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.
12 //config: bool "init (9.3 kb)"
14 //config: select FEATURE_SYSLOG
16 //config: init is the first program run when the system boots.
18 //config:config LINUXRC
19 //config: bool "linuxrc: support running init from initrd (not initramfs)"
21 //config: select FEATURE_SYSLOG
23 //config: Legacy support for running init under the old-style initrd. Allows
24 //config: the name linuxrc to act as init, and it doesn't assume init is PID 1.
26 //config: This does not apply to initramfs, which runs /init as PID 1 and
27 //config: requires no special support.
29 //config:config FEATURE_USE_INITTAB
30 //config: bool "Support reading an inittab file"
32 //config: depends on INIT || LINUXRC
34 //config: Allow init to read an inittab file when the system boot.
36 //config:config FEATURE_KILL_REMOVED
37 //config: bool "Support killing processes that have been removed from inittab"
39 //config: depends on FEATURE_USE_INITTAB
41 //config: When respawn entries are removed from inittab and a SIGHUP is
42 //config: sent to init, this option will make init kill the processes
43 //config: that have been removed.
45 //config:config FEATURE_KILL_DELAY
46 //config: int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED
47 //config: range 0 1024
49 //config: depends on FEATURE_KILL_REMOVED
51 //config: With nonzero setting, init sends TERM, forks, child waits N
52 //config: seconds, sends KILL and exits. Setting it too high is unwise
53 //config: (child will hang around for too long and could actually kill
54 //config: the wrong process!)
56 //config:config FEATURE_INIT_SCTTY
57 //config: bool "Run commands with leading dash with controlling tty"
59 //config: depends on INIT || LINUXRC
61 //config: If this option is enabled, init will try to give a controlling
62 //config: tty to any command which has leading hyphen (often it's "-/bin/sh").
63 //config: More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)".
64 //config: If device attached to STDIN_FILENO can be a ctty but is not yet
65 //config: a ctty for other session, it will become this process' ctty.
66 //config: This is not the traditional init behavour, but is often what you want
67 //config: in an embedded system where the console is only accessed during
68 //config: development or for maintenance.
69 //config: NB: using cttyhack applet may work better.
71 //config:config FEATURE_INIT_SYSLOG
72 //config: bool "Enable init to write to syslog"
74 //config: depends on INIT || LINUXRC
76 //config: If selected, some init messages are sent to syslog.
77 //config: Otherwise, they are sent to VT #5 if linux virtual tty is detected
78 //config: (if not, no separate logging is done).
80 //config:config FEATURE_INIT_QUIET
81 //config: bool "Be quiet on boot (no 'init started:' message)"
83 //config: depends on INIT || LINUXRC
85 //config:config FEATURE_INIT_COREDUMPS
86 //config: bool "Support dumping core for child processes (debugging only)"
87 //config: default n # not Y because this is a debug option
88 //config: depends on INIT || LINUXRC
90 //config: If this option is enabled and the file /.init_enable_core
91 //config: exists, then init will call setrlimit() to allow unlimited
92 //config: core file sizes. If this option is disabled, processes
93 //config: will not generate any core files.
95 //config:config INIT_TERMINAL_TYPE
96 //config: string "Initial terminal type"
97 //config: default "linux"
98 //config: depends on INIT || LINUXRC
100 //config: This is the initial value set by init for the TERM environment
101 //config: variable. This variable is used by programs which make use of
102 //config: extended terminal capabilities.
104 //config: Note that on Linux, init attempts to detect serial terminal and
105 //config: sets TERM to "vt102" if one is found.
107 //config:config FEATURE_INIT_MODIFY_CMDLINE
108 //config: bool "Clear init's command line"
110 //config: depends on INIT || LINUXRC
112 //config: When launched as PID 1 and after parsing its arguments, init
113 //config: wipes all the arguments but argv[0] and rewrites argv[0] to
114 //config: contain only "init", so that its command line appears solely as
115 //config: "init" in tools such as ps.
116 //config: If this option is set to Y, init will keep its original behavior,
117 //config: otherwise, all the arguments including argv[0] will be preserved,
118 //config: be they parsed or ignored by init.
119 //config: The original command-line used to launch init can then be
120 //config: retrieved in /proc/1/cmdline on Linux, for example.
122 //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
123 //applet:IF_LINUXRC(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
125 //kbuild:lib-$(CONFIG_INIT) += init.o
126 //kbuild:lib-$(CONFIG_LINUXRC) += init.o
128 #define DEBUG_SEGV_HANDLER 0
132 #include <sys/resource.h>
134 # include <linux/vt.h>
135 # include <sys/sysinfo.h>
137 #include "reboot.h" /* reboot() constants */
139 #if DEBUG_SEGV_HANDLER
141 # define _GNU_SOURCE 1
144 # include <execinfo.h>
145 # include <sys/ucontext.h>
148 /* Used only for sanitizing purposes in set_sane_term() below. On systems where
149 * the baud rate is stored in a separate field, we can safely disable them. */
155 /* Was a CONFIG_xxx option. A lot of people were building
156 * not fully functional init by switching it on! */
159 #define CONSOLE_NAME_SIZE 32
161 /* Default sysinit script. */
163 # define INIT_SCRIPT "/etc/init.d/rcS"
166 /* Each type of actions can appear many times. They will be
167 * handled in order. RESTART is an exception, only 1st is used.
