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1/* vi: set sw=4 ts=4: */
2/*
3 * Mini init implementation for busybox
4 *
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.
8 *
9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
10 */
11
12//config:config INIT
13//config: bool "init"
14//config: default y
15//config: select FEATURE_SYSLOG
16//config: help
17//config: init is the first program run when the system boots.
18//config:
19//config:config LINUXRC
20//config: bool "Support running init from within an initrd (not initramfs)"
21//config: default y
22//config: select FEATURE_SYSLOG
23//config: help
24//config: Legacy support for running init under the old-style initrd. Allows
25//config: the name linuxrc to act as init, and it doesn't assume init is PID 1.
26//config:
27//config: This does not apply to initramfs, which runs /init as PID 1 and
28//config: requires no special support.
29//config:
30//config:config FEATURE_USE_INITTAB
31//config: bool "Support reading an inittab file"
32//config: default y
33//config: depends on INIT || LINUXRC
34//config: help
35//config: Allow init to read an inittab file when the system boot.
36//config:
37//config:config FEATURE_KILL_REMOVED
38//config: bool "Support killing processes that have been removed from inittab"
39//config: default n
40//config: depends on FEATURE_USE_INITTAB
41//config: help
42//config: When respawn entries are removed from inittab and a SIGHUP is
43//config: sent to init, this option will make init kill the processes
44//config: that have been removed.
45//config:
46//config:config FEATURE_KILL_DELAY
47//config: int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED
48//config: range 0 1024
49//config: default 0
50//config: depends on FEATURE_KILL_REMOVED
51//config: help
52//config: With nonzero setting, init sends TERM, forks, child waits N
53//config: seconds, sends KILL and exits. Setting it too high is unwise
54//config: (child will hang around for too long and could actually kill
55//config: the wrong process!)
56//config:
57//config:config FEATURE_INIT_SCTTY
58//config: bool "Run commands with leading dash with controlling tty"
59//config: default y
60//config: depends on INIT || LINUXRC
61//config: help
62//config: If this option is enabled, init will try to give a controlling
63//config: tty to any command which has leading hyphen (often it's "-/bin/sh").
64//config: More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)".
65//config: If device attached to STDIN_FILENO can be a ctty but is not yet
66//config: a ctty for other session, it will become this process' ctty.
67//config: This is not the traditional init behavour, but is often what you want
68//config: in an embedded system where the console is only accessed during
69//config: development or for maintenance.
70//config: NB: using cttyhack applet may work better.
71//config:
72//config:config FEATURE_INIT_SYSLOG
73//config: bool "Enable init to write to syslog"
74//config: default y
75//config: depends on INIT || LINUXRC
76//config:
77//config:config FEATURE_EXTRA_QUIET
78//config: bool "Be _extra_ quiet on boot"
79//config: default y
80//config: depends on INIT || LINUXRC
81//config: help
82//config: Prevent init from logging some messages to the console during boot.
83//config:
84//config:config FEATURE_INIT_COREDUMPS
85//config: bool "Support dumping core for child processes (debugging only)"
86//config: default n # not Y because this is a debug option
87//config: depends on INIT || LINUXRC
88//config: help
89//config: If this option is enabled and the file /.init_enable_core
90//config: exists, then init will call setrlimit() to allow unlimited
91//config: core file sizes. If this option is disabled, processes
92//config: will not generate any core files.
93//config:
94//config:config INIT_TERMINAL_TYPE
95//config: string "Initial terminal type"
96//config: default "linux"
97//config: depends on INIT || LINUXRC
98//config: help
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.
102//config:
103//config: Note that on Linux, init attempts to detect serial terminal and
104//config: sets TERM to "vt102" if one is found.
105//config:
106//config:config FEATURE_INIT_MODIFY_CMDLINE
107//config: bool "Modify the command-line to \"init\""
108//config: default y
109//config: depends on INIT || LINUXRC
110//config: help
111//config: When launched as PID 1 and after parsing its arguments, init
112//config: wipes all the arguments but argv[0] and rewrites argv[0] to
113//config: contain only "init", so that its command-line appears solely as
114//config: "init" in tools such as ps.
115//config: If this option is set to Y, init will keep its original behavior,
116//config: otherwise, all the arguments including argv[0] will be preserved,
117//config: be they parsed or ignored by init.
118//config: The original command-line used to launch init can then be
119//config: retrieved in /proc/1/cmdline on Linux, for example.
120
121//applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP))
122//applet:IF_LINUXRC(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc))
123
124//kbuild:lib-$(CONFIG_INIT) += init.o
125//kbuild:lib-$(CONFIG_LINUXRC) += init.o
126
127#define DEBUG_SEGV_HANDLER 0
128
129#include "libbb.h"
130#include <syslog.h>
131#include <sys/resource.h>
132#ifdef __linux__
133# include <linux/vt.h>
134# include <sys/sysinfo.h>
135#endif
136#include "reboot.h" /* reboot() constants */
137
138#if DEBUG_SEGV_HANDLER
139# undef _GNU_SOURCE
140# define _GNU_SOURCE 1
141# undef __USE_GNU
142# define __USE_GNU 1
143# include <execinfo.h>
144# include <sys/ucontext.h>
145#endif
146
147/* Used only for sanitizing purposes in set_sane_term() below. On systems where
148 * the baud rate is stored in a separate field, we can safely disable them. */
149#ifndef CBAUD
150# define CBAUD 0
151# define CBAUDEX 0
152#endif
153
154/* Was a CONFIG_xxx option. A lot of people were building
155 * not fully functional init by switching it on! */
156#define DEBUG_INIT 0
157
158#define CONSOLE_NAME_SIZE 32
159
160/* Default sysinit script. */
161#ifndef INIT_SCRIPT
162# define INIT_SCRIPT "/etc/init.d/rcS"
163#endif
164
165/* Each type of actions can appear many times. They will be
166 * handled in order. RESTART is an exception, only 1st is used.
167 */
168/* Start these actions first and wait for completion */
169#define SYSINIT 0x01
170/* Start these after SYSINIT and wait for completion */
171#define WAIT 0x02
172/* Start these after WAIT and *dont* wait for completion */
173#define ONCE 0x04
174/*
175 * NB: while SYSINIT/WAIT/ONCE are being processed,
176 * SIGHUP ("reread /etc/inittab") will be processed only after
177 * each group of actions. If new inittab adds, say, a SYSINIT action,
178 * it will not be run, since init is already "past SYSINIT stage".
