1 /* vi: set sw=4 ts=4: */
3 * Mini init implementation for busybox
5 * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>.
6 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
7 * Adjusted by so many folks, it's impossible to keep track.
9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
15 //config: select FEATURE_SYSLOG
17 //config: init is the first program run when the system boots.
19 //config:config FEATURE_USE_INITTAB
20 //config: bool "Support reading an inittab file"
22 //config: depends on INIT
24 //config: Allow init to read an inittab file when the system boot.
26 //config:config FEATURE_KILL_REMOVED
27 //config: bool "Support killing processes that have been removed from inittab"
29 //config: depends on FEATURE_USE_INITTAB
31 //config: When respawn entries are removed from inittab and a SIGHUP is
32 //config: sent to init, this option will make init kill the processes
33 //config: that have been removed.
35 //config:config FEATURE_KILL_DELAY
36 //config: int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED
37 //config: range 0 1024
39 //config: depends on FEATURE_KILL_REMOVED
41 //config: With nonzero setting, init sends TERM, forks, child waits N
42 //config: seconds, sends KILL and exits. Setting it too high is unwise
43 //config: (child will hang around for too long and could actually kill
44 //config: the wrong process!)
46 //config:config FEATURE_INIT_SCTTY
47 //config: bool "Run commands with leading dash with controlling tty"
49 //config: depends on INIT
51 //config: If this option is enabled, init will try to give a controlling
52 //config: tty to any command which has leading hyphen (often it's "-/bin/sh").
53 //config: More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)".
54 //config: If device attached to STDIN_FILENO can be a ctty but is not yet
55 //config: a ctty for other session, it will become this process' ctty.
56 //config: This is not the traditional init behavour, but is often what you want
57 //config: in an embedded system where the console is only accessed during
58 //config: development or for maintenance.
59 //config: NB: using cttyhack applet may work better.
61 //config:config FEATURE_INIT_SYSLOG
62 //config: bool "Enable init to write to syslog"
64 //config: depends on INIT
66 //config:config FEATURE_EXTRA_QUIET
67 //config: bool "Be _extra_ quiet on boot"
69 //config: depends on INIT
71 //config: Prevent init from logging some messages to the console during boot.
73 //config:config FEATURE_INIT_COREDUMPS
74 //config: bool "Support dumping core for child processes (debugging only)"
76 //config: depends on INIT
78 //config: If this option is enabled and the file /.init_enable_core
79 //config: exists, then init will call setrlimit() to allow unlimited
80 //config: core file sizes. If this option is disabled, processes
81 //config: will not generate any core files.
83 //config:config FEATURE_INITRD
84 //config: bool "Support running init from within an initrd (not initramfs)"
86 //config: depends on INIT
88 //config: Legacy support for running init under the old-style initrd. Allows
89 //config: the name linuxrc to act as init, and it doesn't assume init is PID 1.
91 //config: This does not apply to initramfs, which runs /init as PID 1 and
92 //config: requires no special support.
94 //config:config INIT_TERMINAL_TYPE
95 //config: string "Initial terminal type"
96 //config: default "linux"
97 //config: depends on INIT
99 //config: This is the initial value set by init for the TERM environment
100 //config: variable. This variable is used by programs which make use of
101 //config: extended terminal capabilities.
103 //config: Note that on Linux, init attempts to detect serial terminal and
104 //config: sets TERM to "vt102" if one is found.
106 //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
107 //applet:IF_FEATURE_INITRD(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
109 //kbuild:lib-$(CONFIG_INIT) += init.o
111 #define DEBUG_SEGV_HANDLER 0
116 #include <sys/resource.h>
118 # include <linux/vt.h>
119 # include <sys/sysinfo.h>
121 #include "reboot.h" /* reboot() constants */
123 #if DEBUG_SEGV_HANDLER
125 # define _GNU_SOURCE 1
128 # include <execinfo.h>
129 # include <sys/ucontext.h>
132 /* Used only for sanitizing purposes in set_sane_term() below. On systems where
133 * the baud rate is stored in a separate field, we can safely disable them. */
139 /* Was a CONFIG_xxx option. A lot of people were building
140 * not fully functional init by switching it on! */
143 #define CONSOLE_NAME_SIZE 32
145 /* Default sysinit script. */
147 # define INIT_SCRIPT "/etc/init.d/rcS"
150 /* Each type of actions can appear many times. They will be
151 * handled in order. RESTART is an exception, only 1st is used.
153 /* Start these actions first and wait for completion */
155 /* Start these after SYSINIT and wait for completion */
157 /* Start these after WAIT and *dont* wait for completion */
160 * NB: while SYSINIT/WAIT/ONCE are being processed,
161 * SIGHUP ("reread /etc/inittab") will be processed only after
162 * each group of actions. If new inittab adds, say, a SYSINIT action,
163 * it will not be run, since init is already "past SYSINIT stage".