169 /* Start these actions first and wait for completion */
171 /* Start these after SYSINIT and wait for completion */
173 /* Start these after WAIT and *dont* wait for completion */
176 * NB: while SYSINIT/WAIT/ONCE are being processed,
177 * SIGHUP ("reread /etc/inittab") will be processed only after
178 * each group of actions. If new inittab adds, say, a SYSINIT action,
179 * it will not be run, since init is already "past SYSINIT stage".
181 /* Start these after ONCE are started, restart on exit */
183 /* Like RESPAWN, but wait for <Enter> to be pressed on tty */
184 #define ASKFIRST 0x10
186 * Start these on SIGINT, and wait for completion.
187 * Then go back to respawning RESPAWN and ASKFIRST actions.
188 * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
190 #define CTRLALTDEL 0x20
192 * Start these before killing all processes in preparation for
193 * running RESTART actions or doing low-level halt/reboot/poweroff
194 * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
195 * Wait for completion before proceeding.
197 #define SHUTDOWN 0x40
199 * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
200 * then all processes are killed, then init exec's 1st RESTART action,
201 * replacing itself by it. If no RESTART action specified,
202 * SIGQUIT has no effect.
207 /* A linked list of init_actions, to be read from inittab */
209 struct init_action *next;
212 char terminal[CONSOLE_NAME_SIZE];
216 static struct init_action *init_action_list = NULL;
218 #if !ENABLE_FEATURE_INIT_SYSLOG
219 static const char *log_console = VC_5;
227 /* Print a message to the specified device.
228 * "where" may be bitwise-or'd from L_LOG | L_CONSOLE
229 * NB: careful, we can be called after vfork!
231 #define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
232 static void message(int where, const char *fmt, ...)
233 __attribute__ ((format(printf, 2, 3)));
234 static void message(int where, const char *fmt, ...)
241 va_start(arguments, fmt);
242 l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments);
243 if (l > sizeof(msg) - 2)
247 #if ENABLE_FEATURE_INIT_SYSLOG
250 /* Log the message to syslogd */
251 openlog(applet_name, 0, LOG_DAEMON);
252 /* don't print "\r" */
253 syslog(LOG_INFO, "%s", msg + 1);
262 /* Take full control of the log tty, and never close it.
263 * It's mine, all mine! Muhahahaha! */
264 static int log_fd = -1;
267 log_fd = STDERR_FILENO;
269 log_fd = device_open(log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY);
271 bb_error_msg("can't log to %s", log_console);
274 close_on_exec_on(log_fd);
278 full_write(log_fd, msg, l);
279 if (log_fd == STDERR_FILENO)
280 return; /* don't print dup messages */
284 if (where & L_CONSOLE) {
285 /* Send console messages to console so people will see them. */
286 full_write(STDERR_FILENO, msg, l);
290 static void console_init(void)
297 s = getenv("CONSOLE");
299 s = getenv("console");
300 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
301 /* BSD people say their kernels do not open fd 0,1,2; they need this: */
303 s = (char*)"/dev/console";
306 int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY);
308 dup2(fd, STDIN_FILENO);
309 dup2(fd, STDOUT_FILENO);
310 xmove_fd(fd, STDERR_FILENO);
312 dbg_message(L_LOG, "console='%s'", s);
314 /* Make sure fd 0,1,2 are not closed
315 * (so that they won't be used by future opens) */
317 // Users report problems
318 // /* Make sure init can't be blocked by writing to stderr */
319 // fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK);
324 if (ioctl(STDIN_FILENO, VT_OPENQRY, &vtno) != 0) {
325 /* Not a linux terminal, probably serial console.
326 * Force the TERM setting to vt102
327 * if TERM is set to linux (the default) */
328 if (!s || strcmp(s, "linux") == 0)
329 putenv((char*)"TERM=vt102");
330 # if !ENABLE_FEATURE_INIT_SYSLOG
336 putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE);
339 /* Set terminal settings to reasonable defaults.
