| /* vi: set sw=4 ts=4: */ |
| /* |
| * Mini init implementation for busybox |
| * |
| * Copyright (C) 1995, 1996 by Bruce Perens <bruce@pixar.com>. |
| * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org> |
| * Adjusted by so many folks, it's impossible to keep track. |
| * |
| * Licensed under GPLv2 or later, see file LICENSE in this source tree. |
| */ |
| |
| //config:config INIT |
| //config: bool "init" |
| //config: default y |
| //config: select FEATURE_SYSLOG |
| //config: help |
| //config: init is the first program run when the system boots. |
| //config: |
| //config:config LINUXRC |
| //config: bool "linuxrc: support running init from initrd (not initramfs)" |
| //config: default y |
| //config: select FEATURE_SYSLOG |
| //config: help |
| //config: Legacy support for running init under the old-style initrd. Allows |
| //config: the name linuxrc to act as init, and it doesn't assume init is PID 1. |
| //config: |
| //config: This does not apply to initramfs, which runs /init as PID 1 and |
| //config: requires no special support. |
| //config: |
| //config:config FEATURE_USE_INITTAB |
| //config: bool "Support reading an inittab file" |
| //config: default y |
| //config: depends on INIT || LINUXRC |
| //config: help |
| //config: Allow init to read an inittab file when the system boot. |
| //config: |
| //config:config FEATURE_KILL_REMOVED |
| //config: bool "Support killing processes that have been removed from inittab" |
| //config: default n |
| //config: depends on FEATURE_USE_INITTAB |
| //config: help |
| //config: When respawn entries are removed from inittab and a SIGHUP is |
| //config: sent to init, this option will make init kill the processes |
| //config: that have been removed. |
| //config: |
| //config:config FEATURE_KILL_DELAY |
| //config: int "How long to wait between TERM and KILL (0 - send TERM only)" if FEATURE_KILL_REMOVED |
| //config: range 0 1024 |
| //config: default 0 |
| //config: depends on FEATURE_KILL_REMOVED |
| //config: help |
| //config: With nonzero setting, init sends TERM, forks, child waits N |
| //config: seconds, sends KILL and exits. Setting it too high is unwise |
| //config: (child will hang around for too long and could actually kill |
| //config: the wrong process!) |
| //config: |
| //config:config FEATURE_INIT_SCTTY |
| //config: bool "Run commands with leading dash with controlling tty" |
| //config: default y |
| //config: depends on INIT || LINUXRC |
| //config: help |
| //config: If this option is enabled, init will try to give a controlling |
| //config: tty to any command which has leading hyphen (often it's "-/bin/sh"). |
| //config: More precisely, init will do "ioctl(STDIN_FILENO, TIOCSCTTY, 0)". |
| //config: If device attached to STDIN_FILENO can be a ctty but is not yet |
| //config: a ctty for other session, it will become this process' ctty. |
| //config: This is not the traditional init behavour, but is often what you want |
| //config: in an embedded system where the console is only accessed during |
| //config: development or for maintenance. |
| //config: NB: using cttyhack applet may work better. |
| //config: |
| //config:config FEATURE_INIT_SYSLOG |
| //config: bool "Enable init to write to syslog" |
| //config: default y |
| //config: depends on INIT || LINUXRC |
| //config: help |
| //config: If selected, some init messages are sent to syslog. |
| //config: Otherwise, they are sent to VT #5 if linux virtual tty is detected |
| //config: (if not, no separate logging is done). |
| //config: |
| //config:config FEATURE_INIT_QUIET |
| //config: bool "Be quiet on boot (no 'init started:' message)" |
| //config: default y |
| //config: depends on INIT || LINUXRC |
| //config: |
| //config:config FEATURE_INIT_COREDUMPS |