179 */
180/* Start these after ONCE are started, restart on exit */
181#define RESPAWN 0x08
182/* Like RESPAWN, but wait for <Enter> to be pressed on tty */
183#define ASKFIRST 0x10
184/*
185 * Start these on SIGINT, and wait for completion.
186 * Then go back to respawning RESPAWN and ASKFIRST actions.
187 * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed.
188 */
189#define CTRLALTDEL 0x20
190/*
191 * Start these before killing all processes in preparation for
192 * running RESTART actions or doing low-level halt/reboot/poweroff
193 * (initiated by SIGUSR1/SIGTERM/SIGUSR2).
194 * Wait for completion before proceeding.
195 */
196#define SHUTDOWN 0x40
197/*
198 * exec() on SIGQUIT. SHUTDOWN actions are started and waited for,
199 * then all processes are killed, then init exec's 1st RESTART action,
200 * replacing itself by it. If no RESTART action specified,
201 * SIGQUIT has no effect.
202 */
203#define RESTART 0x80
204
205
206/* A linked list of init_actions, to be read from inittab */
207struct init_action {
208 struct init_action *next;
209 pid_t pid;
210 uint8_t action_type;
211 char terminal[CONSOLE_NAME_SIZE];
212 char command[1];
213};
214
215static struct init_action *init_action_list = NULL;
216
217static const char *log_console = VC_5;
218
219enum {
220 L_LOG = 0x1,
221 L_CONSOLE = 0x2,
222};
223
224/* Print a message to the specified device.
225 * "where" may be bitwise-or'd from L_LOG | L_CONSOLE
226 * NB: careful, we can be called after vfork!
227 */
228#define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0)
229static void message(int where, const char *fmt, ...)
230 __attribute__ ((format(printf, 2, 3)));
231static void message(int where, const char *fmt, ...)
232{
233 va_list arguments;
234 unsigned l;
235 char msg[128];
236
237 msg[0] = '\r';
238 va_start(arguments, fmt);
239 l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments);
240 if (l > sizeof(msg) - 2)
241 l = sizeof(msg) - 2;
242 va_end(arguments);
243
244#if ENABLE_FEATURE_INIT_SYSLOG
245 msg[l] = '\0';
246 if (where & L_LOG) {
247 /* Log the message to syslogd */
248 openlog(applet_name, 0, LOG_DAEMON);
249 /* don't print "\r" */
250 syslog(LOG_INFO, "%s", msg + 1);
251 closelog();
252 }
253 msg[l++] = '\n';
254 msg[l] = '\0';
255#else
256 {
257 static int log_fd = -1;
258
259 msg[l++] = '\n';
260 msg[l] = '\0';
261 /* Take full control of the log tty, and never close it.
262 * It's mine, all mine! Muhahahaha! */
263 if (log_fd < 0) {
264 if (!log_console) {
265 log_fd = STDERR_FILENO;
266 } else {
267 log_fd = device_open(log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY);
268 if (log_fd < 0) {
269 bb_error_msg("can't log to %s", log_console);
270 where = L_CONSOLE;
271 } else {
272 close_on_exec_on(log_fd);
273 }
274 }
275 }
276 if (where & L_LOG) {
277 full_write(log_fd, msg, l);
278 if (log_fd == STDERR_FILENO)
279 return; /* don't print dup messages */
280 }
281 }
282#endif
283
284 if (where & L_CONSOLE) {
285 /* Send console messages to console so people will see them. */
286 full_write(STDERR_FILENO, msg, l);
287 }
288}
289
290static void console_init(void)
291{
292#ifdef VT_OPENQRY
293 int vtno;
294#endif
295 char *s;
296
297 s = getenv("CONSOLE");
298 if (!s)
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: */
302 if (!s)
303 s = (char*)"/dev/console";
304#endif
305 if (s) {
306 int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY);
307 if (fd >= 0) {
308 dup2(fd, STDIN_FILENO);
309 dup2(fd, STDOUT_FILENO);
310 xmove_fd(fd, STDERR_FILENO);
311 }
312 dbg_message(L_LOG, "console='%s'", s);
313 } else {
314 /* Make sure fd 0,1,2 are not closed
315 * (so that they won't be used by future opens) */
316 bb_sanitize_stdio();
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);
320 }
321
322 s = getenv("TERM");
323#ifdef VT_OPENQRY
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)
331 log_console = NULL;
332 } else
333#endif
334 if (!s)
335 putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE);
336}
337
338/* Set terminal settings to reasonable defaults.
339 * NB: careful, we can be called after vfork! */
340static void set_sane_term(void)
341{
342 struct termios tty;
343
344 tcgetattr(STDIN_FILENO, &tty);
345
346 /* set control chars */
347 tty.c_cc[VINTR] = 3; /* C-c */
348 tty.c_cc[VQUIT] = 28; /* C-\ */
349 tty.c_cc[VERASE] = 127; /* C-? */
350 tty.c_cc[VKILL] = 21; /* C-u */
351 tty.c_cc[VEOF] = 4; /* C-d */
352 tty.c_cc[VSTART] = 17; /* C-q */
353 tty.c_cc[VSTOP] = 19; /* C-s */
354 tty.c_cc[VSUSP] = 26; /* C-z */
355
356#ifdef __linux__
357 /* use line discipline 0 */
358 tty.c_line = 0;
359#endif
360
361 /* Make it be sane */
362#ifndef CRTSCTS
363# define CRTSCTS 0
364#endif
365 /* added CRTSCTS to fix Debian bug 528560 */
366 tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS;
367 tty.c_cflag |= CREAD | HUPCL | CLOCAL;
368
369 /* input modes */
370 tty.c_iflag = ICRNL | IXON | IXOFF;
371
372 /* output modes */
373 tty.c_oflag = OPOST | ONLCR;
374
375 /* local modes */
376 tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN;
377
378 tcsetattr_stdin_TCSANOW(&tty);
379}
380
381/* Open the new terminal device.