340 * NB: careful, we can be called after vfork! */
341 static void set_sane_term(void)
345 tcgetattr(STDIN_FILENO, &tty);
347 /* set control chars */
348 tty.c_cc[VINTR] = 3; /* C-c */
349 tty.c_cc[VQUIT] = 28; /* C-\ */
350 tty.c_cc[VERASE] = 127; /* C-? */
351 tty.c_cc[VKILL] = 21; /* C-u */
352 tty.c_cc[VEOF] = 4; /* C-d */
353 tty.c_cc[VSTART] = 17; /* C-q */
354 tty.c_cc[VSTOP] = 19; /* C-s */
355 tty.c_cc[VSUSP] = 26; /* C-z */
358 /* use line discipline 0 */
362 /* Make it be sane */
366 /* added CRTSCTS to fix Debian bug 528560 */
367 tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS;
368 tty.c_cflag |= CREAD | HUPCL | CLOCAL;
371 tty.c_iflag = ICRNL | IXON | IXOFF;
374 tty.c_oflag = OPOST | ONLCR;
377 tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN;
379 tcsetattr_stdin_TCSANOW(&tty);
382 /* Open the new terminal device.
383 * NB: careful, we can be called after vfork! */
384 static int open_stdio_to_tty(const char* tty_name)
386 /* empty tty_name means "use init's tty", else... */
391 /* fd can be only < 0 or 0: */
392 fd = device_open(tty_name, O_RDWR);
394 message(L_LOG | L_CONSOLE, "can't open %s: %s",
395 tty_name, strerror(errno));
396 return 0; /* failure */
398 dup2(STDIN_FILENO, STDOUT_FILENO);
399 dup2(STDIN_FILENO, STDERR_FILENO);
402 return 1; /* success */
405 static void reset_sighandlers_and_unblock_sigs(void)
417 sigprocmask_allsigs(SIG_UNBLOCK);
420 /* Wrapper around exec:
422 * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
423 * Otherwise splits words on whitespace, deals with leading dash,
424 * and uses plain exec().
425 * NB: careful, we can be called after vfork!
427 static void init_exec(const char *command)
429 /* +8 allows to write VLA sizes below more efficiently: */
430 unsigned command_size = strlen(command) + 8;
431 /* strlen(command) + strlen("exec ")+1: */
432 char buf[command_size];
433 /* strlen(command) / 2 + 4: */
434 char *cmd[command_size / 2];
437 dash = (command[0] == '-' /* maybe? && command[1] == '/' */);
440 /* See if any special /bin/sh requiring characters are present */
441 if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
442 sprintf(buf, "exec %s", command); /* excluding "-" */
443 /* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
444 cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash);
445 cmd[1] = (char*)"-c";
448 command = LIBBB_DEFAULT_LOGIN_SHELL + 1;
450 /* Convert command (char*) into cmd (char**, one word per string) */
453 next = strcpy(buf, command - dash); /* command including "-" */
454 command = next + dash;
455 while ((word = strsep(&next, " \t")) != NULL) {
456 if (*word != '\0') { /* not two spaces/tabs together? */
463 /* If we saw leading "-", it is interactive shell.
464 * Try harder to give it a controlling tty.
466 if (ENABLE_FEATURE_INIT_SCTTY && dash) {
467 /* _Attempt_ to make stdin a controlling tty. */
468 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/);
470 /* Here command never contains the dash, cmd[0] might */
471 BB_EXECVP(command, cmd);
472 message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno));
473 /* returns if execvp fails */
476 /* Used only by run_actions */
477 static pid_t run(const struct init_action *a)
481 /* Careful: don't be affected by a signal in vforked child */
482 sigprocmask_allsigs(SIG_BLOCK);
483 if (BB_MMU && (a->action_type & ASKFIRST))
488 message(L_LOG | L_CONSOLE, "can't fork");
490 sigprocmask_allsigs(SIG_UNBLOCK);
491 return pid; /* Parent or error */
496 /* Reset signal handlers that were set by the parent process */
497 reset_sighandlers_and_unblock_sigs();
499 /* Create a new session and make ourself the process group leader */
502 /* Open the new terminal device */
503 if (!open_stdio_to_tty(a->terminal))
506 /* NB: on NOMMU we can't wait for input in child, so
507 * "askfirst" will work the same as "respawn". */
508 if (BB_MMU && (a->action_type & ASKFIRST)) {
509 static const char press_enter[] ALIGN1 =
510 #ifdef CUSTOMIZED_BANNER
511 #include CUSTOMIZED_BANNER
513 "\nPlease press Enter to activate this console. ";
516 * Save memory by not exec-ing anything large (like a shell)
517 * before the user wants it. This is critical if swap is not
518 * enabled and the system has low memory. Generally this will
519 * be run on the second virtual console, and the first will
520 * be allowed to start a shell or whatever an init script
523 dbg_message(L_LOG, "waiting for enter to start '%s'"
524 "(pid %d, tty '%s')\n",
525 a->command, getpid(), a->terminal);
526 full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1);
527 while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n')
532 * When a file named /.init_enable_core exists, setrlimit is called
533 * before processes are spawned to set core file size as unlimited.
534 * This is for debugging only. Don't use this is production, unless
535 * you want core dumps lying about....