| //config: bool "Support dumping core for child processes (debugging only)" |
| //config: default n # not Y because this is a debug option |
| //config: depends on INIT || LINUXRC |
| //config: help |
| //config: If this option is enabled and the file /.init_enable_core |
| //config: exists, then init will call setrlimit() to allow unlimited |
| //config: core file sizes. If this option is disabled, processes |
| //config: will not generate any core files. |
| //config: |
| //config:config INIT_TERMINAL_TYPE |
| //config: string "Initial terminal type" |
| //config: default "linux" |
| //config: depends on INIT || LINUXRC |
| //config: help |
| //config: This is the initial value set by init for the TERM environment |
| //config: variable. This variable is used by programs which make use of |
| //config: extended terminal capabilities. |
| //config: |
| //config: Note that on Linux, init attempts to detect serial terminal and |
| //config: sets TERM to "vt102" if one is found. |
| //config: |
| //config:config FEATURE_INIT_MODIFY_CMDLINE |
| //config: bool "Clear init's command line" |
| //config: default y |
| //config: depends on INIT || LINUXRC |
| //config: help |
| //config: When launched as PID 1 and after parsing its arguments, init |
| //config: wipes all the arguments but argv[0] and rewrites argv[0] to |
| //config: contain only "init", so that its command line appears solely as |
| //config: "init" in tools such as ps. |
| //config: If this option is set to Y, init will keep its original behavior, |
| //config: otherwise, all the arguments including argv[0] will be preserved, |
| //config: be they parsed or ignored by init. |
| //config: The original command-line used to launch init can then be |
| //config: retrieved in /proc/1/cmdline on Linux, for example. |
| |
| //applet:IF_INIT(APPLET(init, BB_DIR_SBIN, BB_SUID_DROP)) |
| //applet:IF_LINUXRC(APPLET_ODDNAME(linuxrc, init, BB_DIR_ROOT, BB_SUID_DROP, linuxrc)) |
| |
| //kbuild:lib-$(CONFIG_INIT) += init.o |
| //kbuild:lib-$(CONFIG_LINUXRC) += init.o |
| |
| #define DEBUG_SEGV_HANDLER 0 |
| |
| #include "libbb.h" |
| #include <syslog.h> |
| #include <sys/resource.h> |
| #ifdef __linux__ |
| # include <linux/vt.h> |
| # include <sys/sysinfo.h> |
| #endif |
| #include "reboot.h" /* reboot() constants */ |
| |
| #if DEBUG_SEGV_HANDLER |
| # undef _GNU_SOURCE |
| # define _GNU_SOURCE 1 |
| # undef __USE_GNU |
| # define __USE_GNU 1 |
| # include <execinfo.h> |
| # include <sys/ucontext.h> |
| #endif |
| |
| /* Used only for sanitizing purposes in set_sane_term() below. On systems where |
| * the baud rate is stored in a separate field, we can safely disable them. */ |
| #ifndef CBAUD |
| # define CBAUD 0 |
| # define CBAUDEX 0 |
| #endif |
| |
| /* Was a CONFIG_xxx option. A lot of people were building |
| * not fully functional init by switching it on! */ |
| #define DEBUG_INIT 0 |
| |
| #define CONSOLE_NAME_SIZE 32 |
| |
| /* Default sysinit script. */ |
| #ifndef INIT_SCRIPT |
| # define INIT_SCRIPT "/etc/init.d/rcS" |
| #endif |
| |
| /* Each type of actions can appear many times. They will be |
| * handled in order. RESTART is an exception, only 1st is used. |
| */ |
| /* Start these actions first and wait for completion */ |
| #define SYSINIT 0x01 |
| /* Start these after SYSINIT and wait for completion */ |
| #define WAIT 0x02 |
| /* Start these after WAIT and *dont* wait for completion */ |
| #define ONCE 0x04 |
| /* |
| * NB: while SYSINIT/WAIT/ONCE are being processed, |
| * SIGHUP ("reread /etc/inittab") will be processed only after |
| * each group of actions. If new inittab adds, say, a SYSINIT action, |
| * it will not be run, since init is already "past SYSINIT stage". |
| */ |
| /* Start these after ONCE are started, restart on exit */ |
| #define RESPAWN 0x08 |
