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 //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
13 //applet:IF_FEATURE_INITRD(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
15 //kbuild:lib-$(CONFIG_INIT) += init.o
20 //config: select FEATURE_SYSLOG
22 //config: init is the first program run when the system boots.
24 //config:config FEATURE_USE_INITTAB
25 //config: bool "Support reading an inittab file"
27 //config: depends on INIT
29 //config: Allow init to read an inittab file when the system boot.
31 //config:config FEATURE_KILL_REMOVED
32 //config: bool "Support killing processes that have been removed from inittab"
34 //config: depends on FEATURE_USE_INITTAB
36 //config: When respawn entries are removed from inittab and a SIGHUP is
37 //config: sent to init, this option will make init kill the processes
38 //config: that have been removed.
40 //config:config FEATURE_KILL_DELAY
41 //config: int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED
42 //config: range 0 1024
44 //config: depends on FEATURE_KILL_REMOVED
46 //config: With nonzero setting, init sends TERM, forks, child waits N
47 //config: seconds, sends KILL and exits. Setting it too high is unwise
48 //config: (child will hang around for too long and could actually kill
49 //config: the wrong process!)
51 //config:config FEATURE_INIT_SCTTY
52 //config: bool "Run commands with leading dash with controlling tty"
54 //config: depends on INIT
56 //config: If this option is enabled, init will try to give a controlling
57 //config: tty to any command which has leading hyphen (often it's "-/bin/sh").
58 //config: More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)".
59 //config: If device attached to STDIN_FILENO can be a ctty but is not yet
60 //config: a ctty for other session, it will become this process' ctty.
61 //config: This is not the traditional init behavour, but is often what you want
62 //config: in an embedded system where the console is only accessed during
63 //config: development or for maintenance.
64 //config: NB: using cttyhack applet may work better.
66 //config:config FEATURE_INIT_SYSLOG
67 //config: bool "Enable init to write to syslog"
69 //config: depends on INIT
71 //config:config FEATURE_EXTRA_QUIET
72 //config: bool "Be _extra_ quiet on boot"
74 //config: depends on INIT
76 //config: Prevent init from logging some messages to the console during boot.
78 //config:config FEATURE_INIT_COREDUMPS
79 //config: bool "Support dumping core for child processes (debugging only)"
81 //config: depends on INIT
83 //config: If this option is enabled and the file /.init_enable_core
84 //config: exists, then init will call setrlimit() to allow unlimited
85 //config: core file sizes. If this option is disabled, processes
86 //config: will not generate any core files.
88 //config:config FEATURE_INITRD
89 //config: bool "Support running init from within an initrd (not initramfs)"
91 //config: depends on INIT
93 //config: Legacy support for running init under the old-style initrd. Allows
94 //config: the name linuxrc to act as init, and it doesn't assume init is PID 1.
96 //config: This does not apply to initramfs, which runs /init as PID 1 and
97 //config: requires no special support.
99 //config:config INIT_TERMINAL_TYPE
100 //config: string "Initial terminal type"
101 //config: default "linux"
102 //config: depends on INIT
104 //config: This is the initial value set by init for the TERM environment
105 //config: variable. This variable is used by programs which make use of
106 //config: extended terminal capabilities.
108 //config: Note that on Linux, init attempts to detect serial terminal and
109 //config: sets TERM to "vt102" if one is found.
114 #include <sys/resource.h>
116 #include <linux/vt.h>
118 #include "reboot.h" /* reboot() constants */
120 /* Used only for sanitizing purposes in set_sane_term() below. On systems where
121 * the baud rate is stored in a separate field, we can safely disable them. */
127 /* Was a CONFIG_xxx option. A lot of people were building
128 * not fully functional init by switching it on! */
131 #define COMMAND_SIZE 256
132 #define CONSOLE_NAME_SIZE 32
134 /* Default sysinit script. */
136 #define INIT_SCRIPT "/etc/init.d/rcS"
139 /* Each type of actions can appear many times. They will be
140 * handled in order. RESTART is an exception, only 1st is used.
142 /* Start these actions first and wait for completion */
144 /* Start these after SYSINIT and wait for completion */
146 /* Start these after WAIT and *dont* wait for completion */
149 * NB: while SYSINIT/WAIT/ONCE are being processed,
150 * SIGHUP ("reread /etc/inittab") will be processed only after
151 * each group of actions. If new inittab adds, say, a SYSINIT action,
152 * it will not be run, since init is already "past SYSINIT stage".
154 /* Start these after ONCE are started, restart on exit */
156 /* Like RESPAWN, but wait for <Enter> to be pressed on tty */
157 #define ASKFIRST 0x10
159 * Start these on SIGINT, and wait for completion.