537 if (ENABLE_FEATURE_INIT_COREDUMPS) {
538 if (access("/.init_enable_core", F_OK) == 0) {
540 limit.rlim_cur = RLIM_INFINITY;
541 limit.rlim_max = RLIM_INFINITY;
542 setrlimit(RLIMIT_CORE, &limit);
546 /* Log the process name and args */
547 message(L_LOG, "starting pid %u, tty '%s': '%s'",
548 (int)getpid(), a->terminal, a->command);
550 /* Now run it. The new program will take over this PID,
551 * so nothing further in init.c should be run. */
552 init_exec(a->command);
553 /* We're still here? Some error happened. */
557 static struct init_action *mark_terminated(pid_t pid)
559 struct init_action *a;
562 update_utmp_DEAD_PROCESS(pid);
563 for (a = init_action_list; a; a = a->next) {
573 static void waitfor(pid_t pid)
575 /* waitfor(run(x)): protect against failed fork inside run() */
579 /* Wait for any child (prevent zombies from exiting orphaned processes)
580 * but exit the loop only when specified one has exited. */
582 pid_t wpid = wait(NULL);
583 mark_terminated(wpid);
584 /* Unsafe. SIGTSTP handler might have wait'ed it already */
585 /*if (wpid == pid) break;*/
592 /* Run all commands of a particular type */
593 static void run_actions(int action_type)
595 struct init_action *a;
597 for (a = init_action_list; a; a = a->next) {
598 if (!(a->action_type & action_type))
601 if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
603 if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
606 if (a->action_type & (RESPAWN | ASKFIRST)) {
607 /* Only run stuff with pid == 0. If pid != 0,
608 * it is already running
616 static void new_init_action(uint8_t action_type, const char *command, const char *cons)
618 struct init_action *a, **nextp;
622 * ::shutdown:umount -a -r
623 * ::shutdown:swapoff -a
625 * ::shutdown:swapoff -a
626 * ::shutdown:umount -a -r
627 * On reload, we must ensure entries end up in correct order.
628 * To achieve that, if we find a matching entry, we move it
631 nextp = &init_action_list;
632 while ((a = *nextp) != NULL) {
633 /* Don't enter action if it's already in the list.
634 * This prevents losing running RESPAWNs.
636 if (strcmp(a->command, command) == 0
637 && strcmp(a->terminal, cons) == 0
639 /* Remove from list */
641 /* Find the end of the list */
642 while (*nextp != NULL)
643 nextp = &(*nextp)->next;
650 a = xzalloc(sizeof(*a) + strlen(command));
652 /* Append to the end of the list */
655 a->action_type = action_type;
656 strcpy(a->command, command);
657 safe_strncpy(a->terminal, cons, sizeof(a->terminal));
658 dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%x tty='%s'\n",
659 a->command, a->action_type, a->terminal);
662 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
663 * then parse_inittab() simply adds in some default
664 * actions (i.e., runs INIT_SCRIPT and then starts a pair
665 * of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB
666 * _is_ defined, but /etc/inittab is missing, this
667 * results in the same set of default behaviors.
669 static void parse_inittab(void)
671 #if ENABLE_FEATURE_USE_INITTAB
673 parser_t *parser = config_open2("/etc/inittab", fopen_for_read);
678 /* No inittab file - set up some default behavior */
680 new_init_action(SYSINIT, INIT_SCRIPT, "");
681 /* Askfirst shell on tty1-4 */
682 new_init_action(ASKFIRST, bb_default_login_shell, "");
683 //TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
684 new_init_action(ASKFIRST, bb_default_login_shell, VC_2);
685 new_init_action(ASKFIRST, bb_default_login_shell, VC_3);
686 new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
687 /* Reboot on Ctrl-Alt-Del */
688 new_init_action(CTRLALTDEL, "reboot", "");
689 /* Umount all filesystems on halt/reboot */
690 new_init_action(SHUTDOWN, "umount -a -r", "");
691 /* Swapoff on halt/reboot */
692 new_init_action(SHUTDOWN, "swapoff -a", "");
693 /* Restart init when a QUIT is received */
694 new_init_action(RESTART, "init", "");
698 #if ENABLE_FEATURE_USE_INITTAB
699 /* optional_tty:ignored_runlevel:action:command
700 * Delims are not to be collapsed and need exactly 4 tokens
702 while (config_read(parser, token, 4, 0, "#:",
703 PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
704 /* order must correspond to SYSINIT..RESTART constants */
705 static const char actions[] ALIGN1 =
706 "sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
707 "ctrlaltdel\0""shutdown\0""restart\0";
709 char *tty = token[0];
711 if (!token[3]) /* less than 4 tokens */
713 action = index_in_strings(actions, token[2]);
714 if (action < 0 || !token[3][0]) /* token[3]: command */
716 /* turn .*TTY -> /dev/TTY */
718 tty = concat_path_file("/dev/", skip_dev_pfx(tty));
720 new_init_action(1 << action, token[3], tty);
725 message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d",
728 config_close(parser);
732 static void pause_and_low_level_reboot(unsigned magic) NORETURN;
733 static void pause_and_low_level_reboot(unsigned magic)
737 /* Allow time for last message to reach serial console, etc */
740 /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
741 * in linux/kernel/sys.c, which can cause the machine to panic when
742 * the init process exits... */
744 if (pid == 0) { /* child */
752 static void run_shutdown_and_kill_processes(void)
754 /* Run everything to be run at "shutdown". This is done _prior_
755 * to killing everything, in case people wish to use scripts to
756 * shut things down gracefully... */
757 run_actions(SHUTDOWN);
759 message(L_CONSOLE | L_LOG, "The system is going down NOW!");
761 /* Send signals to every process _except_ pid 1 */
763 message(L_CONSOLE, "Sent SIG%s to all processes", "TERM");
768 message(L_CONSOLE, "Sent SIG%s to all processes", "KILL");
770 /*sleep(1); - callers take care about making a pause */
773 /* Signal handling by init:
775 * For process with PID==1, on entry kernel sets all signals to SIG_DFL
776 * and unmasks all signals. However, for process with PID==1,
777 * default action (SIG_DFL) on any signal is to ignore it,
778 * even for special signals SIGKILL and SIGCONT.