382 * NB: careful, we can be called after vfork! */
383static int open_stdio_to_tty(const char* tty_name)
384{
385 /* empty tty_name means "use init's tty", else... */
386 if (tty_name[0]) {
387 int fd;
388
389 close(STDIN_FILENO);
390 /* fd can be only < 0 or 0: */
391 fd = device_open(tty_name, O_RDWR);
392 if (fd) {
393 message(L_LOG | L_CONSOLE, "can't open %s: %s",
394 tty_name, strerror(errno));
395 return 0; /* failure */
396 }
397 dup2(STDIN_FILENO, STDOUT_FILENO);
398 dup2(STDIN_FILENO, STDERR_FILENO);
399 }
400 set_sane_term();
401 return 1; /* success */
402}
403
404static void reset_sighandlers_and_unblock_sigs(void)
405{
406 bb_signals(0
407 + (1 << SIGUSR1)
408 + (1 << SIGUSR2)
409 + (1 << SIGTERM)
410 + (1 << SIGQUIT)
411 + (1 << SIGINT)
412 + (1 << SIGHUP)
413 + (1 << SIGTSTP)
414 + (1 << SIGSTOP)
415 , SIG_DFL);
416 sigprocmask_allsigs(SIG_UNBLOCK);
417}
418
419/* Wrapper around exec:
420 * Takes string.
421 * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'.
422 * Otherwise splits words on whitespace, deals with leading dash,
423 * and uses plain exec().
424 * NB: careful, we can be called after vfork!
425 */
426static void init_exec(const char *command)
427{
428 /* +8 allows to write VLA sizes below more efficiently: */
429 unsigned command_size = strlen(command) + 8;
430 /* strlen(command) + strlen("exec ")+1: */
431 char buf[command_size];
432 /* strlen(command) / 2 + 4: */
433 char *cmd[command_size / 2];
434 int dash;
435
436 dash = (command[0] == '-' /* maybe? && command[1] == '/' */);
437 command += dash;
438
439 /* See if any special /bin/sh requiring characters are present */
440 if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) {
441 sprintf(buf, "exec %s", command); /* excluding "-" */
442 /* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */
443 cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash);
444 cmd[1] = (char*)"-c";
445 cmd[2] = buf;
446 cmd[3] = NULL;
447 command = LIBBB_DEFAULT_LOGIN_SHELL + 1;
448 } else {
449 /* Convert command (char*) into cmd (char**, one word per string) */
450 char *word, *next;
451 int i = 0;
452 next = strcpy(buf, command - dash); /* command including "-" */
453 command = next + dash;
454 while ((word = strsep(&next, " \t")) != NULL) {
455 if (*word != '\0') { /* not two spaces/tabs together? */
456 cmd[i] = word;
457 i++;
458 }
459 }
460 cmd[i] = NULL;
461 }
462 /* If we saw leading "-", it is interactive shell.
463 * Try harder to give it a controlling tty.
464 */
465 if (ENABLE_FEATURE_INIT_SCTTY && dash) {
466 /* _Attempt_ to make stdin a controlling tty. */
467 ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/);
468 }
469 /* Here command never contains the dash, cmd[0] might */
470 BB_EXECVP(command, cmd);
471 message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno));
472 /* returns if execvp fails */
473}
474
475/* Used only by run_actions */
476static pid_t run(const struct init_action *a)
477{
478 pid_t pid;
479
480 /* Careful: don't be affected by a signal in vforked child */
481 sigprocmask_allsigs(SIG_BLOCK);
482 if (BB_MMU && (a->action_type & ASKFIRST))
483 pid = fork();
484 else
485 pid = vfork();
486 if (pid < 0)
487 message(L_LOG | L_CONSOLE, "can't fork");
488 if (pid) {
489 sigprocmask_allsigs(SIG_UNBLOCK);
490 return pid; /* Parent or error */
491 }
492
493 /* Child */
494
495 /* Reset signal handlers that were set by the parent process */
496 reset_sighandlers_and_unblock_sigs();
497
498 /* Create a new session and make ourself the process group leader */
499 setsid();
500
501 /* Open the new terminal device */
502 if (!open_stdio_to_tty(a->terminal))
503 _exit(EXIT_FAILURE);
504
505 /* NB: on NOMMU we can't wait for input in child, so
506 * "askfirst" will work the same as "respawn". */
507 if (BB_MMU && (a->action_type & ASKFIRST)) {
508 static const char press_enter[] ALIGN1 =
509#ifdef CUSTOMIZED_BANNER
510#include CUSTOMIZED_BANNER
511#endif
512 "\nPlease press Enter to activate this console. ";
513 char c;
514 /*
515 * Save memory by not exec-ing anything large (like a shell)
516 * before the user wants it. This is critical if swap is not
517 * enabled and the system has low memory. Generally this will
518 * be run on the second virtual console, and the first will
519 * be allowed to start a shell or whatever an init script
520 * specifies.
521 */
522 dbg_message(L_LOG, "waiting for enter to start '%s'"
523 "(pid %d, tty '%s')\n",
524 a->command, getpid(), a->terminal);
525 full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1);
526 while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n')
527 continue;
528 }
529
530 /*
531 * When a file named /.init_enable_core exists, setrlimit is called
532 * before processes are spawned to set core file size as unlimited.
533 * This is for debugging only. Don't use this is production, unless
534 * you want core dumps lying about....