160 * Then go back to respawning RESPAWN and ASKFIRST actions.
161 * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
163 #define CTRLALTDEL 0x20
165 * Start these before killing all processes in preparation for
166 * running RESTART actions or doing low-level halt/reboot/poweroff
167 * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
168 * Wait for completion before proceeding.
170 #define SHUTDOWN 0x40
172 * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
173 * then all processes are killed, then init exec's 1st RESTART action,
174 * replacing itself by it. If no RESTART action specified,
175 * SIGQUIT has no effect.
180 /* A linked list of init_actions, to be read from inittab */
182 struct init_action *next;
185 char terminal[CONSOLE_NAME_SIZE];
186 char command[COMMAND_SIZE];
189 static struct init_action *init_action_list = NULL;
191 static const char *log_console = VC_5;
198 /* Print a message to the specified device.
199 * "where" may be bitwise-or'd from L_LOG | L_CONSOLE
200 * NB: careful, we can be called after vfork!
202 #define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
203 static void message(int where, const char *fmt, ...)
204 __attribute__ ((format(printf, 2, 3)));
205 static void message(int where, const char *fmt, ...)
212 va_start(arguments, fmt);
213 l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments);
214 if (l > sizeof(msg) - 1)
218 #if ENABLE_FEATURE_INIT_SYSLOG
221 /* Log the message to syslogd */
222 openlog(applet_name, 0, LOG_DAEMON);
223 /* don't print "\r" */
224 syslog(LOG_INFO, "%s", msg + 1);
231 static int log_fd = -1;
235 /* Take full control of the log tty, and never close it.
236 * It's mine, all mine! Muhahahaha! */
239 log_fd = STDERR_FILENO;
241 log_fd = device_open(log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY);
243 bb_error_msg("can't log to %s", log_console);
246 close_on_exec_on(log_fd);
251 full_write(log_fd, msg, l);
252 if (log_fd == STDERR_FILENO)
253 return; /* don't print dup messages */
258 if (where & L_CONSOLE) {
259 /* Send console messages to console so people will see them. */
260 full_write(STDERR_FILENO, msg, l);
264 static void console_init(void)
271 s = getenv("CONSOLE");
273 s = getenv("console");
275 int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY);
277 dup2(fd, STDIN_FILENO);
278 dup2(fd, STDOUT_FILENO);
279 xmove_fd(fd, STDERR_FILENO);
281 dbg_message(L_LOG, "console='%s'", s);
283 /* Make sure fd 0,1,2 are not closed
284 * (so that they won't be used by future opens) */
286 // Users report problems
287 // /* Make sure init can't be blocked by writing to stderr */
288 // fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK);
293 if (ioctl(STDIN_FILENO, VT_OPENQRY, &vtno) != 0) {
294 /* Not a linux terminal, probably serial console.
295 * Force the TERM setting to vt102
296 * if TERM is set to linux (the default) */
297 if (!s || strcmp(s, "linux") == 0)
298 putenv((char*)"TERM=vt102");
299 if (!ENABLE_FEATURE_INIT_SYSLOG)
304 putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE);
307 /* Set terminal settings to reasonable defaults.
308 * NB: careful, we can be called after vfork! */
309 static void set_sane_term(void)
313 tcgetattr(STDIN_FILENO, &tty);
315 /* set control chars */
316 tty.c_cc[VINTR] = 3; /* C-c */
317 tty.c_cc[VQUIT] = 28; /* C-\ */
318 tty.c_cc[VERASE] = 127; /* C-? */
319 tty.c_cc[VKILL] = 21; /* C-u */
320 tty.c_cc[VEOF] = 4; /* C-d */
321 tty.c_cc[VSTART] = 17; /* C-q */
322 tty.c_cc[VSTOP] = 19; /* C-s */
323 tty.c_cc[VSUSP] = 26; /* C-z */
326 /* use line discipline 0 */
330 /* Make it be sane */
334 /* added CRTSCTS to fix Debian bug 528560 */
335 tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS;
336 tty.c_cflag |= CREAD | HUPCL | CLOCAL;
339 tty.c_iflag = ICRNL | IXON | IXOFF;
342 tty.c_oflag = OPOST | ONLCR;
345 tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN;
347 tcsetattr_stdin_TCSANOW(&tty);
350 /* Open the new terminal device.