| /* Like RESPAWN, but wait for <Enter> to be pressed on tty */ |
| #define ASKFIRST 0x10 |
| /* |
| * Start these on SIGINT, and wait for completion. |
| * Then go back to respawning RESPAWN and ASKFIRST actions. |
| * NB: kernel sends SIGINT to us if Ctrl-Alt-Del was pressed. |
| */ |
| #define CTRLALTDEL 0x20 |
| /* |
| * Start these before killing all processes in preparation for |
| * running RESTART actions or doing low-level halt/reboot/poweroff |
| * (initiated by SIGUSR1/SIGTERM/SIGUSR2). |
| * Wait for completion before proceeding. |
| */ |
| #define SHUTDOWN 0x40 |
| /* |
| * exec() on SIGQUIT. SHUTDOWN actions are started and waited for, |
| * then all processes are killed, then init exec's 1st RESTART action, |
| * replacing itself by it. If no RESTART action specified, |
| * SIGQUIT has no effect. |
| */ |
| #define RESTART 0x80 |
| |
| |
| /* A linked list of init_actions, to be read from inittab */ |
| struct init_action { |
| struct init_action *next; |
| pid_t pid; |
| uint8_t action_type; |
| char terminal[CONSOLE_NAME_SIZE]; |
| char command[1]; |
| }; |
| |
| static struct init_action *init_action_list = NULL; |
| |
| #if !ENABLE_FEATURE_INIT_SYSLOG |
| static const char *log_console = VC_5; |
| #endif |
| |
| enum { |
| L_LOG = 0x1, |
| L_CONSOLE = 0x2, |
| }; |
| |
| /* Print a message to the specified device. |
| * "where" may be bitwise-or'd from L_LOG | L_CONSOLE |
| * NB: careful, we can be called after vfork! |
| */ |
| #define dbg_message(...) do { if (DEBUG_INIT) message(__VA_ARGS__); } while (0) |
| static void message(int where, const char *fmt, ...) |
| __attribute__ ((format(printf, 2, 3))); |
| static void message(int where, const char *fmt, ...) |
| { |
| va_list arguments; |
| unsigned l; |
| char msg[128]; |
| |
| msg[0] = '\r'; |
| va_start(arguments, fmt); |
| l = 1 + vsnprintf(msg + 1, sizeof(msg) - 2, fmt, arguments); |
| if (l > sizeof(msg) - 2) |
| l = sizeof(msg) - 2; |
| va_end(arguments); |
| |
| #if ENABLE_FEATURE_INIT_SYSLOG |
| msg[l] = '\0'; |
| if (where & L_LOG) { |
| /* Log the message to syslogd */ |
| openlog(applet_name, 0, LOG_DAEMON); |
| /* don't print "\r" */ |
| syslog(LOG_INFO, "%s", msg + 1); |
| closelog(); |
| } |
| msg[l++] = '\n'; |
| msg[l] = '\0'; |
| #else |
| msg[l++] = '\n'; |
| msg[l] = '\0'; |
| if (where & L_LOG) { |
| /* Take full control of the log tty, and never close it. |
| * It's mine, all mine! Muhahahaha! */ |
| static int log_fd = -1; |
| |
| if (log_fd < 0) { |
| log_fd = STDERR_FILENO; |
| if (log_console) { |
| log_fd = device_open(log_console, O_WRONLY | O_NONBLOCK | O_NOCTTY); |
| if (log_fd < 0) { |
| bb_error_msg("can't log to %s", log_console); |
| where = L_CONSOLE; |
| } else { |
| close_on_exec_on(log_fd); |
| } |
| } |
| } |
| full_write(log_fd, msg, l); |
| if (log_fd == STDERR_FILENO) |
| return; /* don't print dup messages */ |
| } |
| #endif |
| |
| if (where & L_CONSOLE) { |
| /* Send console messages to console so people will see them. */ |
| full_write(STDERR_FILENO, msg, l); |
| } |
| } |
| |
| static void console_init(void) |
| { |
| #ifdef VT_OPENQRY |
| int vtno; |
| #endif |
| char *s; |
| |
| s = getenv("CONSOLE"); |
| if (!s) |
| s = getenv("console"); |
| #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__) |
| /* BSD people say their kernels do not open fd 0,1,2; they need this: */ |
| if (!s) |
| s = (char*)"/dev/console"; |
| #endif |
| if (s) { |
| int fd = open(s, O_RDWR | O_NONBLOCK | O_NOCTTY); |
| if (fd >= 0) { |
| dup2(fd, STDIN_FILENO); |
| dup2(fd, STDOUT_FILENO); |
| xmove_fd(fd, STDERR_FILENO); |
| } |
| dbg_message(L_LOG, "console='%s'", s); |
| } else { |
| /* Make sure fd 0,1,2 are not closed |
| * (so that they won't be used by future opens) */ |
| bb_sanitize_stdio(); |