535 */
536 if (ENABLE_FEATURE_INIT_COREDUMPS) {
537 if (access("/.init_enable_core", F_OK) == 0) {
538 struct rlimit limit;
539 limit.rlim_cur = RLIM_INFINITY;
540 limit.rlim_max = RLIM_INFINITY;
541 setrlimit(RLIMIT_CORE, &limit);
542 }
543 }
544
545 /* Log the process name and args */
546 message(L_LOG, "starting pid %d, tty '%s': '%s'",
547 getpid(), a->terminal, a->command);
548
549 /* Now run it. The new program will take over this PID,
550 * so nothing further in init.c should be run. */
551 init_exec(a->command);
552 /* We're still here? Some error happened. */
553 _exit(-1);
554}
555
556static struct init_action *mark_terminated(pid_t pid)
557{
558 struct init_action *a;
559
560 if (pid > 0) {
561 update_utmp_DEAD_PROCESS(pid);
562 for (a = init_action_list; a; a = a->next) {
563 if (a->pid == pid) {
564 a->pid = 0;
565 return a;
566 }
567 }
568 }
569 return NULL;
570}
571
572static void waitfor(pid_t pid)
573{
574 /* waitfor(run(x)): protect against failed fork inside run() */
575 if (pid <= 0)
576 return;
577
578 /* Wait for any child (prevent zombies from exiting orphaned processes)
579 * but exit the loop only when specified one has exited. */
580 while (1) {
581 pid_t wpid = wait(NULL);
582 mark_terminated(wpid);
583 /* Unsafe. SIGTSTP handler might have wait'ed it already */
584 /*if (wpid == pid) break;*/
585 /* More reliable: */
586 if (kill(pid, 0))
587 break;
588 }
589}
590
591/* Run all commands of a particular type */
592static void run_actions(int action_type)
593{
594 struct init_action *a;
595
596 for (a = init_action_list; a; a = a->next) {
597 if (!(a->action_type & action_type))
598 continue;
599
600 if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) {
601 pid_t pid = run(a);
602 if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN))
603 waitfor(pid);
604 }
605 if (a->action_type & (RESPAWN | ASKFIRST)) {
606 /* Only run stuff with pid == 0. If pid != 0,
607 * it is already running
608 */
609 if (a->pid == 0)
610 a->pid = run(a);
611 }
612 }
613}
614
615static void new_init_action(uint8_t action_type, const char *command, const char *cons)
616{
617 struct init_action *a, **nextp;
618
619 /* Scenario:
620 * old inittab:
621 * ::shutdown:umount -a -r
622 * ::shutdown:swapoff -a
623 * new inittab:
624 * ::shutdown:swapoff -a
625 * ::shutdown:umount -a -r
626 * On reload, we must ensure entries end up in correct order.
627 * To achieve that, if we find a matching entry, we move it
628 * to the end.
629 */
630 nextp = &init_action_list;
631 while ((a = *nextp) != NULL) {
632 /* Don't enter action if it's already in the list.
633 * This prevents losing running RESPAWNs.
634 */
635 if (strcmp(a->command, command) == 0
636 && strcmp(a->terminal, cons) == 0
637 ) {
638 /* Remove from list */
639 *nextp = a->next;
640 /* Find the end of the list */
641 while (*nextp != NULL)
642 nextp = &(*nextp)->next;
643 a->next = NULL;
644 goto append;
645 }
646 nextp = &a->next;
647 }
648
649 a = xzalloc(sizeof(*a) + strlen(command));
650
651 /* Append to the end of the list */
652 append:
653 *nextp = a;
654 a->action_type = action_type;
655 strcpy(a->command, command);
656 safe_strncpy(a->terminal, cons, sizeof(a->terminal));
657 dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%x tty='%s'\n",
658 a->command, a->action_type, a->terminal);
659}
660
661/* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
662 * then parse_inittab() simply adds in some default
663 * actions (i.e., runs INIT_SCRIPT and then starts a pair
664 * of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB
665 * _is_ defined, but /etc/inittab is missing, this
666 * results in the same set of default behaviors.
667 */
668static void parse_inittab(void)
669{
670#if ENABLE_FEATURE_USE_INITTAB
671 char *token[4];
672 parser_t *parser = config_open2("/etc/inittab", fopen_for_read);
673
674 if (parser == NULL)
675#endif
676 {
677 /* No inittab file - set up some default behavior */
678 /* Sysinit */
679 new_init_action(SYSINIT, INIT_SCRIPT, "");
680 /* Askfirst shell on tty1-4 */
681 new_init_action(ASKFIRST, bb_default_login_shell, "");
682//TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users
683 new_init_action(ASKFIRST, bb_default_login_shell, VC_2);
684 new_init_action(ASKFIRST, bb_default_login_shell, VC_3);
685 new_init_action(ASKFIRST, bb_default_login_shell, VC_4);
686 /* Reboot on Ctrl-Alt-Del */
687 new_init_action(CTRLALTDEL, "reboot", "");
688 /* Umount all filesystems on halt/reboot */
689 new_init_action(SHUTDOWN, "umount -a -r", "");
690 /* Swapoff on halt/reboot */
691 new_init_action(SHUTDOWN, "swapoff -a", "");
692 /* Restart init when a QUIT is received */
693 new_init_action(RESTART, "init", "");
694 return;
695 }
696
697#if ENABLE_FEATURE_USE_INITTAB
698 /* optional_tty:ignored_runlevel:action:command
699 * Delims are not to be collapsed and need exactly 4 tokens
700 */
701 while (config_read(parser, token, 4, 0, "#:",
702 PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) {
703 /* order must correspond to SYSINIT..RESTART constants */
704 static const char actions[] ALIGN1 =
705 "sysinit\0""wait\0""once\0""respawn\0""askfirst\0"
706 "ctrlaltdel\0""shutdown\0""restart\0";
707 int action;
708 char *tty = token[0];
709
710 if (!token[3]) /* less than 4 tokens */
711 goto bad_entry;
712 action = index_in_strings(actions, token[2]);
713 if (action < 0 || !token[3][0]) /* token[3]: command */
714 goto bad_entry;
715 /* turn .*TTY -> /dev/TTY */
716 if (tty[0]) {
717 tty = concat_path_file("/dev/", skip_dev_pfx(tty));
718 }
719 new_init_action(1 << action, token[3], tty);
720 if (tty[0])
721 free(tty);
722 continue;
723 bad_entry:
724 message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d",
725 parser->lineno);
726 }
727 config_close(parser);
728#endif
729}
730
731static void pause_and_low_level_reboot(unsigned magic) NORETURN;
732static void pause_and_low_level_reboot(unsigned magic)
733{
734 pid_t pid;
735
736 /* Allow time for last message to reach serial console, etc */
737 sleep(1);
738
739 /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS)
740 * in linux/kernel/sys.c, which can cause the machine to panic when
741 * the init process exits... */
742 pid = vfork();
743 if (pid == 0) { /* child */
744 reboot(magic);
745 _exit(EXIT_SUCCESS);
746 }
747 while (1)
748 sleep(1);
749}
750
751static void run_shutdown_and_kill_processes(void)
752{
753 /* Run everything to be run at "shutdown". This is done _prior_
754 * to killing everything, in case people wish to use scripts to
755 * shut things down gracefully... */
756 run_actions(SHUTDOWN);
757
758 message(L_CONSOLE | L_LOG, "The system is going down NOW!");
759
760 /* Send signals to every process _except_ pid 1 */
761 kill(-1, SIGTERM);
762 message(L_CONSOLE | L_LOG, "Sent SIG%s to all processes", "TERM");
763 sync();
764 sleep(1);
765
766 kill(-1, SIGKILL);
767 message(L_CONSOLE, "Sent SIG%s to all processes", "KILL");
768 sync();
769 /*sleep(1); - callers take care about making a pause */
770}
771
772/* Signal handling by init:
773 *
774 * For process with PID==1, on entry kernel sets all signals to SIG_DFL
775 * and unmasks all signals. However, for process with PID==1,
776 * default action (SIG_DFL) on any signal is to ignore it,
777 * even for special signals SIGKILL and SIGCONT.