165 /* Start these after ONCE are started, restart on exit */
167 /* Like RESPAWN, but wait for <Enter> to be pressed on tty */
168 #define ASKFIRST 0x10
170 * Start these on SIGINT, and wait for completion.
171 * Then go back to respawning RESPAWN and ASKFIRST actions.
172 * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
174 #define CTRLALTDEL 0x20
176 * Start these before killing all processes in preparation for
177 * running RESTART actions or doing low-level halt/reboot/poweroff
178 * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
179 * Wait for completion before proceeding.
181 #define SHUTDOWN 0x40
183 * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
184 * then all processes are killed, then init exec's 1st RESTART action,
185 * replacing itself by it. If no RESTART action specified,
186 * SIGQUIT has no effect.
191 /* A linked list of init_actions, to be read from inittab */
193 struct init_action *next;
196 char terminal[CONSOLE_NAME_SIZE];
200 static struct init_action *init_action_list = NULL;
202 static const char *log_console = VC_5;
209 /* Print a message to the specified device.
210 * "where" may be bitwise-or'd from L_LOG | L_CONSOLE
211 * NB: careful, we can be called after vfork!
213 #define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
214 static void message(int where, const char *fmt, ...)
215 __attribute__ ((format(printf, 2, 3)));
216 static void message(int where, const char *fmt, ...)
223 va_start(arguments, fmt);
224 l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments);
225 if (l > sizeof(msg) - 2)
229 #if ENABLE_FEATURE_INIT_SYSLOG
232 /* Log the message to syslogd */
233 openlog(applet_name, 0, LOG_DAEMON);
234 /* don't print "\r" */
235 syslog(LOG_INFO, "%s", msg + 1);
242 static int log_fd = -1;
246 /* Take full control of the log tty, and never close it.
247 * It's mine, all mine! Muhahahaha! */
250 log_fd = STDERR_FILENO;
252 log_fd = device_open(log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY);
254 bb_error_msg("can't log to %s", log_console);
257 close_on_exec_on(log_fd);
262 full_write(log_fd, msg, l);
263 if (log_fd == STDERR_FILENO)
264 return; /* don't print dup messages */
269 if (where & L_CONSOLE) {
270 /* Send console messages to console so people will see them. */
271 full_write(STDERR_FILENO, msg, l);
275 static void console_init(void)
282 s = getenv("CONSOLE");
284 s = getenv("console");
286 int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY);
288 dup2(fd, STDIN_FILENO);
289 dup2(fd, STDOUT_FILENO);
290 xmove_fd(fd, STDERR_FILENO);
292 dbg_message(L_LOG, "console='%s'", s);
294 /* Make sure fd 0,1,2 are not closed
295 * (so that they won't be used by future opens) */
297 // Users report problems
298 // /* Make sure init can't be blocked by writing to stderr */
299 // fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK);
304 if (ioctl(STDIN_FILENO, VT_OPENQRY, &vtno) != 0) {
305 /* Not a linux terminal, probably serial console.
306 * Force the TERM setting to vt102
307 * if TERM is set to linux (the default) */
308 if (!s || strcmp(s, "linux") == 0)
309 putenv((char*)"TERM=vt102");
310 if (!ENABLE_FEATURE_INIT_SYSLOG)
315 putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE);
318 /* Set terminal settings to reasonable defaults.
319 * NB: careful, we can be called after vfork! */
320 static void set_sane_term(void)
324 tcgetattr(STDIN_FILENO, &tty);
326 /* set control chars */
327 tty.c_cc[VINTR] = 3; /* C-c */
328 tty.c_cc[VQUIT] = 28; /* C-\ */
329 tty.c_cc[VERASE] = 127; /* C-? */
330 tty.c_cc[VKILL] = 21; /* C-u */
331 tty.c_cc[VEOF] = 4; /* C-d */
332 tty.c_cc[VSTART] = 17; /* C-q */
333 tty.c_cc[VSTOP] = 19; /* C-s */
334 tty.c_cc[VSUSP] = 26; /* C-z */
337 /* use line discipline 0 */
341 /* Make it be sane */
345 /* added CRTSCTS to fix Debian bug 528560 */
346 tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS;
347 tty.c_cflag |= CREAD | HUPCL | CLOCAL;
350 tty.c_iflag = ICRNL | IXON | IXOFF;
353 tty.c_oflag = OPOST | ONLCR;
356 tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN;
358 tcsetattr_stdin_TCSANOW(&tty);
361 /* Open the new terminal device.