351 * NB: careful, we can be called after vfork! */
352 static int open_stdio_to_tty(const char* tty_name)
354 /* empty tty_name means "use init's tty", else... */
359 /* fd can be only < 0 or 0: */
360 fd = device_open(tty_name, O_RDWR);
362 message(L_LOG | L_CONSOLE, "can't open %s: %s",
363 tty_name, strerror(errno));
364 return 0; /* failure */
366 dup2(STDIN_FILENO, STDOUT_FILENO);
367 dup2(STDIN_FILENO, STDERR_FILENO);
370 return 1; /* success */
373 static void reset_sighandlers_and_unblock_sigs(void)
385 sigprocmask_allsigs(SIG_UNBLOCK);
388 /* Wrapper around exec:
389 * Takes string (max COMMAND_SIZE chars).
390 * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
391 * Otherwise splits words on whitespace, deals with leading dash,
392 * and uses plain exec().
393 * NB: careful, we can be called after vfork!
395 static void init_exec(const char *command)
397 char *cmd[COMMAND_SIZE / 2];
398 char buf[COMMAND_SIZE + 6]; /* COMMAND_SIZE+strlen("exec ")+1 */
399 int dash = (command[0] == '-' /* maybe? && command[1] == '/' */);
403 /* See if any special /bin/sh requiring characters are present */
404 if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
405 sprintf(buf, "exec %s", command); /* excluding "-" */
406 /* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
407 cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash);
408 cmd[1] = (char*)"-c";
411 command = LIBBB_DEFAULT_LOGIN_SHELL + 1;
413 /* Convert command (char*) into cmd (char**, one word per string) */
416 next = strcpy(buf, command - dash); /* command including "-" */
417 while ((word = strsep(&next, " \t")) != NULL) {
418 if (*word != '\0') { /* not two spaces/tabs together? */
425 /* If we saw leading "-", it is interactive shell.
426 * Try harder to give it a controlling tty.
428 if (ENABLE_FEATURE_INIT_SCTTY && dash) {
429 /* _Attempt_ to make stdin a controlling tty. */
430 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/);
432 /* Here command never contains the dash, cmd[0] might */
433 BB_EXECVP(command, cmd);
434 message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno));
435 /* returns if execvp fails */
438 /* Used only by run_actions */
439 static pid_t run(const struct init_action *a)
443 /* Careful: don't be affected by a signal in vforked child */
444 sigprocmask_allsigs(SIG_BLOCK);
445 if (BB_MMU && (a->action_type & ASKFIRST))
450 message(L_LOG | L_CONSOLE, "can't fork");
452 sigprocmask_allsigs(SIG_UNBLOCK);
453 return pid; /* Parent or error */
458 /* Reset signal handlers that were set by the parent process */
459 reset_sighandlers_and_unblock_sigs();
461 /* Create a new session and make ourself the process group leader */
464 /* Open the new terminal device */
465 if (!open_stdio_to_tty(a->terminal))
468 /* NB: on NOMMU we can't wait for input in child, so
469 * "askfirst" will work the same as "respawn". */
470 if (BB_MMU && (a->action_type & ASKFIRST)) {
471 static const char press_enter[] ALIGN1 =
472 #ifdef CUSTOMIZED_BANNER
473 #include CUSTOMIZED_BANNER
475 "\nPlease press Enter to activate this console. ";
478 * Save memory by not exec-ing anything large (like a shell)
479 * before the user wants it. This is critical if swap is not
480 * enabled and the system has low memory. Generally this will
481 * be run on the second virtual console, and the first will
482 * be allowed to start a shell or whatever an init script
485 dbg_message(L_LOG, "waiting for enter to start '%s'"
486 "(pid %d, tty '%s')\n",
487 a->command, getpid(), a->terminal);
488 full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1);
489 while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n')
494 * When a file named /.init_enable_core exists, setrlimit is called
495 * before processes are spawned to set core file size as unlimited.
496 * This is for debugging only. Don't use this is production, unless
497 * you want core dumps lying about....