778 * Also, any signal can be caught or blocked.
779 * (but SIGSTOP is still handled specially, at least in 2.6.20)
780 *
781 * We install two kinds of handlers, "immediate" and "delayed".
782 *
783 * Immediate handlers execute at any time, even while, say, sysinit
784 * is running.
785 *
786 * Delayed handlers just set a flag variable. The variable is checked
787 * in the main loop and acted upon.
788 *
789 * halt/poweroff/reboot and restart have immediate handlers.
790 * They only traverse linked list of struct action's, never modify it,
791 * this should be safe to do even in signal handler. Also they
792 * never return.
793 *
794 * SIGSTOP and SIGTSTP have immediate handlers. They just wait
795 * for SIGCONT to happen.
796 *
797 * SIGHUP has a delayed handler, because modifying linked list
798 * of struct action's from a signal handler while it is manipulated
799 * by the program may be disastrous.
800 *
801 * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing
802 * it to happen even somewhere inside "sysinit" would be a bit awkward.
803 *
804 * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide
805 * and only one will be remembered and acted upon.
806 */
807
808/* The SIGPWR/SIGUSR[12]/SIGTERM handler */
809static void halt_reboot_pwoff(int sig) NORETURN;
810static void halt_reboot_pwoff(int sig)
811{
812 const char *m;
813 unsigned rb;
814
815 /* We may call run() and it unmasks signals,
816 * including the one masked inside this signal handler.
817 * Testcase which would start multiple reboot scripts:
818 * while true; do reboot; done
819 * Preventing it:
820 */
821 reset_sighandlers_and_unblock_sigs();
822
823 run_shutdown_and_kill_processes();
824
825 m = "halt";
826 rb = RB_HALT_SYSTEM;
827 if (sig == SIGTERM) {
828 m = "reboot";
829 rb = RB_AUTOBOOT;
830 } else if (sig == SIGUSR2) {
831 m = "poweroff";
832 rb = RB_POWER_OFF;
833 }
834 message(L_CONSOLE, "Requesting system %s", m);
835 pause_and_low_level_reboot(rb);
836 /* not reached */
837}
838
839/* Handler for QUIT - exec "restart" action,
840 * else (no such action defined) do nothing */
841static void exec_restart_action(void)
842{
843 struct init_action *a;
844
845 for (a = init_action_list; a; a = a->next) {
846 if (!(a->action_type & RESTART))
847 continue;
848
849 /* Starting from here, we won't return.
850 * Thus don't need to worry about preserving errno
851 * and such.
852 */
853
854 reset_sighandlers_and_unblock_sigs();
855
856 run_shutdown_and_kill_processes();
857
858#ifdef RB_ENABLE_CAD
859 /* Allow Ctrl-Alt-Del to reboot the system.
860 * This is how kernel sets it up for init, we follow suit.
861 */
862 reboot(RB_ENABLE_CAD); /* misnomer */
863#endif
864
865 if (open_stdio_to_tty(a->terminal)) {
866 dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command);
867 /* Theoretically should be safe.
868 * But in practice, kernel bugs may leave
869 * unkillable processes, and wait() may block forever.
870 * Oh well. Hoping "new" init won't be too surprised
871 * by having children it didn't create.
872 */
873 //while (wait(NULL) > 0)
874 // continue;
875 init_exec(a->command);
876 }
877 /* Open or exec failed */
878 pause_and_low_level_reboot(RB_HALT_SYSTEM);
879 /* not reached */
880 }
881}
882
883/* The SIGSTOP/SIGTSTP handler
884 * NB: inside it, all signals except SIGCONT are masked
885 * via appropriate setup in sigaction().
886 */
887static void stop_handler(int sig UNUSED_PARAM)
888{
889 smallint saved_bb_got_signal;
890 int saved_errno;
891
892 saved_bb_got_signal = bb_got_signal;
893 saved_errno = errno;
894 signal(SIGCONT, record_signo);
895
896 while (1) {
897 pid_t wpid;
898
899 if (bb_got_signal == SIGCONT)
900 break;
901 /* NB: this can accidentally wait() for a process
902 * which we waitfor() elsewhere! waitfor() must have
903 * code which is resilient against this.
904 */
905 wpid = wait_any_nohang(NULL);
906 mark_terminated(wpid);
907 sleep(1);
908 }
909
910 signal(SIGCONT, SIG_DFL);
911 errno = saved_errno;
912 bb_got_signal = saved_bb_got_signal;
913}
914
915#if ENABLE_FEATURE_USE_INITTAB
916static void reload_inittab(void)
917{
918 struct init_action *a, **nextp;
919
920 message(L_LOG, "reloading /etc/inittab");
921
922 /* Disable old entries */
923 for (a = init_action_list; a; a = a->next)
924 a->action_type = 0;
925
926 /* Append new entries, or modify existing entries
927 * (incl. setting a->action_type) if cmd and device name
928 * match new ones. End result: only entries with
929 * a->action_type == 0 are stale.