362 * NB: careful, we can be called after vfork! */
363 static int open_stdio_to_tty(const char* tty_name)
365 /* empty tty_name means "use init's tty", else... */
370 /* fd can be only < 0 or 0: */
371 fd = device_open(tty_name, O_RDWR);
373 message(L_LOG | L_CONSOLE, "can't open %s: %s",
374 tty_name, strerror(errno));
375 return 0; /* failure */
377 dup2(STDIN_FILENO, STDOUT_FILENO);
378 dup2(STDIN_FILENO, STDERR_FILENO);
381 return 1; /* success */
384 static void reset_sighandlers_and_unblock_sigs(void)
396 sigprocmask_allsigs(SIG_UNBLOCK);
399 /* Wrapper around exec:
401 * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
402 * Otherwise splits words on whitespace, deals with leading dash,
403 * and uses plain exec().
404 * NB: careful, we can be called after vfork!
406 static void init_exec(const char *command)
408 /* +8 allows to write VLA sizes below more efficiently: */
409 unsigned command_size = strlen(command) + 8;
410 /* strlen(command) + strlen("exec ")+1: */
411 char buf[command_size];
412 /* strlen(command) / 2 + 4: */
413 char *cmd[command_size / 2];
416 dash = (command[0] == '-' /* maybe? && command[1] == '/' */);
419 /* See if any special /bin/sh requiring characters are present */
420 if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
421 sprintf(buf, "exec %s", command); /* excluding "-" */
422 /* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
423 cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash);
424 cmd[1] = (char*)"-c";
427 command = LIBBB_DEFAULT_LOGIN_SHELL + 1;
429 /* Convert command (char*) into cmd (char**, one word per string) */
432 next = strcpy(buf, command - dash); /* command including "-" */
433 command = next + dash;
434 while ((word = strsep(&next, " \t")) != NULL) {
435 if (*word != '\0') { /* not two spaces/tabs together? */
442 /* If we saw leading "-", it is interactive shell.
443 * Try harder to give it a controlling tty.
445 if (ENABLE_FEATURE_INIT_SCTTY && dash) {
446 /* _Attempt_ to make stdin a controlling tty. */
447 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/);
449 /* Here command never contains the dash, cmd[0] might */
450 BB_EXECVP(command, cmd);
451 message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno));
452 /* returns if execvp fails */
455 /* Used only by run_actions */
456 static pid_t run(const struct init_action *a)
460 /* Careful: don't be affected by a signal in vforked child */
461 sigprocmask_allsigs(SIG_BLOCK);
462 if (BB_MMU && (a->action_type & ASKFIRST))
467 message(L_LOG | L_CONSOLE, "can't fork");
469 sigprocmask_allsigs(SIG_UNBLOCK);
470 return pid; /* Parent or error */
475 /* Reset signal handlers that were set by the parent process */
476 reset_sighandlers_and_unblock_sigs();
478 /* Create a new session and make ourself the process group leader */
481 /* Open the new terminal device */
482 if (!open_stdio_to_tty(a->terminal))
485 /* NB: on NOMMU we can't wait for input in child, so
486 * "askfirst" will work the same as "respawn". */
487 if (BB_MMU && (a->action_type & ASKFIRST)) {
488 static const char press_enter[] ALIGN1 =
489 #ifdef CUSTOMIZED_BANNER
490 #include CUSTOMIZED_BANNER
492 "\nPlease press Enter to activate this console. ";
495 * Save memory by not exec-ing anything large (like a shell)
496 * before the user wants it. This is critical if swap is not
497 * enabled and the system has low memory. Generally this will
498 * be run on the second virtual console, and the first will
499 * be allowed to start a shell or whatever an init script
502 dbg_message(L_LOG, "waiting for enter to start '%s'"
503 "(pid %d, tty '%s')\n",
504 a->command, getpid(), a->terminal);
505 full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1);
506 while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n')
511 * When a file named /.init_enable_core exists, setrlimit is called
512 * before processes are spawned to set core file size as unlimited.
513 * This is for debugging only. Don't use this is production, unless
514 * you want core dumps lying about....