499 if (ENABLE_FEATURE_INIT_COREDUMPS) {
500 if (access("/.init_enable_core", F_OK) == 0) {
502 limit.rlim_cur = RLIM_INFINITY;
503 limit.rlim_max = RLIM_INFINITY;
504 setrlimit(RLIMIT_CORE, &limit);
508 /* Log the process name and args */
509 message(L_LOG, "starting pid %d, tty '%s': '%s'",
510 getpid(), a->terminal, a->command);
512 /* Now run it. The new program will take over this PID,
513 * so nothing further in init.c should be run. */
514 init_exec(a->command);
515 /* We're still here? Some error happened. */
519 static struct init_action *mark_terminated(pid_t pid)
521 struct init_action *a;
524 for (a = init_action_list; a; a = a->next) {
530 update_utmp(pid, DEAD_PROCESS, /*tty_name:*/ NULL,
537 static void waitfor(pid_t pid)
539 /* waitfor(run(x)): protect against failed fork inside run() */
543 /* Wait for any child (prevent zombies from exiting orphaned processes)
544 * but exit the loop only when specified one has exited. */
546 pid_t wpid = wait(NULL);
547 mark_terminated(wpid);
548 /* Unsafe. SIGTSTP handler might have wait'ed it already */
549 /*if (wpid == pid) break;*/
556 /* Run all commands of a particular type */
557 static void run_actions(int action_type)
559 struct init_action *a;
561 for (a = init_action_list; a; a = a->next) {
562 if (!(a->action_type & action_type))
565 if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
567 if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
570 if (a->action_type & (RESPAWN | ASKFIRST)) {
571 /* Only run stuff with pid == 0. If pid != 0,
572 * it is already running
580 static void new_init_action(uint8_t action_type, const char *command, const char *cons)
582 struct init_action *a, **nextp;
586 * ::shutdown:umount -a -r
587 * ::shutdown:swapoff -a
589 * ::shutdown:swapoff -a
590 * ::shutdown:umount -a -r
591 * On reload, we must ensure entries end up in correct order.
592 * To achieve that, if we find a matching entry, we move it
595 nextp = &init_action_list;
596 while ((a = *nextp) != NULL) {
597 /* Don't enter action if it's already in the list,
598 * This prevents losing running RESPAWNs.
600 if (strcmp(a->command, command) == 0
601 && strcmp(a->terminal, cons) == 0
603 /* Remove from list */
605 /* Find the end of the list */
606 while (*nextp != NULL)
607 nextp = &(*nextp)->next;
615 a = xzalloc(sizeof(*a));
616 /* Append to the end of the list */
618 a->action_type = action_type;
619 safe_strncpy(a->command, command, sizeof(a->command));
620 safe_strncpy(a->terminal, cons, sizeof(a->terminal));
621 dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%d tty='%s'\n",
622 a->command, a->action_type, a->terminal);
625 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
626 * then parse_inittab() simply adds in some default
627 * actions(i.e., runs INIT_SCRIPT and then starts a pair
628 * of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB
629 * _is_ defined, but /etc/inittab is missing, this
630 * results in the same set of default behaviors.
632 static void parse_inittab(void)
634 #if ENABLE_FEATURE_USE_INITTAB
636 parser_t *parser = config_open2("/etc/inittab", fopen_for_read);
641 /* No inittab file - set up some default behavior */
642 /* Reboot on Ctrl-Alt-Del */
643 new_init_action(CTRLALTDEL, "reboot", "");
644 /* Umount all filesystems on halt/reboot */
645 new_init_action(SHUTDOWN, "umount -a -r", "");
646 /* Swapoff on halt/reboot */
647 if (ENABLE_SWAPONOFF)
648 new_init_action(SHUTDOWN, "swapoff -a", "");
649 /* Prepare to restart init when a QUIT is received */
650 new_init_action(RESTART, "init", "");
651 /* Askfirst shell on tty1-4 */
652 new_init_action(ASKFIRST, bb_default_login_shell, "");
653 //TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
654 new_init_action(ASKFIRST, bb_default_login_shell, VC_2);
655 new_init_action(ASKFIRST, bb_default_login_shell, VC_3);
656 new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
658 new_init_action(SYSINIT, INIT_SCRIPT, "");
662 #if ENABLE_FEATURE_USE_INITTAB
663 /* optional_tty:ignored_runlevel:action:command
664 * Delims are not to be collapsed and need exactly 4 tokens
666 while (config_read(parser, token, 4, 0, "#:",
667 PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
668 /* order must correspond to SYSINIT..RESTART constants */
669 static const char actions[] ALIGN1 =
670 "sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
671 "ctrlaltdel\0""shutdown\0""restart\0";
673 char *tty = token[0];
675 if (!token[3]) /* less than 4 tokens */
677 action = index_in_strings(actions, token[2]);
678 if (action < 0 || !token[3][0]) /* token[3]: command */
680 /* turn .*TTY -> /dev/TTY */
682 tty = concat_path_file("/dev/", skip_dev_pfx(tty));
684 new_init_action(1 << action, token[3], tty);
689 message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d",
692 config_close(parser);
696 static void pause_and_low_level_reboot(unsigned magic) NORETURN;
697 static void pause_and_low_level_reboot(unsigned magic)
701 /* Allow time for last message to reach serial console, etc */
704 /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
705 * in linux/kernel/sys.c, which can cause the machine to panic when
706 * the init process exits... */
708 if (pid == 0) { /* child */
716 static void run_shutdown_and_kill_processes(void)
718 /* Run everything to be run at "shutdown". This is done _prior_
719 * to killing everything, in case people wish to use scripts to
720 * shut things down gracefully... */
721 run_actions(SHUTDOWN);
723 message(L_CONSOLE | L_LOG, "The system is going down NOW!");
725 /* Send signals to every process _except_ pid 1 */
727 message(L_CONSOLE | L_LOG, "Sent SIG%s to all processes", "TERM");
732 message(L_CONSOLE, "Sent SIG%s to all processes", "KILL");
734 /*sleep(1); - callers take care about making a pause */
737 /* Signal handling by init:
739 * For process with PID==1, on entry kernel sets all signals to SIG_DFL
740 * and unmasks all signals. However, for process with PID==1,
741 * default action (SIG_DFL) on any signal is to ignore it,
742 * even for special signals SIGKILL and SIGCONT.