930 */
931 parse_inittab();
932
933#if ENABLE_FEATURE_KILL_REMOVED
934 /* Kill stale entries */
935 /* Be nice and send SIGTERM first */
936 for (a = init_action_list; a; a = a->next)
937 if (a->action_type == 0 && a->pid != 0)
938 kill(a->pid, SIGTERM);
939 if (CONFIG_FEATURE_KILL_DELAY) {
940 /* NB: parent will wait in NOMMU case */
941 if ((BB_MMU ? fork() : vfork()) == 0) { /* child */
942 sleep(CONFIG_FEATURE_KILL_DELAY);
943 for (a = init_action_list; a; a = a->next)
944 if (a->action_type == 0 && a->pid != 0)
945 kill(a->pid, SIGKILL);
946 _exit(EXIT_SUCCESS);
947 }
948 }
949#endif
950
951 /* Remove stale entries and SYSINIT entries.
952 * We never rerun SYSINIT entries anyway,
953 * removing them too saves a few bytes
954 */
955 nextp = &init_action_list;
956 while ((a = *nextp) != NULL) {
957 /*
958 * Why pid == 0 check?
959 * Process can be removed from inittab and added *later*.
960 * If we delete its entry but process still runs,
961 * duplicate is spawned when the entry is re-added.
962 */
963 if ((a->action_type & ~SYSINIT) == 0 && a->pid == 0) {
964 *nextp = a->next;
965 free(a);
966 } else {
967 nextp = &a->next;
968 }
969 }
970
971 /* Not needed: */
972 /* run_actions(RESPAWN | ASKFIRST); */
973 /* - we return to main loop, which does this automagically */
974}
975#endif
976
977static int check_delayed_sigs(void)
978{
979 int sigs_seen = 0;
980
981 while (1) {
982 smallint sig = bb_got_signal;
983
984 if (!sig)
985 return sigs_seen;
986 bb_got_signal = 0;
987 sigs_seen = 1;
988#if ENABLE_FEATURE_USE_INITTAB
989 if (sig == SIGHUP)
990 reload_inittab();
991#endif
992 if (sig == SIGINT)
993 run_actions(CTRLALTDEL);
994 if (sig == SIGQUIT) {
995 exec_restart_action();
996 /* returns only if no restart action defined */
997 }
998 if ((1 << sig) & (0
999#ifdef SIGPWR
1000 + (1 << SIGPWR)
1001#endif
1002 + (1 << SIGUSR1)
1003 + (1 << SIGUSR2)
1004 + (1 << SIGTERM)
1005 )) {
1006 halt_reboot_pwoff(sig);
1007 }
1008 }
1009}
1010
1011#if DEBUG_SEGV_HANDLER
1012static
1013void handle_sigsegv(int sig, siginfo_t *info, void *ucontext)
1014{
1015 long ip;
1016 ucontext_t *uc;
1017
1018 uc = ucontext;
1019 ip = uc->uc_mcontext.gregs[REG_EIP];
1020 fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n",
1021 sig,
1022 /* this is void*, but using %p would print "(null)"
1023 * even for ptrs which are not exactly 0, but, say, 0x123:
1024 */
1025 (long)info->si_addr,
1026 ip);
1027 {
1028 /* glibc extension */
1029 void *array[50];
1030 int size;
1031 size = backtrace(array, 50);
1032 backtrace_symbols_fd(array, size, 2);
1033 }
1034 for (;;) sleep(9999);
1035}
1036#endif
1037
1038static void sleep_much(void)
1039{
1040 sleep(30 * 24*60*60);
1041}
1042
1043int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
1044int init_main(int argc UNUSED_PARAM, char **argv)
1045{
1046 if (argv[1] && strcmp(argv[1], "-q") == 0) {
1047 return kill(1, SIGHUP);
1048 }
1049
1050#if DEBUG_SEGV_HANDLER
1051 {
1052 struct sigaction sa;
1053 memset(&sa, 0, sizeof(sa));
1054 sa.sa_sigaction = handle_sigsegv;
1055 sa.sa_flags = SA_SIGINFO;
1056 sigaction(SIGSEGV, &sa, NULL);
1057 sigaction(SIGILL, &sa, NULL);
1058 sigaction(SIGFPE, &sa, NULL);
1059 sigaction(SIGBUS, &sa, NULL);
1060 }
1061#endif
1062
1063 if (!DEBUG_INIT) {
1064 /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */
1065 if (getpid() != 1
1066 && (!ENABLE_LINUXRC || applet_name[0] != 'l') /* not linuxrc? */
1067 ) {
1068 bb_error_msg_and_die("must be run as PID 1");
1069 }
1070#ifdef RB_DISABLE_CAD
1071 /* Turn off rebooting via CTL-ALT-DEL - we get a
1072 * SIGINT on CAD so we can shut things down gracefully... */
1073 reboot(RB_DISABLE_CAD); /* misnomer */
1074#endif
1075 }
1076
1077 /* If, say, xmalloc would ever die, we don't want to oops kernel
1078 * by exiting.
1079 * NB: we set die_func *after* PID 1 check and bb_show_usage.
1080 * Otherwise, for example, "init u" ("please rexec yourself"
1081 * command for sysvinit) will show help text (which isn't too bad),
1082 * *and sleep forever* (which is bad!)