516 if (ENABLE_FEATURE_INIT_COREDUMPS) {
517 if (access("/.init_enable_core", F_OK) == 0) {
519 limit.rlim_cur = RLIM_INFINITY;
520 limit.rlim_max = RLIM_INFINITY;
521 setrlimit(RLIMIT_CORE, &limit);
525 /* Log the process name and args */
526 message(L_LOG, "starting pid %d, tty '%s': '%s'",
527 getpid(), a->terminal, a->command);
529 /* Now run it. The new program will take over this PID,
530 * so nothing further in init.c should be run. */
531 init_exec(a->command);
532 /* We're still here? Some error happened. */
536 static struct init_action *mark_terminated(pid_t pid)
538 struct init_action *a;
541 update_utmp(pid, DEAD_PROCESS,
546 for (a = init_action_list; a; a = a->next) {
556 static void waitfor(pid_t pid)
558 /* waitfor(run(x)): protect against failed fork inside run() */
562 /* Wait for any child (prevent zombies from exiting orphaned processes)
563 * but exit the loop only when specified one has exited. */
565 pid_t wpid = wait(NULL);
566 mark_terminated(wpid);
567 /* Unsafe. SIGTSTP handler might have wait'ed it already */
568 /*if (wpid == pid) break;*/
575 /* Run all commands of a particular type */
576 static void run_actions(int action_type)
578 struct init_action *a;
580 for (a = init_action_list; a; a = a->next) {
581 if (!(a->action_type & action_type))
584 if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
586 if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
589 if (a->action_type & (RESPAWN | ASKFIRST)) {
590 /* Only run stuff with pid == 0. If pid != 0,
591 * it is already running
599 static void new_init_action(uint8_t action_type, const char *command, const char *cons)
601 struct init_action *a, **nextp;
605 * ::shutdown:umount -a -r
606 * ::shutdown:swapoff -a
608 * ::shutdown:swapoff -a
609 * ::shutdown:umount -a -r
610 * On reload, we must ensure entries end up in correct order.
611 * To achieve that, if we find a matching entry, we move it
614 nextp = &init_action_list;
615 while ((a = *nextp) != NULL) {
616 /* Don't enter action if it's already in the list.
617 * This prevents losing running RESPAWNs.
619 if (strcmp(a->command, command) == 0
620 && strcmp(a->terminal, cons) == 0
622 /* Remove from list */
624 /* Find the end of the list */
625 while (*nextp != NULL)
626 nextp = &(*nextp)->next;
633 a = xzalloc(sizeof(*a) + strlen(command));
635 /* Append to the end of the list */
638 a->action_type = action_type;
639 strcpy(a->command, command);
640 safe_strncpy(a->terminal, cons, sizeof(a->terminal));
641 dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%x tty='%s'\n",
642 a->command, a->action_type, a->terminal);
645 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
646 * then parse_inittab() simply adds in some default
647 * actions (i.e., runs INIT_SCRIPT and then starts a pair
648 * of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB
649 * _is_ defined, but /etc/inittab is missing, this
650 * results in the same set of default behaviors.
652 static void parse_inittab(void)
654 #if ENABLE_FEATURE_USE_INITTAB
656 parser_t *parser = config_open2("/etc/inittab", fopen_for_read);
661 /* No inittab file - set up some default behavior */
663 new_init_action(SYSINIT, INIT_SCRIPT, "");
664 /* Askfirst shell on tty1-4 */
665 new_init_action(ASKFIRST, bb_default_login_shell, "");
666 //TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
667 new_init_action(ASKFIRST, bb_default_login_shell, VC_2);
668 new_init_action(ASKFIRST, bb_default_login_shell, VC_3);
669 new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
670 /* Reboot on Ctrl-Alt-Del */
671 new_init_action(CTRLALTDEL, "reboot", "");
672 /* Umount all filesystems on halt/reboot */
673 new_init_action(SHUTDOWN, "umount -a -r", "");
674 /* Swapoff on halt/reboot */
675 new_init_action(SHUTDOWN, "swapoff -a", "");
676 /* Restart init when a QUIT is received */
677 new_init_action(RESTART, "init", "");
681 #if ENABLE_FEATURE_USE_INITTAB
682 /* optional_tty:ignored_runlevel:action:command
683 * Delims are not to be collapsed and need exactly 4 tokens
685 while (config_read(parser, token, 4, 0, "#:",
686 PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
687 /* order must correspond to SYSINIT..RESTART constants */
688 static const char actions[] ALIGN1 =
689 "sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
690 "ctrlaltdel\0""shutdown\0""restart\0";
692 char *tty = token[0];
694 if (!token[3]) /* less than 4 tokens */
696 action = index_in_strings(actions, token[2]);
697 if (action < 0 || !token[3][0]) /* token[3]: command */
699 /* turn .*TTY -> /dev/TTY */
701 tty = concat_path_file("/dev/", skip_dev_pfx(tty));
703 new_init_action(1 << action, token[3], tty);
708 message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d",
711 config_close(parser);
715 static void pause_and_low_level_reboot(unsigned magic) NORETURN;
716 static void pause_and_low_level_reboot(unsigned magic)
720 /* Allow time for last message to reach serial console, etc */
723 /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
724 * in linux/kernel/sys.c, which can cause the machine to panic when
725 * the init process exits... */
727 if (pid == 0) { /* child */
735 static void run_shutdown_and_kill_processes(void)
737 /* Run everything to be run at "shutdown". This is done _prior_
738 * to killing everything, in case people wish to use scripts to
739 * shut things down gracefully... */
740 run_actions(SHUTDOWN);
742 message(L_CONSOLE | L_LOG, "The system is going down NOW!");
744 /* Send signals to every process _except_ pid 1 */
746 message(L_CONSOLE | L_LOG, "Sent SIG%s to all processes", "TERM");
751 message(L_CONSOLE, "Sent SIG%s to all processes", "KILL");
753 /*sleep(1); - callers take care about making a pause */
756 /* Signal handling by init:
758 * For process with PID==1, on entry kernel sets all signals to SIG_DFL
759 * and unmasks all signals. However, for process with PID==1,
760 * default action (SIG_DFL) on any signal is to ignore it,
761 * even for special signals SIGKILL and SIGCONT.