743 * Also, any signal can be caught or blocked.
744 * (but SIGSTOP is still handled specially, at least in 2.6.20)
746 * We install two kinds of handlers, "immediate" and "delayed".
748 * Immediate handlers execute at any time, even while, say, sysinit
751 * Delayed handlers just set a flag variable. The variable is checked
752 * in the main loop and acted upon.
754 * halt/poweroff/reboot and restart have immediate handlers.
755 * They only traverse linked list of struct action's, never modify it,
756 * this should be safe to do even in signal handler. Also they
759 * SIGSTOP and SIGTSTP have immediate handlers. They just wait
760 * for SIGCONT to happen.
762 * SIGHUP has a delayed handler, because modifying linked list
763 * of struct action's from a signal handler while it is manipulated
764 * by the program may be disastrous.
766 * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
767 * it to happen even somewhere inside "sysinit" would be a bit awkward.
769 * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
770 * and only one will be remembered and acted upon.
773 /* The SIGUSR[12]/SIGTERM handler */
774 static void halt_reboot_pwoff(int sig) NORETURN;
775 static void halt_reboot_pwoff(int sig)
780 /* We may call run() and it unmasks signals,
781 * including the one masked inside this signal handler.
782 * Testcase which would start multiple reboot scripts:
783 * while true; do reboot; done
786 reset_sighandlers_and_unblock_sigs();
788 run_shutdown_and_kill_processes();
792 if (sig == SIGTERM) {
795 } else if (sig == SIGUSR2) {
799 message(L_CONSOLE, "Requesting system %s", m);
800 pause_and_low_level_reboot(rb);
804 /* Handler for QUIT - exec "restart" action,
805 * else (no such action defined) do nothing */
806 static void restart_handler(int sig UNUSED_PARAM)
808 struct init_action *a;
810 for (a = init_action_list; a; a = a->next) {
811 if (!(a->action_type & RESTART))
814 /* Starting from here, we won't return.
815 * Thus don't need to worry about preserving errno
819 reset_sighandlers_and_unblock_sigs();
821 run_shutdown_and_kill_processes();
824 /* Allow Ctrl-Alt-Del to reboot the system.
825 * This is how kernel sets it up for init, we follow suit.
827 reboot(RB_ENABLE_CAD); /* misnomer */
830 if (open_stdio_to_tty(a->terminal)) {
831 dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
832 /* Theoretically should be safe.
833 * But in practice, kernel bugs may leave
834 * unkillable processes, and wait() may block forever.
835 * Oh well. Hoping "new" init won't be too surprised
836 * by having children it didn't create.
838 //while (wait(NULL) > 0)
840 init_exec(a->command);
842 /* Open or exec failed */
843 pause_and_low_level_reboot(RB_HALT_SYSTEM);
848 /* The SIGSTOP/SIGTSTP handler
849 * NB: inside it, all signals except SIGCONT are masked
850 * via appropriate setup in sigaction().
852 static void stop_handler(int sig UNUSED_PARAM)
854 smallint saved_bb_got_signal;
857 saved_bb_got_signal = bb_got_signal;
859 signal(SIGCONT, record_signo);
864 if (bb_got_signal == SIGCONT)
866 /* NB: this can accidentally wait() for a process
867 * which we waitfor() elsewhere! waitfor() must have
868 * code which is resilient against this.