| // Users report problems |
| // /* Make sure init can't be blocked by writing to stderr */ |
| // fcntl(STDERR_FILENO, F_SETFL, fcntl(STDERR_FILENO, F_GETFL) | O_NONBLOCK); |
| } |
| |
| s = getenv("TERM"); |
| #ifdef VT_OPENQRY |
| if (ioctl(STDIN_FILENO, VT_OPENQRY, &vtno) != 0) { |
| /* Not a linux terminal, probably serial console. |
| * Force the TERM setting to vt102 |
| * if TERM is set to linux (the default) */ |
| if (!s || strcmp(s, "linux") == 0) |
| putenv((char*)"TERM=vt102"); |
| # if !ENABLE_FEATURE_INIT_SYSLOG |
| log_console = NULL; |
| # endif |
| } else |
| #endif |
| if (!s) |
| putenv((char*)"TERM=" CONFIG_INIT_TERMINAL_TYPE); |
| } |
| |
| /* Set terminal settings to reasonable defaults. |
| * NB: careful, we can be called after vfork! */ |
| static void set_sane_term(void) |
| { |
| struct termios tty; |
| |
| tcgetattr(STDIN_FILENO, &tty); |
| |
| /* set control chars */ |
| tty.c_cc[VINTR] = 3; /* C-c */ |
| tty.c_cc[VQUIT] = 28; /* C-\ */ |
| tty.c_cc[VERASE] = 127; /* C-? */ |
| tty.c_cc[VKILL] = 21; /* C-u */ |
| tty.c_cc[VEOF] = 4; /* C-d */ |
| tty.c_cc[VSTART] = 17; /* C-q */ |
| tty.c_cc[VSTOP] = 19; /* C-s */ |
| tty.c_cc[VSUSP] = 26; /* C-z */ |
| |
| #ifdef __linux__ |
| /* use line discipline 0 */ |
| tty.c_line = 0; |
| #endif |
| |
| /* Make it be sane */ |
| #ifndef CRTSCTS |
| # define CRTSCTS 0 |
| #endif |
| /* added CRTSCTS to fix Debian bug 528560 */ |
| tty.c_cflag &= CBAUD | CBAUDEX | CSIZE | CSTOPB | PARENB | PARODD | CRTSCTS; |
| tty.c_cflag |= CREAD | HUPCL | CLOCAL; |
| |
| /* input modes */ |
| tty.c_iflag = ICRNL | IXON | IXOFF; |
| |
| /* output modes */ |
| tty.c_oflag = OPOST | ONLCR; |
| |
| /* local modes */ |
| tty.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE | IEXTEN; |
| |
| tcsetattr_stdin_TCSANOW(&tty); |
| } |
| |
| /* Open the new terminal device. |
| * NB: careful, we can be called after vfork! */ |
| static int open_stdio_to_tty(const char* tty_name) |
| { |
| /* empty tty_name means "use init's tty", else... */ |
| if (tty_name[0]) { |
| int fd; |
| |
| close(STDIN_FILENO); |
| /* fd can be only < 0 or 0: */ |
| fd = device_open(tty_name, O_RDWR); |
| if (fd) { |
| message(L_LOG | L_CONSOLE, "can't open %s: %s", |
| tty_name, strerror(errno)); |
| return 0; /* failure */ |
| } |
| dup2(STDIN_FILENO, STDOUT_FILENO); |
| dup2(STDIN_FILENO, STDERR_FILENO); |
| } |
| set_sane_term(); |
| return 1; /* success */ |
| } |
| |
| static void reset_sighandlers_and_unblock_sigs(void) |
| { |
| bb_signals(0 |
| + (1 << SIGUSR1) |
| + (1 << SIGUSR2) |
| + (1 << SIGTERM) |
| + (1 << SIGQUIT) |
| + (1 << SIGINT) |
| + (1 << SIGHUP) |
| + (1 << SIGTSTP) |
| + (1 << SIGSTOP) |
| , SIG_DFL); |
| sigprocmask_allsigs(SIG_UNBLOCK); |
| } |
| |
| /* Wrapper around exec: |
| * Takes string. |
| * If chars like '>' detected, execs '[-]/bin/sh -c "exec ......."'. |
| * Otherwise splits words on whitespace, deals with leading dash, |
| * and uses plain exec(). |
| * NB: careful, we can be called after vfork! |
| */ |
| static void init_exec(const char *command) |
| { |
| /* +8 allows to write VLA sizes below more efficiently: */ |
| unsigned command_size = strlen(command) + 8; |
| /* strlen(command) + strlen("exec ")+1: */ |
| char buf[command_size]; |
| /* strlen(command) / 2 + 4: */ |
| char *cmd[command_size / 2]; |
| int dash; |
| |
| dash = (command[0] == '-' /* maybe? && command[1] == '/' */); |
| command += dash; |
| |
| /* See if any special /bin/sh requiring characters are present */ |
| if (strpbrk(command, "~`!$^&*()=|\\{}[];\"'<>?") != NULL) { |
| sprintf(buf, "exec %s", command); /* excluding "-" */ |
| /* NB: LIBBB_DEFAULT_LOGIN_SHELL define has leading dash */ |
| cmd[0] = (char*)(LIBBB_DEFAULT_LOGIN_SHELL + !dash); |
| cmd[1] = (char*)"-c"; |
| cmd[2] = buf; |