779 * Also, any signal can be caught or blocked.
780 * (but SIGSTOP is still handled specially, at least in 2.6.20)
782 * We install two kinds of handlers, "immediate" and "delayed".
784 * Immediate handlers execute at any time, even while, say, sysinit
787 * Delayed handlers just set a flag variable. The variable is checked
788 * in the main loop and acted upon.
790 * halt/poweroff/reboot and restart have immediate handlers.
791 * They only traverse linked list of struct action's, never modify it,
792 * this should be safe to do even in signal handler. Also they
795 * SIGSTOP and SIGTSTP have immediate handlers. They just wait
796 * for SIGCONT to happen.
798 * SIGHUP has a delayed handler, because modifying linked list
799 * of struct action's from a signal handler while it is manipulated
800 * by the program may be disastrous.
802 * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
803 * it to happen even somewhere inside "sysinit" would be a bit awkward.
805 * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
806 * and only one will be remembered and acted upon.
809 /* The SIGPWR/SIGUSR[12]/SIGTERM handler */
810 static void halt_reboot_pwoff(int sig) NORETURN;
811 static void halt_reboot_pwoff(int sig)
816 /* We may call run() and it unmasks signals,
817 * including the one masked inside this signal handler.
818 * Testcase which would start multiple reboot scripts:
819 * while true; do reboot; done
822 reset_sighandlers_and_unblock_sigs();
824 run_shutdown_and_kill_processes();
828 if (sig == SIGTERM) {
831 } else if (sig == SIGUSR2) {
835 message(L_CONSOLE, "Requesting system %s", m);
836 pause_and_low_level_reboot(rb);
840 /* Handler for QUIT - exec "restart" action,
841 * else (no such action defined) do nothing */
842 static void exec_restart_action(void)
844 struct init_action *a;
846 for (a = init_action_list; a; a = a->next) {
847 if (!(a->action_type & RESTART))
850 /* Starting from here, we won't return.
851 * Thus don't need to worry about preserving errno
855 reset_sighandlers_and_unblock_sigs();
857 run_shutdown_and_kill_processes();
860 /* Allow Ctrl-Alt-Del to reboot the system.
861 * This is how kernel sets it up for init, we follow suit.
863 reboot(RB_ENABLE_CAD); /* misnomer */
866 if (open_stdio_to_tty(a->terminal)) {
867 dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
868 /* Theoretically should be safe.
869 * But in practice, kernel bugs may leave
870 * unkillable processes, and wait() may block forever.
871 * Oh well. Hoping "new" init won't be too surprised
872 * by having children it didn't create.
874 //while (wait(NULL) > 0)
876 init_exec(a->command);
878 /* Open or exec failed */
879 pause_and_low_level_reboot(RB_HALT_SYSTEM);
884 /* The SIGSTOP/SIGTSTP handler
885 * NB: inside it, all signals except SIGCONT are masked
886 * via appropriate setup in sigaction().
888 static void stop_handler(int sig UNUSED_PARAM)
890 smallint saved_bb_got_signal;
893 saved_bb_got_signal = bb_got_signal;
895 signal(SIGCONT, record_signo);
900 if (bb_got_signal == SIGCONT)
902 /* NB: this can accidentally wait() for a process
903 * which we waitfor() elsewhere! waitfor() must have
904 * code which is resilient against this.
906 wpid = wait_any_nohang(NULL);
907 mark_terminated(wpid);
911 signal(SIGCONT, SIG_DFL);
913 bb_got_signal = saved_bb_got_signal;
916 #if ENABLE_FEATURE_USE_INITTAB
917 static void reload_inittab(void)
919 struct init_action *a, **nextp;
921 message(L_LOG, "reloading /etc/inittab");
923 /* Disable old entries */
924 for (a = init_action_list; a; a = a->next)
927 /* Append new entries, or modify existing entries
928 * (incl. setting a->action_type) if cmd and device name
929 * match new ones. End result: only entries with
930 * a->action_type == 0 are stale.