870 wpid = wait_any_nohang(NULL);
871 mark_terminated(wpid);
875 signal(SIGCONT, SIG_DFL);
877 bb_got_signal = saved_bb_got_signal;
880 #if ENABLE_FEATURE_USE_INITTAB
881 static void reload_inittab(void)
883 struct init_action *a, **nextp;
885 message(L_LOG, "reloading /etc/inittab");
887 /* Disable old entries */
888 for (a = init_action_list; a; a = a->next)
891 /* Append new entries, or modify existing entries
892 * (incl. setting a->action_type) if cmd and device name
893 * match new ones. End result: only entries with
894 * a->action_type == 0 are stale.
898 #if ENABLE_FEATURE_KILL_REMOVED
899 /* Kill stale entries */
900 /* Be nice and send SIGTERM first */
901 for (a = init_action_list; a; a = a->next)
902 if (a->action_type == 0 && a->pid != 0)
903 kill(a->pid, SIGTERM);
904 if (CONFIG_FEATURE_KILL_DELAY) {
905 /* NB: parent will wait in NOMMU case */
906 if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
907 sleep(CONFIG_FEATURE_KILL_DELAY);
908 for (a = init_action_list; a; a = a->next)
909 if (a->action_type == 0 && a->pid != 0)
910 kill(a->pid, SIGKILL);
916 /* Remove stale entries and SYSINIT entries.
917 * We never rerun SYSINIT entries anyway,
918 * removing them too saves a few bytes */
919 nextp = &init_action_list;
920 while ((a = *nextp) != NULL) {
921 if ((a->action_type & ~SYSINIT) == 0) {
930 /* run_actions(RESPAWN | ASKFIRST); */
931 /* - we return to main loop, which does this automagically */
935 static int check_delayed_sigs(void)
940 smallint sig = bb_got_signal;
946 #if ENABLE_FEATURE_USE_INITTAB
951 run_actions(CTRLALTDEL);
955 int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
956 int init_main(int argc UNUSED_PARAM, char **argv)
958 if (argv[1] && strcmp(argv[1], "-q") == 0) {
959 return kill(1, SIGHUP);
963 /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
965 && (!ENABLE_FEATURE_INITRD || applet_name[0] != 'l') /* not linuxrc? */
967 bb_error_msg_and_die("must be run as PID 1");
969 #ifdef RB_DISABLE_CAD
970 /* Turn off rebooting via CTL-ALT-DEL - we get a
971 * SIGINT on CAD so we can shut things down gracefully... */
972 reboot(RB_DISABLE_CAD); /* misnomer */
976 /* If, say, xmalloc would ever die, we don't want to oops kernel
978 * NB: we set die_sleep *after* PID 1 check and bb_show_usage.
979 * Otherwise, for example, "init u" ("please rexec yourself"
980 * command for sysvinit) will show help text (which isn't too bad),
981 * *and sleep forever* (which is bad!)
983 die_sleep = 30 * 24*60*60;
985 /* Figure out where the default console should be */
991 /* Make sure environs is set to something sane */
992 putenv((char *) "HOME=/");
993 putenv((char *) bb_PATH_root_path);
994 putenv((char *) "SHELL=/bin/sh");
995 putenv((char *) "USER=root"); /* needed? why? */
998 xsetenv("RUNLEVEL", argv[1]);
1000 #if !ENABLE_FEATURE_EXTRA_QUIET
1002 message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
1005 /* struct sysinfo is linux-specific */
1007 /* Make sure there is enough memory to do something useful. */
1008 if (ENABLE_SWAPONOFF) {
1009 struct sysinfo info;
1011 if (sysinfo(&info) == 0
1012 && (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024
1014 message(L_CONSOLE, "Low memory, forcing swapon");
1015 /* swapon -a requires /proc typically */
1016 new_init_action(SYSINIT, "mount -t proc proc /proc", "");
1017 /* Try to turn on swap */
1018 new_init_action(SYSINIT, "swapon -a", "");
1019 run_actions(SYSINIT); /* wait and removing */
1024 /* Check if we are supposed to be in single user mode */
1026 && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
1028 /* ??? shouldn't we set RUNLEVEL="b" here? */
1029 /* Start a shell on console */
1030 new_init_action(RESPAWN, bb_default_login_shell, "");
1032 /* Not in single user mode - see what inittab says */
1034 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
1035 * then parse_inittab() simply adds in some default
1036 * actions(i.e., INIT_SCRIPT and a pair
1037 * of "askfirst" shells */
1042 if (getenv("SELINUX_INIT") == NULL) {
1045 putenv((char*)"SELINUX_INIT=YES");
1046 if (selinux_init_load_policy(&enforce) == 0) {
1047 BB_EXECVP(argv[0], argv);
1048 } else if (enforce > 0) {
1049 /* SELinux in enforcing mode but load_policy failed */
1050 message(L_CONSOLE, "can't load SELinux Policy. "
1051 "Machine is in enforcing mode. Halting now.");
1052 return EXIT_FAILURE;
1057 /* Make the command line just say "init" - thats all, nothing else */
1058 strncpy(argv[0], "init", strlen(argv[0]));
1059 /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
1061 memset(*argv, 0, strlen(*argv));
1063 /* Set up signal handlers */
1065 struct sigaction sa;
1068 + (1 << SIGUSR1) /* halt */
1069 + (1 << SIGTERM) /* reboot */
1070 + (1 << SIGUSR2) /* poweroff */
1071 , halt_reboot_pwoff);
1072 signal(SIGQUIT, restart_handler); /* re-exec another init */
1074 /* Stop handler must allow only SIGCONT inside itself */
1075 memset(&sa, 0, sizeof(sa));
1076 sigfillset(&sa.sa_mask);
1077 sigdelset(&sa.sa_mask, SIGCONT);
1078 sa.sa_handler = stop_handler;
1079 /* NB: sa_flags doesn't have SA_RESTART.