| cmd[3] = NULL; |
| command = LIBBB_DEFAULT_LOGIN_SHELL + 1; |
| } else { |
| /* Convert command (char*) into cmd (char**, one word per string) */ |
| char *word, *next; |
| int i = 0; |
| next = strcpy(buf, command - dash); /* command including "-" */ |
| command = next + dash; |
| while ((word = strsep(&next, " \t")) != NULL) { |
| if (*word != '\0') { /* not two spaces/tabs together? */ |
| cmd[i] = word; |
| i++; |
| } |
| } |
| cmd[i] = NULL; |
| } |
| /* If we saw leading "-", it is interactive shell. |
| * Try harder to give it a controlling tty. |
| */ |
| if (ENABLE_FEATURE_INIT_SCTTY && dash) { |
| /* _Attempt_ to make stdin a controlling tty. */ |
| ioctl(STDIN_FILENO, TIOCSCTTY, 0 /*only try, don't steal*/); |
| } |
| /* Here command never contains the dash, cmd[0] might */ |
| BB_EXECVP(command, cmd); |
| message(L_LOG | L_CONSOLE, "can't run '%s': %s", command, strerror(errno)); |
| /* returns if execvp fails */ |
| } |
| |
| /* Used only by run_actions */ |
| static pid_t run(const struct init_action *a) |
| { |
| pid_t pid; |
| |
| /* Careful: don't be affected by a signal in vforked child */ |
| sigprocmask_allsigs(SIG_BLOCK); |
| if (BB_MMU && (a->action_type & ASKFIRST)) |
| pid = fork(); |
| else |
| pid = vfork(); |
| if (pid < 0) |
| message(L_LOG | L_CONSOLE, "can't fork"); |
| if (pid) { |
| sigprocmask_allsigs(SIG_UNBLOCK); |
| return pid; /* Parent or error */ |
| } |
| |
| /* Child */ |
| |
| /* Reset signal handlers that were set by the parent process */ |
| reset_sighandlers_and_unblock_sigs(); |
| |
| /* Create a new session and make ourself the process group leader */ |
| setsid(); |
| |
| /* Open the new terminal device */ |
| if (!open_stdio_to_tty(a->terminal)) |
| _exit(EXIT_FAILURE); |
| |
| /* NB: on NOMMU we can't wait for input in child, so |
| * "askfirst" will work the same as "respawn". */ |
| if (BB_MMU && (a->action_type & ASKFIRST)) { |
| static const char press_enter[] ALIGN1 = |
| #ifdef CUSTOMIZED_BANNER |
| #include CUSTOMIZED_BANNER |
| #endif |
| "\nPlease press Enter to activate this console. "; |
| char c; |
| /* |
| * Save memory by not exec-ing anything large (like a shell) |
| * before the user wants it. This is critical if swap is not |
| * enabled and the system has low memory. Generally this will |
| * be run on the second virtual console, and the first will |
| * be allowed to start a shell or whatever an init script |
| * specifies. |
| */ |
| dbg_message(L_LOG, "waiting for enter to start '%s'" |
| "(pid %d, tty '%s')\n", |
| a->command, getpid(), a->terminal); |
| full_write(STDOUT_FILENO, press_enter, sizeof(press_enter) - 1); |
| while (safe_read(STDIN_FILENO, &c, 1) == 1 && c != '\n') |
| continue; |
| } |
| |
| /* |
| * When a file named /.init_enable_core exists, setrlimit is called |
| * before processes are spawned to set core file size as unlimited. |
| * This is for debugging only. Don't use this is production, unless |
| * you want core dumps lying about.... |
| */ |
| if (ENABLE_FEATURE_INIT_COREDUMPS) { |
| if (access("/.init_enable_core", F_OK) == 0) { |
| struct rlimit limit; |
| limit.rlim_cur = RLIM_INFINITY; |
| limit.rlim_max = RLIM_INFINITY; |
| setrlimit(RLIMIT_CORE, &limit); |
| } |
| } |
| |
| /* Log the process name and args */ |
| message(L_LOG, "starting pid %u, tty '%s': '%s'", |
| (int)getpid(), a->terminal, a->command); |
| |
| /* Now run it. The new program will take over this PID, |
| * so nothing further in init.c should be run. */ |
| init_exec(a->command); |
| /* We're still here? Some error happened. */ |
| _exit(-1); |
| } |
| |
| static struct init_action *mark_terminated(pid_t pid) |
| { |
| struct init_action *a; |
| |
| if (pid > 0) { |
| update_utmp_DEAD_PROCESS(pid); |
| for (a = init_action_list; a; a = a->next) { |