1083 */
1084 die_func = sleep_much;
1085
1086 /* Figure out where the default console should be */
1087 console_init();
1088 set_sane_term();
1089 xchdir("/");
1090 setsid();
1091
1092 /* Make sure environs is set to something sane */
1093 putenv((char *) "HOME=/");
1094 putenv((char *) bb_PATH_root_path);
1095 putenv((char *) "SHELL=/bin/sh");
1096 putenv((char *) "USER=root"); /* needed? why? */
1097
1098 if (argv[1])
1099 xsetenv("RUNLEVEL", argv[1]);
1100
1101#if !ENABLE_FEATURE_EXTRA_QUIET
1102 /* Hello world */
1103 message(L_CONSOLE | L_LOG, "init started: %s", bb_banner);
1104#endif
1105
1106#if 0
1107/* It's 2013, does anyone really still depend on this? */
1108/* If you do, consider adding swapon to sysinit actions then! */
1109/* struct sysinfo is linux-specific */
1110# ifdef __linux__
1111 /* Make sure there is enough memory to do something useful. */
1112 /*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ {
1113 struct sysinfo info;
1114
1115 if (sysinfo(&info) == 0
1116 && (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024
1117 ) {
1118 message(L_CONSOLE, "Low memory, forcing swapon");
1119 /* swapon -a requires /proc typically */
1120 new_init_action(SYSINIT, "mount -t proc proc /proc", "");
1121 /* Try to turn on swap */
1122 new_init_action(SYSINIT, "swapon -a", "");
1123 run_actions(SYSINIT); /* wait and removing */
1124 }
1125 }
1126# endif
1127#endif
1128
1129 /* Check if we are supposed to be in single user mode */
1130 if (argv[1]
1131 && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1'))
1132 ) {
1133 /* ??? shouldn't we set RUNLEVEL="b" here? */
1134 /* Start a shell on console */
1135 new_init_action(RESPAWN, bb_default_login_shell, "");
1136 } else {
1137 /* Not in single user mode - see what inittab says */
1138
1139 /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined,
1140 * then parse_inittab() simply adds in some default
1141 * actions (i.e., INIT_SCRIPT and a pair
1142 * of "askfirst" shells) */
1143 parse_inittab();
1144 }
1145
1146/*#if ENABLE_SELINUX
1147 if (getenv("SELINUX_INIT") == NULL) {
1148 int enforce = 0;
1149
1150 putenv((char*)"SELINUX_INIT=YES");
1151 if (selinux_init_load_policy(&enforce) == 0) {
1152 BB_EXECVP(argv[0], argv);
1153 } else if (enforce > 0) {
1154 message(L_CONSOLE, "can't load SELinux Policy. "
1155 "Machine is in enforcing mode. Halting now.");
1156 return EXIT_FAILURE;
1157 }
1158 }
1159#endif*/
1160
1161 if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE) {
1162 /* Make the command line just say "init" - that's all, nothing else */
1163 strncpy(argv[0], "init", strlen(argv[0]));
1164 /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */
1165 while (*++argv)
1166 nuke_str(*argv);
1167 }
1168
1169 /* Set up signal handlers */
1170 if (!DEBUG_INIT) {
1171 struct sigaction sa;
1172
1173 /* Stop handler must allow only SIGCONT inside itself */
1174 memset(&sa, 0, sizeof(sa));
1175 sigfillset(&sa.sa_mask);
1176 sigdelset(&sa.sa_mask, SIGCONT);
1177 sa.sa_handler = stop_handler;
1178 /* NB: sa_flags doesn't have SA_RESTART.
1179 * It must be able to interrupt wait().
1180 */
1181 sigaction_set(SIGTSTP, &sa); /* pause */
1182 /* Does not work as intended, at least in 2.6.20.
1183 * SIGSTOP is simply ignored by init:
1184 */
1185 sigaction_set(SIGSTOP, &sa); /* pause */
1186
1187 /* These signals must interrupt wait(),
1188 * setting handler without SA_RESTART flag.
1189 */
1190 bb_signals_recursive_norestart(0
1191 + (1 << SIGINT) /* Ctrl-Alt-Del */
1192 + (1 << SIGQUIT) /* re-exec another init */
1193#ifdef SIGPWR
1194 + (1 << SIGPWR) /* halt */
1195#endif
1196 + (1 << SIGUSR1) /* halt */
1197 + (1 << SIGTERM) /* reboot */
1198 + (1 << SIGUSR2) /* poweroff */
1199#if ENABLE_FEATURE_USE_INITTAB
1200 + (1 << SIGHUP) /* reread /etc/inittab */
1201#endif
1202 , record_signo);
1203 }
1204
1205 /* Now run everything that needs to be run */
1206 /* First run the sysinit command */
1207 run_actions(SYSINIT);
1208 check_delayed_sigs();
1209 /* Next run anything that wants to block */
1210 run_actions(WAIT);
1211 check_delayed_sigs();
1212 /* Next run anything to be run only once */
1213 run_actions(ONCE);
1214
1215 /* Now run the looping stuff for the rest of forever.
1216 */
1217 while (1) {
1218 int maybe_WNOHANG;
1219
1220 maybe_WNOHANG = check_delayed_sigs();
1221
1222 /* (Re)run the respawn/askfirst stuff */
1223 run_actions(RESPAWN | ASKFIRST);
1224 maybe_WNOHANG |= check_delayed_sigs();
1225
1226 /* Don't consume all CPU time - sleep a bit */
1227 sleep(1);
1228 maybe_WNOHANG |= check_delayed_sigs();
1229
1230 /* Wait for any child process(es) to exit.
1231 *
1232 * If check_delayed_sigs above reported that a signal
1233 * was caught, wait will be nonblocking. This ensures
1234 * that if SIGHUP has reloaded inittab, respawn and askfirst
1235 * actions will not be delayed until next child death.
1236 */
1237 if (maybe_WNOHANG)
1238 maybe_WNOHANG = WNOHANG;
1239 while (1) {
1240 pid_t wpid;
1241 struct init_action *a;
1242
1243 /* If signals happen _in_ the wait, they interrupt it,
1244 * bb_signals_recursive_norestart set them up that way
1245 */
1246 wpid = waitpid(-1, NULL, maybe_WNOHANG);
1247 if (wpid <= 0)
1248 break;
1249
1250 a = mark_terminated(wpid);
1251 if (a) {
1252 message(L_LOG, "process '%s' (pid %d) exited. "
1253 "Scheduling for restart.",
1254 a->command, wpid);
1255 }
1256 /* See if anyone else is waiting to be reaped */
1257 maybe_WNOHANG = WNOHANG;
1258 }
1259 } /* while (1) */
1260}
1261
1262//usage:#define linuxrc_trivial_usage NOUSAGE_STR
1263//usage:#define linuxrc_full_usage ""
1264
1265//usage:#define init_trivial_usage
1266//usage: ""
1267//usage:#define init_full_usage "\n\n"
1268//usage: "Init is the first process started during boot. It never exits."
1269//usage: IF_FEATURE_USE_INITTAB(
1270//usage: "\n""It (re)spawns children according to /etc/inittab."