934 #if ENABLE_FEATURE_KILL_REMOVED
935 /* Kill stale entries */
936 /* Be nice and send SIGTERM first */
937 for (a = init_action_list; a; a = a->next)
938 if (a->action_type == 0 && a->pid != 0)
939 kill(a->pid, SIGTERM);
940 if (CONFIG_FEATURE_KILL_DELAY) {
941 /* NB: parent will wait in NOMMU case */
942 if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
943 sleep(CONFIG_FEATURE_KILL_DELAY);
944 for (a = init_action_list; a; a = a->next)
945 if (a->action_type == 0 && a->pid != 0)
946 kill(a->pid, SIGKILL);
952 /* Remove stale entries and SYSINIT entries.
953 * We never rerun SYSINIT entries anyway,
954 * removing them too saves a few bytes
956 nextp = &init_action_list;
957 while ((a = *nextp) != NULL) {
959 * Why pid == 0 check?
960 * Process can be removed from inittab and added *later*.
961 * If we delete its entry but process still runs,
962 * duplicate is spawned when the entry is re-added.
964 if ((a->action_type & ~SYSINIT) == 0 && a->pid == 0) {
973 /* run_actions(RESPAWN | ASKFIRST); */
974 /* - we return to main loop, which does this automagically */
978 static int check_delayed_sigs(void)
983 smallint sig = bb_got_signal;
989 #if ENABLE_FEATURE_USE_INITTAB
994 run_actions(CTRLALTDEL);
995 if (sig == SIGQUIT) {
996 exec_restart_action();
997 /* returns only if no restart action defined */
1007 halt_reboot_pwoff(sig);
1012 #if DEBUG_SEGV_HANDLER
1014 void handle_sigsegv(int sig, siginfo_t *info, void *ucontext)
1020 ip = uc->uc_mcontext.gregs[REG_EIP];
1021 fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n",
1023 /* this is void*, but using %p would print "(null)"
1024 * even for ptrs which are not exactly 0, but, say, 0x123:
1026 (long)info->si_addr,
1029 /* glibc extension */
1032 size = backtrace(array, 50);
1033 backtrace_symbols_fd(array, size, 2);
1035 for (;;) sleep(9999);
1039 static void sleep_much(void)
1041 sleep(30 * 24*60*60);
1044 int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1045 int init_main(int argc UNUSED_PARAM, char **argv)
1047 if (argv[1] && strcmp(argv[1], "-q") == 0) {
1048 return kill(1, SIGHUP);
1051 #if DEBUG_SEGV_HANDLER
1053 struct sigaction sa;
1054 memset(&sa, 0, sizeof(sa));
1055 sa.sa_sigaction = handle_sigsegv;
1056 sa.sa_flags = SA_SIGINFO;
1057 sigaction(SIGSEGV, &sa, NULL);
1058 sigaction(SIGILL, &sa, NULL);
1059 sigaction(SIGFPE, &sa, NULL);
1060 sigaction(SIGBUS, &sa, NULL);
1065 /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
1067 && (!ENABLE_LINUXRC || applet_name[0] != 'l') /* not linuxrc? */
1069 bb_error_msg_and_die("must be run as PID 1");
1071 #ifdef RB_DISABLE_CAD
1072 /* Turn off rebooting via CTL-ALT-DEL - we get a
1073 * SIGINT on CAD so we can shut things down gracefully... */
1074 reboot(RB_DISABLE_CAD); /* misnomer */
1078 /* If, say, xmalloc would ever die, we don't want to oops kernel
1080 * NB: we set die_func *after* PID 1 check and bb_show_usage.
1081 * Otherwise, for example, "init u" ("please rexec yourself"
1082 * command for sysvinit) will show help text (which isn't too bad),
1083 * *and sleep forever* (which is bad!)