762 * Also, any signal can be caught or blocked.
763 * (but SIGSTOP is still handled specially, at least in 2.6.20)
765 * We install two kinds of handlers, "immediate" and "delayed".
767 * Immediate handlers execute at any time, even while, say, sysinit
770 * Delayed handlers just set a flag variable. The variable is checked
771 * in the main loop and acted upon.
773 * halt/poweroff/reboot and restart have immediate handlers.
774 * They only traverse linked list of struct action's, never modify it,
775 * this should be safe to do even in signal handler. Also they
778 * SIGSTOP and SIGTSTP have immediate handlers. They just wait
779 * for SIGCONT to happen.
781 * SIGHUP has a delayed handler, because modifying linked list
782 * of struct action's from a signal handler while it is manipulated
783 * by the program may be disastrous.
785 * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
786 * it to happen even somewhere inside "sysinit" would be a bit awkward.
788 * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
789 * and only one will be remembered and acted upon.
792 /* The SIGPWR/SIGUSR[12]/SIGTERM handler */
793 static void halt_reboot_pwoff(int sig) NORETURN;
794 static void halt_reboot_pwoff(int sig)
799 /* We may call run() and it unmasks signals,
800 * including the one masked inside this signal handler.
801 * Testcase which would start multiple reboot scripts:
802 * while true; do reboot; done
805 reset_sighandlers_and_unblock_sigs();
807 run_shutdown_and_kill_processes();
811 if (sig == SIGTERM) {
814 } else if (sig == SIGUSR2) {
818 message(L_CONSOLE, "Requesting system %s", m);
819 pause_and_low_level_reboot(rb);
823 /* Handler for QUIT - exec "restart" action,
824 * else (no such action defined) do nothing */
825 static void restart_handler(int sig UNUSED_PARAM)
827 struct init_action *a;
829 for (a = init_action_list; a; a = a->next) {
830 if (!(a->action_type & RESTART))
833 /* Starting from here, we won't return.
834 * Thus don't need to worry about preserving errno
838 reset_sighandlers_and_unblock_sigs();
840 run_shutdown_and_kill_processes();
843 /* Allow Ctrl-Alt-Del to reboot the system.
844 * This is how kernel sets it up for init, we follow suit.
846 reboot(RB_ENABLE_CAD); /* misnomer */
849 if (open_stdio_to_tty(a->terminal)) {
850 dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
851 /* Theoretically should be safe.
852 * But in practice, kernel bugs may leave
853 * unkillable processes, and wait() may block forever.
854 * Oh well. Hoping "new" init won't be too surprised
855 * by having children it didn't create.
857 //while (wait(NULL) > 0)
859 init_exec(a->command);
861 /* Open or exec failed */
862 pause_and_low_level_reboot(RB_HALT_SYSTEM);
867 /* The SIGSTOP/SIGTSTP handler
868 * NB: inside it, all signals except SIGCONT are masked
869 * via appropriate setup in sigaction().
871 static void stop_handler(int sig UNUSED_PARAM)
873 smallint saved_bb_got_signal;
876 saved_bb_got_signal = bb_got_signal;
878 signal(SIGCONT, record_signo);
883 if (bb_got_signal == SIGCONT)
885 /* NB: this can accidentally wait() for a process
886 * which we waitfor() elsewhere! waitfor() must have
887 * code which is resilient against this.
889 wpid = wait_any_nohang(NULL);
890 mark_terminated(wpid);
894 signal(SIGCONT, SIG_DFL);
896 bb_got_signal = saved_bb_got_signal;
899 #if ENABLE_FEATURE_USE_INITTAB
900 static void reload_inittab(void)
902 struct init_action *a, **nextp;
904 message(L_LOG, "reloading /etc/inittab");
906 /* Disable old entries */
907 for (a = init_action_list; a; a = a->next)
910 /* Append new entries, or modify existing entries
911 * (incl. setting a->action_type) if cmd and device name
912 * match new ones. End result: only entries with
913 * a->action_type == 0 are stale.