| if (a->pid == pid) { |
| a->pid = 0; |
| return a; |
| } |
| } |
| } |
| return NULL; |
| } |
| |
| static void waitfor(pid_t pid) |
| { |
| /* waitfor(run(x)): protect against failed fork inside run() */ |
| if (pid <= 0) |
| return; |
| |
| /* Wait for any child (prevent zombies from exiting orphaned processes) |
| * but exit the loop only when specified one has exited. */ |
| while (1) { |
| pid_t wpid = wait(NULL); |
| mark_terminated(wpid); |
| /* Unsafe. SIGTSTP handler might have wait'ed it already */ |
| /*if (wpid == pid) break;*/ |
| /* More reliable: */ |
| if (kill(pid, 0)) |
| break; |
| } |
| } |
| |
| /* Run all commands of a particular type */ |
| static void run_actions(int action_type) |
| { |
| struct init_action *a; |
| |
| for (a = init_action_list; a; a = a->next) { |
| if (!(a->action_type & action_type)) |
| continue; |
| |
| if (a->action_type & (SYSINIT | WAIT | ONCE | CTRLALTDEL | SHUTDOWN)) { |
| pid_t pid = run(a); |
| if (a->action_type & (SYSINIT | WAIT | CTRLALTDEL | SHUTDOWN)) |
| waitfor(pid); |
| } |
| if (a->action_type & (RESPAWN | ASKFIRST)) { |
| /* Only run stuff with pid == 0. If pid != 0, |
| * it is already running |
| */ |
| if (a->pid == 0) |
| a->pid = run(a); |
| } |
| } |
| } |
| |
| static void new_init_action(uint8_t action_type, const char *command, const char *cons) |
| { |
| struct init_action *a, **nextp; |
| |
| /* Scenario: |
| * old inittab: |
| * ::shutdown:umount -a -r |
| * ::shutdown:swapoff -a |
| * new inittab: |
| * ::shutdown:swapoff -a |
| * ::shutdown:umount -a -r |
| * On reload, we must ensure entries end up in correct order. |
| * To achieve that, if we find a matching entry, we move it |
| * to the end. |
| */ |
| nextp = &init_action_list; |
| while ((a = *nextp) != NULL) { |
| /* Don't enter action if it's already in the list. |
| * This prevents losing running RESPAWNs. |
| */ |
| if (strcmp(a->command, command) == 0 |
| && strcmp(a->terminal, cons) == 0 |
| ) { |
| /* Remove from list */ |
| *nextp = a->next; |
| /* Find the end of the list */ |
| while (*nextp != NULL) |
| nextp = &(*nextp)->next; |
| a->next = NULL; |
| goto append; |
| } |
| nextp = &a->next; |
| } |
| |
| a = xzalloc(sizeof(*a) + strlen(command)); |
| |
| /* Append to the end of the list */ |
| append: |
| *nextp = a; |
| a->action_type = action_type; |
| strcpy(a->command, command); |
| safe_strncpy(a->terminal, cons, sizeof(a->terminal)); |
| dbg_message(L_LOG | L_CONSOLE, "command='%s' action=%x tty='%s'\n", |
| a->command, a->action_type, a->terminal); |
| } |
| |
| /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined, |
| * then parse_inittab() simply adds in some default |
| * actions (i.e., runs INIT_SCRIPT and then starts a pair |
| * of "askfirst" shells). If CONFIG_FEATURE_USE_INITTAB |
| * _is_ defined, but /etc/inittab is missing, this |
| * results in the same set of default behaviors. |
| */ |
| static void parse_inittab(void) |
| { |
| #if ENABLE_FEATURE_USE_INITTAB |
| char *token[4]; |
| parser_t *parser = config_open2("/etc/inittab", fopen_for_read); |
| |
| if (parser == NULL) |
| #endif |
| { |
| /* No inittab file - set up some default behavior */ |
| /* Sysinit */ |
| new_init_action(SYSINIT, INIT_SCRIPT, ""); |
| /* Askfirst shell on tty1-4 */ |
| new_init_action(ASKFIRST, bb_default_login_shell, ""); |
| //TODO: VC_1 instead of ""? "" is console -> ctty problems -> angry users |
| new_init_action(ASKFIRST, bb_default_login_shell, VC_2); |
| new_init_action(ASKFIRST, bb_default_login_shell, VC_3); |
| new_init_action(ASKFIRST, bb_default_login_shell, VC_4); |
| /* Reboot on Ctrl-Alt-Del */ |
| new_init_action(CTRLALTDEL, "reboot", ""); |
| /* Umount all filesystems on halt/reboot */ |
| new_init_action(SHUTDOWN, "umount -a -r", ""); |
