"			respawning out of control. The 'askfirst' actions acts just like\n"
  //usage:	"			respawn, except that before running the specified process it\n"
  //usage:	"			displays the line \"Please press Enter to activate this console.\"\n"
  //usage:	"			and then waits for the user to press enter before starting the\n"
  //usage:	"			specified process.\n"
  //usage:	"\n"
  //usage:	"		Unrecognized actions (like initdefault) will cause init to emit an\n"
  //usage:	"		error message, and then go along with its business. All actions are\n"
  //usage:	"		run in the order they appear in /etc/inittab.\n"
  //usage:	"\n"
  //usage:	"	<process>:\n"
  //usage:	"\n"
  //usage:	"		Specifies the process to be executed and its command line.\n"
  //usage:	"\n"
  //usage:	"Example /etc/inittab file:\n"
  //usage:	"\n"
  //usage:	"	# This is run first except when booting in single-user mode\n"
  //usage:	"	#\n"
  //usage:	"	::sysinit:/etc/init.d/rcS\n"
  //usage:	"	\n"
  //usage:	"	# /bin/sh invocations on selected ttys\n"
  //usage:	"	#\n"
  //usage:	"	# Start an \"askfirst\" shell on the console (whatever that may be)\n"
  //usage:	"	::askfirst:-/bin/sh\n"
  //usage:	"	# Start an \"askfirst\" shell on /dev/tty2-4\n"
  //usage:	"	tty2::askfirst:-/bin/sh\n"
  //usage:	"	tty3::askfirst:-/bin/sh\n"
  //usage:	"	tty4::askfirst:-/bin/sh\n"
  //usage:	"	\n"
  //usage:	"	# /sbin/getty invocations for selected ttys\n"
  //usage:	"	#\n"
  //usage:	"	tty4::respawn:/sbin/getty 38400 tty4\n"
  //usage:	"	tty5::respawn:/sbin/getty 38400 tty5\n"
  //usage:	"	\n"
  //usage:	"	\n"
  //usage:	"	# Example of how to put a getty on a serial line (for a terminal)\n"
  //usage:	"	#\n"
  //usage:	"	#::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
  //usage:	"	#::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
  //usage:	"	#\n"
  //usage:	"	# Example how to put a getty on a modem line\n"
  //usage:	"	#::respawn:/sbin/getty 57600 ttyS2\n"
  //usage:	"	\n"
  //usage:	"	# Stuff to do when restarting the init process\n"
  //usage:	"	::restart:/sbin/init\n"
  //usage:	"	\n"
  //usage:	"	# Stuff to do before rebooting\n"
  //usage:	"	::ctrlaltdel:/sbin/reboot\n"
  //usage:	"	::shutdown:/bin/umount -a -r\n"
  //usage:	"	::shutdown:/sbin/swapoff -a\n"
  