917 #if ENABLE_FEATURE_KILL_REMOVED
918 /* Kill stale entries */
919 /* Be nice and send SIGTERM first */
920 for (a = init_action_list; a; a = a->next)
921 if (a->action_type == 0 && a->pid != 0)
922 kill(a->pid, SIGTERM);
923 if (CONFIG_FEATURE_KILL_DELAY) {
924 /* NB: parent will wait in NOMMU case */
925 if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
926 sleep(CONFIG_FEATURE_KILL_DELAY);
927 for (a = init_action_list; a; a = a->next)
928 if (a->action_type == 0 && a->pid != 0)
929 kill(a->pid, SIGKILL);
935 /* Remove stale entries and SYSINIT entries.
936 * We never rerun SYSINIT entries anyway,
937 * removing them too saves a few bytes
939 nextp = &init_action_list;
940 while ((a = *nextp) != NULL) {
942 * Why pid == 0 check?
943 * Process can be removed from inittab and added *later*.
944 * If we delete its entry but process still runs,
945 * duplicate is spawned when the entry is re-added.
947 if ((a->action_type & ~SYSINIT) == 0 && a->pid == 0) {
956 /* run_actions(RESPAWN | ASKFIRST); */
957 /* - we return to main loop, which does this automagically */
961 static int check_delayed_sigs(void)
966 smallint sig = bb_got_signal;
972 #if ENABLE_FEATURE_USE_INITTAB
977 run_actions(CTRLALTDEL);
981 #if DEBUG_SEGV_HANDLER
983 void handle_sigsegv(int sig, siginfo_t *info, void *ucontext)
989 ip = uc->uc_mcontext.gregs[REG_EIP];
990 fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n",
992 /* this is void*, but using %p would print "(null)"
993 * even for ptrs which are not exactly 0, but, say, 0x123:
998 /* glibc extension */
1001 size = backtrace(array, 50);
1002 backtrace_symbols_fd(array, size, 2);
1004 for (;;) sleep(9999);
1008 int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1009 int init_main(int argc UNUSED_PARAM, char **argv)
1011 if (argv[1] && strcmp(argv[1], "-q") == 0) {
1012 return kill(1, SIGHUP);
1015 #if DEBUG_SEGV_HANDLER
1017 struct sigaction sa;
1018 memset(&sa, 0, sizeof(sa));
1019 sa.sa_sigaction = handle_sigsegv;
1020 sa.sa_flags = SA_SIGINFO;
1021 sigaction(SIGSEGV, &sa, NULL);
1022 sigaction(SIGILL, &sa, NULL);
1023 sigaction(SIGFPE, &sa, NULL);
1024 sigaction(SIGBUS, &sa, NULL);
1029 /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
1031 && (!ENABLE_FEATURE_INITRD || applet_name[0] != 'l') /* not linuxrc? */
1033 bb_error_msg_and_die("must be run as PID 1");
1035 #ifdef RB_DISABLE_CAD
1036 /* Turn off rebooting via CTL-ALT-DEL - we get a
1037 * SIGINT on CAD so we can shut things down gracefully... */
1038 reboot(RB_DISABLE_CAD); /* misnomer */
1042 /* If, say, xmalloc would ever die, we don't want to oops kernel
1044 * NB: we set die_sleep *after* PID 1 check and bb_show_usage.
1045 * Otherwise, for example, "init u" ("please rexec yourself"
1046 * command for sysvinit) will show help text (which isn't too bad),
1047 * *and sleep forever* (which is bad!)
1049 die_sleep = 30 * 24*60*60;
1051 /* Figure out where the default console should be */
1057 /* Make sure environs is set to something sane */
1058 putenv((char *) "HOME=/");
1059 putenv((char *) bb_PATH_root_path);
1060 putenv((char *) "SHELL=/bin/sh");
1061 putenv((char *) "USER=root"); /* needed? why? */
1064 xsetenv("RUNLEVEL", argv[1]);
1066 #if !ENABLE_FEATURE_EXTRA_QUIET
1068 message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
1072 /* It's 2013, does anyone really still depend on this? */
1073 /* If you do, consider adding swapon to sysinot actions then! */
1074 /* struct sysinfo is linux-specific */
1076 /* Make sure there is enough memory to do something useful. */
1077 /*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ {
1078 struct sysinfo info;
1080 if (sysinfo(&info) == 0
1081 && (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024
1083 message(L_CONSOLE, "Low memory, forcing swapon");
1084 /* swapon -a requires /proc typically */
1085 new_init_action(SYSINIT, "mount -t proc proc /proc", "");
1086 /* Try to turn on swap */
1087 new_init_action(SYSINIT, "swapon -a", "");
1088 run_actions(SYSINIT); /* wait and removing */
1094 /* Check if we are supposed to be in single user mode */