| /* Swapoff on halt/reboot */ |
| new_init_action(SHUTDOWN, "swapoff -a", ""); |
| /* Restart init when a QUIT is received */ |
| new_init_action(RESTART, "init", ""); |
| return; |
| } |
| |
| #if ENABLE_FEATURE_USE_INITTAB |
| /* optional_tty:ignored_runlevel:action:command |
| * Delims are not to be collapsed and need exactly 4 tokens |
| */ |
| while (config_read(parser, token, 4, 0, "#:", |
| PARSE_NORMAL & ~(PARSE_TRIM | PARSE_COLLAPSE))) { |
| /* order must correspond to SYSINIT..RESTART constants */ |
| static const char actions[] ALIGN1 = |
| "sysinit\0""wait\0""once\0""respawn\0""askfirst\0" |
| "ctrlaltdel\0""shutdown\0""restart\0"; |
| int action; |
| char *tty = token[0]; |
| |
| if (!token[3]) /* less than 4 tokens */ |
| goto bad_entry; |
| action = index_in_strings(actions, token[2]); |
| if (action < 0 || !token[3][0]) /* token[3]: command */ |
| goto bad_entry; |
| /* turn .*TTY -> /dev/TTY */ |
| if (tty[0]) { |
| tty = concat_path_file("/dev/", skip_dev_pfx(tty)); |
| } |
| new_init_action(1 << action, token[3], tty); |
| if (tty[0]) |
| free(tty); |
| continue; |
| bad_entry: |
| message(L_LOG | L_CONSOLE, "Bad inittab entry at line %d", |
| parser->lineno); |
| } |
| config_close(parser); |
| #endif |
| } |
| |
| static void pause_and_low_level_reboot(unsigned magic) NORETURN; |
| static void pause_and_low_level_reboot(unsigned magic) |
| { |
| pid_t pid; |
| |
| /* Allow time for last message to reach serial console, etc */ |
| sleep(1); |
| |
| /* We have to fork here, since the kernel calls do_exit(EXIT_SUCCESS) |
| * in linux/kernel/sys.c, which can cause the machine to panic when |
| * the init process exits... */ |
| pid = vfork(); |
| if (pid == 0) { /* child */ |
| reboot(magic); |
| _exit(EXIT_SUCCESS); |
| } |
| while (1) |
| sleep(1); |
| } |
| |
| static void run_shutdown_and_kill_processes(void) |
| { |
| /* Run everything to be run at "shutdown". This is done _prior_ |
| * to killing everything, in case people wish to use scripts to |
| * shut things down gracefully... */ |
| run_actions(SHUTDOWN); |
| |
| message(L_CONSOLE | L_LOG, "The system is going down NOW!"); |
| |
| /* Send signals to every process _except_ pid 1 */ |
| kill(-1, SIGTERM); |
| message(L_CONSOLE, "Sent SIG%s to all processes", "TERM"); |
| sync(); |
| sleep(1); |
| |
| kill(-1, SIGKILL); |
| message(L_CONSOLE, "Sent SIG%s to all processes", "KILL"); |
| sync(); |
| /*sleep(1); - callers take care about making a pause */ |
| } |
| |
| /* Signal handling by init: |
| * |
| * For process with PID==1, on entry kernel sets all signals to SIG_DFL |
| * and unmasks all signals. However, for process with PID==1, |
| * default action (SIG_DFL) on any signal is to ignore it, |
| * even for special signals SIGKILL and SIGCONT. |
| * Also, any signal can be caught or blocked. |
| * (but SIGSTOP is still handled specially, at least in 2.6.20) |
| * |
| * We install two kinds of handlers, "immediate" and "delayed". |
| * |
| * Immediate handlers execute at any time, even while, say, sysinit |
| * is running. |
| * |
| * Delayed handlers just set a flag variable. The variable is checked |
| * in the main loop and acted upon. |
| * |
| * halt/poweroff/reboot and restart have immediate handlers. |
| * They only traverse linked list of struct action's, never modify it, |
| * this should be safe to do even in signal handler. Also they |
| * never return. |
| * |
| * SIGSTOP and SIGTSTP have immediate handlers. They just wait |
| * for SIGCONT to happen. |
| * |
| * SIGHUP has a delayed handler, because modifying linked list |
| * of struct action's from a signal handler while it is manipulated |
| * by the program may be disastrous. |
| * |
| * Ctrl-Alt-Del has a delayed handler. Not a must, but allowing |