1085 die_func = sleep_much;
1087 /* Figure out where the default console should be */
1093 /* Make sure environs is set to something sane */
1094 putenv((char *) "HOME=/");
1095 putenv((char *) bb_PATH_root_path);
1096 putenv((char *) "SHELL=/bin/sh");
1097 putenv((char *) "USER=root"); /* needed? why? */
1100 xsetenv("RUNLEVEL", argv[1]);
1102 #if !ENABLE_FEATURE_INIT_QUIET
1104 message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
1108 /* It's 2013, does anyone really still depend on this? */
1109 /* If you do, consider adding swapon to sysinit actions then! */
1110 /* struct sysinfo is linux-specific */
1112 /* Make sure there is enough memory to do something useful. */
1113 /*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ {
1114 struct sysinfo info;
1116 if (sysinfo(&info) == 0
1117 && (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024
1119 message(L_CONSOLE, "Low memory, forcing swapon");
1120 /* swapon -a requires /proc typically */
1121 new_init_action(SYSINIT, "mount -t proc proc /proc", "");
1122 /* Try to turn on swap */
1123 new_init_action(SYSINIT, "swapon -a", "");
1124 run_actions(SYSINIT); /* wait and removing */
1130 /* Check if we are supposed to be in single user mode */
1132 && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
1134 /* ??? shouldn't we set RUNLEVEL="b" here? */
1135 /* Start a shell on console */
1136 new_init_action(RESPAWN, bb_default_login_shell, "");
1138 /* Not in single user mode - see what inittab says */
1140 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
1141 * then parse_inittab() simply adds in some default
1142 * actions (i.e., INIT_SCRIPT and a pair
1143 * of "askfirst" shells) */
1148 if (getenv("SELINUX_INIT") == NULL) {
1151 putenv((char*)"SELINUX_INIT=YES");
1152 if (selinux_init_load_policy(&enforce) == 0) {
1153 BB_EXECVP(argv[0], argv);
1154 } else if (enforce > 0) {
1155 /* SELinux in enforcing mode but load_policy failed */
1156 message(L_CONSOLE, "can't load SELinux Policy. "
1157 "Machine is in enforcing mode. Halting now.");
1158 return EXIT_FAILURE;
1163 if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE) {
1164 /* Make the command line just say "init" - that's all, nothing else */
1165 strncpy(argv[0], "init", strlen(argv[0]));
1166 /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
1171 /* Set up signal handlers */
1173 struct sigaction sa;
1175 /* Stop handler must allow only SIGCONT inside itself */
1176 memset(&sa, 0, sizeof(sa));
1177 sigfillset(&sa.sa_mask);
1178 sigdelset(&sa.sa_mask, SIGCONT);
1179 sa.sa_handler = stop_handler;
1180 /* NB: sa_flags doesn't have SA_RESTART.
1181 * It must be able to interrupt wait().
1183 sigaction_set(SIGTSTP, &sa); /* pause */
1184 /* Does not work as intended, at least in 2.6.20.
1185 * SIGSTOP is simply ignored by init:
1187 sigaction_set(SIGSTOP, &sa); /* pause */
1189 /* These signals must interrupt wait(),
1190 * setting handler without SA_RESTART flag.
1192 bb_signals_recursive_norestart(0
1193 + (1 << SIGINT) /* Ctrl-Alt-Del */
1194 + (1 << SIGQUIT) /* re-exec another init */
1196 + (1 << SIGPWR) /* halt */
1198 + (1 << SIGUSR1) /* halt */
1199 + (1 << SIGTERM) /* reboot */
1200 + (1 << SIGUSR2) /* poweroff */
1201 #if ENABLE_FEATURE_USE_INITTAB
1202 + (1 << SIGHUP) /* reread /etc/inittab */
1207 /* Now run everything that needs to be run */
1208 /* First run the sysinit command */
1209 run_actions(SYSINIT);
1210 check_delayed_sigs();
1211 /* Next run anything that wants to block */
1213 check_delayed_sigs();
1214 /* Next run anything to be run only once */
1217 /* Now run the looping stuff for the rest of forever.
1222 maybe_WNOHANG = check_delayed_sigs();
1224 /* (Re)run the respawn/askfirst stuff */
1225 run_actions(RESPAWN | ASKFIRST);
1226 maybe_WNOHANG |= check_delayed_sigs();
1228 /* Don't consume all CPU time - sleep a bit */
1230 maybe_WNOHANG |= check_delayed_sigs();
1232 /* Wait for any child process(es) to exit.
1234 * If check_delayed_sigs above reported that a signal
1235 * was caught, wait will be nonblocking. This ensures
1236 * that if SIGHUP has reloaded inittab, respawn and askfirst
1237 * actions will not be delayed until next child death.
1240 maybe_WNOHANG = WNOHANG;
1243 struct init_action *a;
1245 /* If signals happen _in_ the wait, they interrupt it,
1246 * bb_signals_recursive_norestart set them up that way
1248 wpid = waitpid(-1, NULL, maybe_WNOHANG);
1252 a = mark_terminated(wpid);
1254 message(L_LOG, "process '%s' (pid %d) exited. "
1255 "Scheduling for restart.",
1258 /* See if anyone else is waiting to be reaped */
1259 maybe_WNOHANG = WNOHANG;
1264 //usage:#define linuxrc_trivial_usage NOUSAGE_STR
1265 //usage:#define linuxrc_full_usage ""
1267 //usage:#define init_trivial_usage
1269 //usage:#define init_full_usage "\n\n"
1270 //usage: "Init is the first process started during boot. It never exits."
1271 //usage: IF_FEATURE_USE_INITTAB(
1272 //usage: "\n""It (re)spawns children according to /etc/inittab."
1274 //usage: IF_NOT_FEATURE_USE_INITTAB(
1275 //usage: "\n""This version of init doesn't use /etc/inittab,"
1276 //usage: "\n""has fixed set of processed to run."