1096 && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
1098 /* ??? shouldn't we set RUNLEVEL="b" here? */
1099 /* Start a shell on console */
1100 new_init_action(RESPAWN, bb_default_login_shell, "");
1102 /* Not in single user mode - see what inittab says */
1104 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
1105 * then parse_inittab() simply adds in some default
1106 * actions (i.e., INIT_SCRIPT and a pair
1107 * of "askfirst" shells) */
1112 if (getenv("SELINUX_INIT") == NULL) {
1115 putenv((char*)"SELINUX_INIT=YES");
1116 if (selinux_init_load_policy(&enforce) == 0) {
1117 BB_EXECVP(argv[0], argv);
1118 } else if (enforce > 0) {
1119 /* SELinux in enforcing mode but load_policy failed */
1120 message(L_CONSOLE, "can't load SELinux Policy. "
1121 "Machine is in enforcing mode. Halting now.");
1122 return EXIT_FAILURE;
1127 /* Make the command line just say "init" - thats all, nothing else */
1128 strncpy(argv[0], "init", strlen(argv[0]));
1129 /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
1133 /* Set up signal handlers */
1135 struct sigaction sa;
1138 + (1 << SIGPWR) /* halt */
1139 + (1 << SIGUSR1) /* halt */
1140 + (1 << SIGTERM) /* reboot */
1141 + (1 << SIGUSR2) /* poweroff */
1142 , halt_reboot_pwoff);
1143 signal(SIGQUIT, restart_handler); /* re-exec another init */
1145 /* Stop handler must allow only SIGCONT inside itself */
1146 memset(&sa, 0, sizeof(sa));
1147 sigfillset(&sa.sa_mask);
1148 sigdelset(&sa.sa_mask, SIGCONT);
1149 sa.sa_handler = stop_handler;
1150 /* NB: sa_flags doesn't have SA_RESTART.
1151 * It must be able to interrupt wait().
1153 sigaction_set(SIGTSTP, &sa); /* pause */
1154 /* Does not work as intended, at least in 2.6.20.
1155 * SIGSTOP is simply ignored by init:
1157 sigaction_set(SIGSTOP, &sa); /* pause */
1159 /* SIGINT (Ctrl-Alt-Del) must interrupt wait(),
1160 * setting handler without SA_RESTART flag.
1162 bb_signals_recursive_norestart((1 << SIGINT), record_signo);
1165 /* Set up "reread /etc/inittab" handler.
1166 * Handler is set up without SA_RESTART, it will interrupt syscalls.
1168 if (!DEBUG_INIT && ENABLE_FEATURE_USE_INITTAB)
1169 bb_signals_recursive_norestart((1 << SIGHUP), record_signo);
1171 /* Now run everything that needs to be run */
1172 /* First run the sysinit command */
1173 run_actions(SYSINIT);
1174 check_delayed_sigs();
1175 /* Next run anything that wants to block */
1177 check_delayed_sigs();
1178 /* Next run anything to be run only once */
1181 /* Now run the looping stuff for the rest of forever.
1186 maybe_WNOHANG = check_delayed_sigs();
1188 /* (Re)run the respawn/askfirst stuff */
1189 run_actions(RESPAWN | ASKFIRST);
1190 maybe_WNOHANG |= check_delayed_sigs();
1192 /* Don't consume all CPU time - sleep a bit */
1194 maybe_WNOHANG |= check_delayed_sigs();
1196 /* Wait for any child process(es) to exit.
1198 * If check_delayed_sigs above reported that a signal
1199 * was caught, wait will be nonblocking. This ensures
1200 * that if SIGHUP has reloaded inittab, respawn and askfirst
1201 * actions will not be delayed until next child death.
1204 maybe_WNOHANG = WNOHANG;
1207 struct init_action *a;
1209 /* If signals happen _in_ the wait, they interrupt it,
1210 * bb_signals_recursive_norestart set them up that way
1212 wpid = waitpid(-1, NULL, maybe_WNOHANG);
1216 a = mark_terminated(wpid);
1218 message(L_LOG, "process '%s' (pid %d) exited. "
1219 "Scheduling for restart.",
1222 /* See if anyone else is waiting to be reaped */
1223 maybe_WNOHANG = WNOHANG;
1228 //usage:#define linuxrc_trivial_usage NOUSAGE_STR
1229 //usage:#define linuxrc_full_usage ""
1231 //usage:#define init_trivial_usage
1233 //usage:#define init_full_usage "\n\n"
1234 //usage: "Init is the first process started during boot. It never exits."
1235 //usage: IF_FEATURE_USE_INITTAB(
1236 //usage: "\n""It (re)spawns children according to /etc/inittab."
1238 //usage: IF_NOT_FEATURE_USE_INITTAB(
1239 //usage: "\n""This version of init doesn't use /etc/inittab,"
1240 //usage: "\n""has fixed set of processed to run."