1080 * It must be able to interrupt wait().
1082 sigaction_set(SIGTSTP, &sa); /* pause */
1083 /* Does not work as intended, at least in 2.6.20.
1084 * SIGSTOP is simply ignored by init:
1086 sigaction_set(SIGSTOP, &sa); /* pause */
1088 /* SIGINT (Ctrl-Alt-Del) must interrupt wait(),
1089 * setting handler without SA_RESTART flag.
1091 bb_signals_recursive_norestart((1 << SIGINT), record_signo);
1094 /* Set up "reread /etc/inittab" handler.
1095 * Handler is set up without SA_RESTART, it will interrupt syscalls.
1097 if (!DEBUG_INIT && ENABLE_FEATURE_USE_INITTAB)
1098 bb_signals_recursive_norestart((1 << SIGHUP), record_signo);
1100 /* Now run everything that needs to be run */
1101 /* First run the sysinit command */
1102 run_actions(SYSINIT);
1103 check_delayed_sigs();
1104 /* Next run anything that wants to block */
1106 check_delayed_sigs();
1107 /* Next run anything to be run only once */
1110 /* Now run the looping stuff for the rest of forever.
1115 maybe_WNOHANG = check_delayed_sigs();
1117 /* (Re)run the respawn/askfirst stuff */
1118 run_actions(RESPAWN | ASKFIRST);
1119 maybe_WNOHANG |= check_delayed_sigs();
1121 /* Don't consume all CPU time - sleep a bit */
1123 maybe_WNOHANG |= check_delayed_sigs();
1125 /* Wait for any child process(es) to exit.
1127 * If check_delayed_sigs above reported that a signal
1128 * was caught, wait will be nonblocking. This ensures
1129 * that if SIGHUP has reloaded inittab, respawn and askfirst
1130 * actions will not be delayed until next child death.
1133 maybe_WNOHANG = WNOHANG;
1136 struct init_action *a;
1138 /* If signals happen _in_ the wait, they interrupt it,
1139 * bb_signals_recursive_norestart set them up that way
1141 wpid = waitpid(-1, NULL, maybe_WNOHANG);
1145 a = mark_terminated(wpid);
1147 message(L_LOG, "process '%s' (pid %d) exited. "
1148 "Scheduling for restart.",
1151 /* See if anyone else is waiting to be reaped */
1152 maybe_WNOHANG = WNOHANG;
1157 //usage:#define linuxrc_trivial_usage NOUSAGE_STR
1158 //usage:#define linuxrc_full_usage ""
1160 //usage:#define init_trivial_usage
1162 //usage:#define init_full_usage "\n\n"
1163 //usage: "Init is the parent of all processes"
1165 //usage:#define init_notes_usage
1166 //usage: "This version of init is designed to be run only by the kernel.\n"
1168 //usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
1169 //usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
1170 //usage: "runlevels, use sysvinit.\n"
1172 //usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n"
1173 //usage: "it has the following default behavior:\n"
1175 //usage: " ::sysinit:/etc/init.d/rcS\n"
1176 //usage: " ::askfirst:/bin/sh\n"
1177 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1178 //usage: " ::shutdown:/sbin/swapoff -a\n"
1179 //usage: " ::shutdown:/bin/umount -a -r\n"
1180 //usage: " ::restart:/sbin/init\n"
1182 //usage: "if it detects that /dev/console is _not_ a serial console, it will also run:\n"
1184 //usage: " tty2::askfirst:/bin/sh\n"
1185 //usage: " tty3::askfirst:/bin/sh\n"
1186 //usage: " tty4::askfirst:/bin/sh\n"
1188 //usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
1190 //usage: " <id>:<runlevels>:<action>:<process>\n"
1194 //usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n"
1195 //usage: " The id field is used by BusyBox init to specify the controlling tty for\n"
1196 //usage: " the specified process to run on. The contents of this field are\n"
1197 //usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n"
1198 //usage: " be unique, although if it isn't you may have strange results. If this\n"
1199 //usage: " field is left blank, the controlling tty is set to the console. Also\n"
1200 //usage: " note that if BusyBox detects that a serial console is in use, then only\n"
1201 //usage: " entries whose controlling tty is either the serial console or /dev/null\n"
1202 //usage: " will be run. BusyBox init does nothing with utmp. We don't need no\n"
1203 //usage: " stinkin' utmp.\n"