1271//usage: )
1272//usage: IF_NOT_FEATURE_USE_INITTAB(
1273//usage: "\n""This version of init doesn't use /etc/inittab,"
1274//usage: "\n""has fixed set of processed to run."
1275//usage: )
1276//usage:
1277//usage:#define init_notes_usage
1278//usage: "This version of init is designed to be run only by the kernel.\n"
1279//usage: "\n"
1280//usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n"
1281//usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n"
1282//usage: "runlevels, use sysvinit.\n"
1283//usage: "\n"
1284//usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n"
1285//usage: "it has the following default behavior:\n"
1286//usage: "\n"
1287//usage: " ::sysinit:/etc/init.d/rcS\n"
1288//usage: " ::askfirst:/bin/sh\n"
1289//usage: " ::ctrlaltdel:/sbin/reboot\n"
1290//usage: " ::shutdown:/sbin/swapoff -a\n"
1291//usage: " ::shutdown:/bin/umount -a -r\n"
1292//usage: " ::restart:/sbin/init\n"
1293//usage: " tty2::askfirst:/bin/sh\n"
1294//usage: " tty3::askfirst:/bin/sh\n"
1295//usage: " tty4::askfirst:/bin/sh\n"
1296//usage: "\n"
1297//usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n"
1298//usage: "\n"
1299//usage: " <id>:<runlevels>:<action>:<process>\n"
1300//usage: "\n"
1301//usage: " <id>:\n"
1302//usage: "\n"
1303//usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n"
1304//usage: " The id field is used by BusyBox init to specify the controlling tty for\n"
1305//usage: " the specified process to run on. The contents of this field are\n"
1306//usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n"
1307//usage: " be unique, although if it isn't you may have strange results. If this\n"
1308//usage: " field is left blank, then the init's stdin/out will be used.\n"
1309//usage: "\n"
1310//usage: " <runlevels>:\n"
1311//usage: "\n"
1312//usage: " The runlevels field is completely ignored.\n"
1313//usage: "\n"
1314//usage: " <action>:\n"
1315//usage: "\n"
1316//usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n"
1317//usage: " once, restart, ctrlaltdel, and shutdown.\n"
1318//usage: "\n"
1319//usage: " The available actions can be classified into two groups: actions\n"
1320//usage: " that are run only once, and actions that are re-run when the specified\n"
1321//usage: " process exits.\n"
1322//usage: "\n"
1323//usage: " Run only-once actions:\n"
1324//usage: "\n"
1325//usage: " 'sysinit' is the first item run on boot. init waits until all\n"
1326//usage: " sysinit actions are completed before continuing. Following the\n"
1327//usage: " completion of all sysinit actions, all 'wait' actions are run.\n"
1328//usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n"
1329//usage: " the specified task completes. 'once' actions are asynchronous,\n"
1330//usage: " therefore, init does not wait for them to complete. 'restart' is\n"
1331//usage: " the action taken to restart the init process. By default this should\n"
1332//usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n"
1333//usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n"
1334//usage: " actions are run when the system detects that someone on the system\n"
1335//usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n"
1336//usage: " wants to run 'reboot' at this point to cause the system to reboot.\n"
1337//usage: " Finally the 'shutdown' action specifies the actions to taken when\n"
1338//usage: " init is told to reboot. Unmounting filesystems and disabling swap\n"
1339//usage: " is a very good here.\n"
1340//usage: "\n"
1341//usage: " Run repeatedly actions:\n"
1342//usage: "\n"
1343//usage: " 'respawn' actions are run after the 'once' actions. When a process\n"
1344//usage: " started with a 'respawn' action exits, init automatically restarts\n"
1345//usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n"
1346//usage: " respawning out of control. The 'askfirst' actions acts just like\n"
1347//usage: " respawn, except that before running the specified process it\n"
1348//usage: " displays the line \"Please press Enter to activate this console.\"\n"
1349//usage: " and then waits for the user to press enter before starting the\n"
1350//usage: " specified process.\n"
1351//usage: "\n"
1352//usage: " Unrecognized actions (like initdefault) will cause init to emit an\n"
1353//usage: " error message, and then go along with its business. All actions are\n"
1354//usage: " run in the order they appear in /etc/inittab.\n"
1355//usage: "\n"
1356//usage: " <process>:\n"
1357//usage: "\n"
1358//usage: " Specifies the process to be executed and its command line.\n"
1359//usage: "\n"
1360//usage: "Example /etc/inittab file:\n"
1361//usage: "\n"
1362//usage: " # This is run first except when booting in single-user mode\n"
1363//usage: " #\n"
1364//usage: " ::sysinit:/etc/init.d/rcS\n"
1365//usage: " \n"
1366//usage: " # /bin/sh invocations on selected ttys\n"
1367//usage: " #\n"
1368//usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n"
1369//usage: " ::askfirst:-/bin/sh\n"
1370//usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n"
1371//usage: " tty2::askfirst:-/bin/sh\n"
1372//usage: " tty3::askfirst:-/bin/sh\n"
1373//usage: " tty4::askfirst:-/bin/sh\n"
1374//usage: " \n"
1375//usage: " # /sbin/getty invocations for selected ttys\n"
1376//usage: " #\n"
1377//usage: " tty4::respawn:/sbin/getty 38400 tty4\n"
1378//usage: " tty5::respawn:/sbin/getty 38400 tty5\n"
1379//usage: " \n"
1380//usage: " \n"
1381//usage: " # Example of how to put a getty on a serial line (for a terminal)\n"
1382//usage: " #\n"
1383//usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n"
1384//usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n"
1385//usage: " #\n"
1386//usage: " # Example how to put a getty on a modem line\n"
1387//usage: " #::respawn:/sbin/getty 57600 ttyS2\n"
1388//usage: " \n"
1389//usage: " # Stuff to do when restarting the init process\n"
1390//usage: " ::restart:/sbin/init\n"
1391//usage: " \n"
1392//usage: " # Stuff to do before rebooting\n"
1393//usage: " ::ctrlaltdel:/sbin/reboot\n"
1394//usage: " ::shutdown:/bin/umount -a -r\n"
1395//usage: " ::shutdown:/sbin/swapoff -a\n"
1396
generated by cgit at 2024-05-15 03:11:40 (GMT)