1243 //usage:#define init_notes_usage
1244 //usage: "This version of init is designed to be run only by the kernel.\n"
1246 //usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
1247 //usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
1248 //usage: "runlevels, use sysvinit.\n"
1250 //usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n"
1251 //usage: "it has the following default behavior:\n"
1253 //usage: " ::sysinit:/etc/init.d/rcS\n"
1254 //usage: " ::askfirst:/bin/sh\n"
1255 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1256 //usage: " ::shutdown:/sbin/swapoff -a\n"
1257 //usage: " ::shutdown:/bin/umount -a -r\n"
1258 //usage: " ::restart:/sbin/init\n"
1259 //usage: " tty2::askfirst:/bin/sh\n"
1260 //usage: " tty3::askfirst:/bin/sh\n"
1261 //usage: " tty4::askfirst:/bin/sh\n"
1263 //usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
1265 //usage: " <id>:<runlevels>:<action>:<process>\n"
1269 //usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n"
1270 //usage: " The id field is used by BusyBox init to specify the controlling tty for\n"
1271 //usage: " the specified process to run on. The contents of this field are\n"
1272 //usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n"
1273 //usage: " be unique, although if it isn't you may have strange results. If this\n"
1274 //usage: " field is left blank, then the init's stdin/out will be used.\n"
1276 //usage: " <runlevels>:\n"
1278 //usage: " The runlevels field is completely ignored.\n"
1280 //usage: " <action>:\n"
1282 //usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n"
1283 //usage: " once, restart, ctrlaltdel, and shutdown.\n"
1285 //usage: " The available actions can be classified into two groups: actions\n"
1286 //usage: " that are run only once, and actions that are re-run when the specified\n"
1287 //usage: " process exits.\n"
1289 //usage: " Run only-once actions:\n"
1291 //usage: " 'sysinit' is the first item run on boot. init waits until all\n"
1292 //usage: " sysinit actions are completed before continuing. Following the\n"
1293 //usage: " completion of all sysinit actions, all 'wait' actions are run.\n"
1294 //usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n"
1295 //usage: " the specified task completes. 'once' actions are asynchronous,\n"
1296 //usage: " therefore, init does not wait for them to complete. 'restart' is\n"
1297 //usage: " the action taken to restart the init process. By default this should\n"
1298 //usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n"
1299 //usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
1300 //usage: " actions are run when the system detects that someone on the system\n"
1301 //usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
1302 //usage: " wants to run 'reboot' at this point to cause the system to reboot.\n"
1303 //usage: " Finally the 'shutdown' action specifies the actions to taken when\n"
1304 //usage: " init is told to reboot. Unmounting filesystems and disabling swap\n"
1305 //usage: " is a very good here.\n"
1307 //usage: " Run repeatedly actions:\n"
1309 //usage: " 'respawn' actions are run after the 'once' actions. When a process\n"
1310 //usage: " started with a 'respawn' action exits, init automatically restarts\n"
1311 //usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n"
1312 //usage: " respawning out of control. The 'askfirst' actions acts just like\n"
1313 //usage: " respawn, except that before running the specified process it\n"
1314 //usage: " displays the line \"Please press Enter to activate this console.\"\n"
1315 //usage: " and then waits for the user to press enter before starting the\n"
1316 //usage: " specified process.\n"
1318 //usage: " Unrecognized actions (like initdefault) will cause init to emit an\n"
1319 //usage: " error message, and then go along with its business. All actions are\n"
1320 //usage: " run in the order they appear in /etc/inittab.\n"
1322 //usage: " <process>:\n"
1324 //usage: " Specifies the process to be executed and its command line.\n"
1326 //usage: "Example /etc/inittab file:\n"
1328 //usage: " # This is run first except when booting in single-user mode\n"
1330 //usage: " ::sysinit:/etc/init.d/rcS\n"
1332 //usage: " # /bin/sh invocations on selected ttys\n"
1334 //usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n"
1335 //usage: " ::askfirst:-/bin/sh\n"
1336 //usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n"
1337 //usage: " tty2::askfirst:-/bin/sh\n"
1338 //usage: " tty3::askfirst:-/bin/sh\n"
1339 //usage: " tty4::askfirst:-/bin/sh\n"
1341 //usage: " # /sbin/getty invocations for selected ttys\n"
1343 //usage: " tty4::respawn:/sbin/getty 38400 tty4\n"
1344 //usage: " tty5::respawn:/sbin/getty 38400 tty5\n"
1347 //usage: " # Example of how to put a getty on a serial line (for a terminal)\n"
1349 //usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
1350 //usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
1352 //usage: " # Example how to put a getty on a modem line\n"
1353 //usage: " #::respawn:/sbin/getty 57600 ttyS2\n"
1355 //usage: " # Stuff to do when restarting the init process\n"
1356 //usage: " ::restart:/sbin/init\n"
1358 //usage: " # Stuff to do before rebooting\n"
1359 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1360 //usage: " ::shutdown:/bin/umount -a -r\n"
1361 //usage: " ::shutdown:/sbin/swapoff -a\n"