1205 //usage: " <runlevels>:\n"
1207 //usage: " The runlevels field is completely ignored.\n"
1209 //usage: " <action>:\n"
1211 //usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n"
1212 //usage: " once, restart, ctrlaltdel, and shutdown.\n"
1214 //usage: " The available actions can be classified into two groups: actions\n"
1215 //usage: " that are run only once, and actions that are re-run when the specified\n"
1216 //usage: " process exits.\n"
1218 //usage: " Run only-once actions:\n"
1220 //usage: " 'sysinit' is the first item run on boot. init waits until all\n"
1221 //usage: " sysinit actions are completed before continuing. Following the\n"
1222 //usage: " completion of all sysinit actions, all 'wait' actions are run.\n"
1223 //usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n"
1224 //usage: " the specified task completes. 'once' actions are asynchronous,\n"
1225 //usage: " therefore, init does not wait for them to complete. 'restart' is\n"
1226 //usage: " the action taken to restart the init process. By default this should\n"
1227 //usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n"
1228 //usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
1229 //usage: " actions are run when the system detects that someone on the system\n"
1230 //usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
1231 //usage: " wants to run 'reboot' at this point to cause the system to reboot.\n"
1232 //usage: " Finally the 'shutdown' action specifies the actions to taken when\n"
1233 //usage: " init is told to reboot. Unmounting filesystems and disabling swap\n"
1234 //usage: " is a very good here.\n"
1236 //usage: " Run repeatedly actions:\n"
1238 //usage: " 'respawn' actions are run after the 'once' actions. When a process\n"
1239 //usage: " started with a 'respawn' action exits, init automatically restarts\n"
1240 //usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n"
1241 //usage: " respawning out of control. The 'askfirst' actions acts just like\n"
1242 //usage: " respawn, except that before running the specified process it\n"
1243 //usage: " displays the line \"Please press Enter to activate this console.\"\n"
1244 //usage: " and then waits for the user to press enter before starting the\n"
1245 //usage: " specified process.\n"
1247 //usage: " Unrecognized actions (like initdefault) will cause init to emit an\n"
1248 //usage: " error message, and then go along with its business. All actions are\n"
1249 //usage: " run in the order they appear in /etc/inittab.\n"
1251 //usage: " <process>:\n"
1253 //usage: " Specifies the process to be executed and its command line.\n"
1255 //usage: "Example /etc/inittab file:\n"
1257 //usage: " # This is run first except when booting in single-user mode\n"
1259 //usage: " ::sysinit:/etc/init.d/rcS\n"
1261 //usage: " # /bin/sh invocations on selected ttys\n"
1263 //usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n"
1264 //usage: " ::askfirst:-/bin/sh\n"
1265 //usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n"
1266 //usage: " tty2::askfirst:-/bin/sh\n"
1267 //usage: " tty3::askfirst:-/bin/sh\n"
1268 //usage: " tty4::askfirst:-/bin/sh\n"
1270 //usage: " # /sbin/getty invocations for selected ttys\n"
1272 //usage: " tty4::respawn:/sbin/getty 38400 tty4\n"
1273 //usage: " tty5::respawn:/sbin/getty 38400 tty5\n"
1276 //usage: " # Example of how to put a getty on a serial line (for a terminal)\n"
1278 //usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
1279 //usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
1281 //usage: " # Example how to put a getty on a modem line\n"
1282 //usage: " #::respawn:/sbin/getty 57600 ttyS2\n"
1284 //usage: " # Stuff to do when restarting the init process\n"
1285 //usage: " ::restart:/sbin/init\n"
1287 //usage: " # Stuff to do before rebooting\n"
1288 //usage: " ::ctrlaltdel:/sbin/reboot\n"
1289 //usage: " ::shutdown:/bin/umount -a -r\n"
1290 //usage: " ::shutdown:/sbin/swapoff -a\n"