1279 //usage:#define init_notes_usage
1280 //usage: "This version of init is designed to be run only by the kernel.\n"
1282 //usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
1283 //usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
1284 //usage: "runlevels, use sysvinit.\n"
1286 //usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n"
1287 //usage: "it has the following default behavior:\n"
1289 //usage: " ::sysinit:/etc/init.d/rcS\n"
1290 //usage: " ::askfirst:/bin/sh\n"
1291 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1292 //usage: " ::shutdown:/sbin/swapoff -a\n"
1293 //usage: " ::shutdown:/bin/umount -a -r\n"
1294 //usage: " ::restart:/sbin/init\n"
1295 //usage: " tty2::askfirst:/bin/sh\n"
1296 //usage: " tty3::askfirst:/bin/sh\n"
1297 //usage: " tty4::askfirst:/bin/sh\n"
1299 //usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
1301 //usage: " <id>:<runlevels>:<action>:<process>\n"
1305 //usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n"
1306 //usage: " The id field is used by BusyBox init to specify the controlling tty for\n"
1307 //usage: " the specified process to run on. The contents of this field are\n"
1308 //usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n"
1309 //usage: " be unique, although if it isn't you may have strange results. If this\n"
1310 //usage: " field is left blank, then the init's stdin/out will be used.\n"
1312 //usage: " <runlevels>:\n"
1314 //usage: " The runlevels field is completely ignored.\n"
1316 //usage: " <action>:\n"
1318 //usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n"
1319 //usage: " once, restart, ctrlaltdel, and shutdown.\n"
1321 //usage: " The available actions can be classified into two groups: actions\n"
1322 //usage: " that are run only once, and actions that are re-run when the specified\n"
1323 //usage: " process exits.\n"
1325 //usage: " Run only-once actions:\n"
1327 //usage: " 'sysinit' is the first item run on boot. init waits until all\n"
1328 //usage: " sysinit actions are completed before continuing. Following the\n"
1329 //usage: " completion of all sysinit actions, all 'wait' actions are run.\n"
1330 //usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n"
1331 //usage: " the specified task completes. 'once' actions are asynchronous,\n"
1332 //usage: " therefore, init does not wait for them to complete. 'restart' is\n"
1333 //usage: " the action taken to restart the init process. By default this should\n"
1334 //usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n"
1335 //usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
1336 //usage: " actions are run when the system detects that someone on the system\n"
1337 //usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
1338 //usage: " wants to run 'reboot' at this point to cause the system to reboot.\n"
1339 //usage: " Finally the 'shutdown' action specifies the actions to taken when\n"
1340 //usage: " init is told to reboot. Unmounting filesystems and disabling swap\n"
1341 //usage: " is a very good here.\n"
1343 //usage: " Run repeatedly actions:\n"
1345 //usage: " 'respawn' actions are run after the 'once' actions. When a process\n"
1346 //usage: " started with a 'respawn' action exits, init automatically restarts\n"
1347 //usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n"
1348 //usage: " respawning out of control. The 'askfirst' actions acts just like\n"
1349 //usage: " respawn, except that before running the specified process it\n"
1350 //usage: " displays the line \"Please press Enter to activate this console.\"\n"
1351 //usage: " and then waits for the user to press enter before starting the\n"
1352 //usage: " specified process.\n"
1354 //usage: " Unrecognized actions (like initdefault) will cause init to emit an\n"
1355 //usage: " error message, and then go along with its business. All actions are\n"
1356 //usage: " run in the order they appear in /etc/inittab.\n"
1358 //usage: " <process>:\n"
1360 //usage: " Specifies the process to be executed and its command line.\n"
1362 //usage: "Example /etc/inittab file:\n"
1364 //usage: " # This is run first except when booting in single-user mode\n"
1366 //usage: " ::sysinit:/etc/init.d/rcS\n"
1368 //usage: " # /bin/sh invocations on selected ttys\n"
1370 //usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n"
1371 //usage: " ::askfirst:-/bin/sh\n"
1372 //usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n"
1373 //usage: " tty2::askfirst:-/bin/sh\n"
1374 //usage: " tty3::askfirst:-/bin/sh\n"
1375 //usage: " tty4::askfirst:-/bin/sh\n"
1377 //usage: " # /sbin/getty invocations for selected ttys\n"
1379 //usage: " tty4::respawn:/sbin/getty 38400 tty4\n"
1380 //usage: " tty5::respawn:/sbin/getty 38400 tty5\n"
1383 //usage: " # Example of how to put a getty on a serial line (for a terminal)\n"
1385 //usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
1386 //usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
1388 //usage: " # Example how to put a getty on a modem line\n"
1389 //usage: " #::respawn:/sbin/getty 57600 ttyS2\n"
1391 //usage: " # Stuff to do when restarting the init process\n"
1392 //usage: " ::restart:/sbin/init\n"
1394 //usage: " # Stuff to do before rebooting\n"
1395 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1396 //usage: " ::shutdown:/bin/umount -a -r\n"
1397 //usage: " ::shutdown:/sbin/swapoff -a\n"