| * it to happen even somewhere inside "sysinit" would be a bit awkward. |
| * |
| * There is a tiny probability that SIGHUP and Ctrl-Alt-Del will collide |
| * and only one will be remembered and acted upon. |
| */ |
| |
| /* The SIGPWR/SIGUSR[12]/SIGTERM handler */ |
| static void halt_reboot_pwoff(int sig) NORETURN; |
| static void halt_reboot_pwoff(int sig) |
| { |
| const char *m; |
| unsigned rb; |
| |
| /* We may call run() and it unmasks signals, |
| * including the one masked inside this signal handler. |
| * Testcase which would start multiple reboot scripts: |
| * while true; do reboot; done |
| * Preventing it: |
| */ |
| reset_sighandlers_and_unblock_sigs(); |
| |
| run_shutdown_and_kill_processes(); |
| |
| m = "halt"; |
| rb = RB_HALT_SYSTEM; |
| if (sig == SIGTERM) { |
| m = "reboot"; |
| rb = RB_AUTOBOOT; |
| } else if (sig == SIGUSR2) { |
| m = "poweroff"; |
| rb = RB_POWER_OFF; |
| } |
| message(L_CONSOLE, "Requesting system %s", m); |
| pause_and_low_level_reboot(rb); |
| /* not reached */ |
| } |
| |
| /* Handler for QUIT - exec "restart" action, |
| * else (no such action defined) do nothing */ |
| static void exec_restart_action(void) |
| { |
| struct init_action *a; |
| |
| for (a = init_action_list; a; a = a->next) { |
| if (!(a->action_type & RESTART)) |
| continue; |
| |
| /* Starting from here, we won't return. |
| * Thus don't need to worry about preserving errno |
| * and such. |
| */ |
| |
| reset_sighandlers_and_unblock_sigs(); |
| |
| run_shutdown_and_kill_processes(); |
| |
| #ifdef RB_ENABLE_CAD |
| /* Allow Ctrl-Alt-Del to reboot the system. |
| * This is how kernel sets it up for init, we follow suit. |
| */ |
| reboot(RB_ENABLE_CAD); /* misnomer */ |
| #endif |
| |
| if (open_stdio_to_tty(a->terminal)) { |
| dbg_message(L_CONSOLE, "Trying to re-exec %s", a->command); |
| /* Theoretically should be safe. |
| * But in practice, kernel bugs may leave |
| * unkillable processes, and wait() may block forever. |
| * Oh well. Hoping "new" init won't be too surprised |
| * by having children it didn't create. |
| */ |
| //while (wait(NULL) > 0) |
| // continue; |
| init_exec(a->command); |
| } |
| /* Open or exec failed */ |
| pause_and_low_level_reboot(RB_HALT_SYSTEM); |
| /* not reached */ |
| } |
| } |
| |
| /* The SIGSTOP/SIGTSTP handler |
| * NB: inside it, all signals except SIGCONT are masked |
| * via appropriate setup in sigaction(). |
| */ |
| static void stop_handler(int sig UNUSED_PARAM) |
| { |
| smallint saved_bb_got_signal; |
| int saved_errno; |
| |
| saved_bb_got_signal = bb_got_signal; |
| saved_errno = errno; |
| signal(SIGCONT, record_signo); |
| |
| while (1) { |
| pid_t wpid; |
| |
| if (bb_got_signal == SIGCONT) |
| break; |
| /* NB: this can accidentally wait() for a process |
| * which we waitfor() elsewhere! waitfor() must have |
| * code which is resilient against this. |
| */ |
| wpid = wait_any_nohang(NULL); |
| mark_terminated(wpid); |
| sleep(1); |
| } |
| |
| signal(SIGCONT, SIG_DFL); |
| errno = saved_errno; |
| bb_got_signal = saved_bb_got_signal; |
| } |
| |
| #if ENABLE_FEATURE_USE_INITTAB |
| static void reload_inittab(void) |
| { |
| struct init_action *a, **nextp; |
| |
| message(L_LOG, "reloading /etc/inittab"); |
| |
| /* Disable old entries */ |
| for (a = init_action_list; a; a = a->next) |
| a->action_type = 0; |
| |
| /* Append new entries, or modify existing entries |
| * (incl. setting a->action_type) if cmd and device name |
| * match new ones. End result: only entries with |
| * a->action_type == 0 are stale. |
| */ |
| parse_inittab(); |
| |
| #if ENABLE_FEATURE_KILL_REMOVED |
| /* Kill stale entries */ |
| /* Be nice and send SIGTERM first */ |
| for (a = init_action_list; a; a = a->next) |
| if (a->action_type == 0 && a->pid != 0) |
| kill(a->pid, SIGTERM); |
| if (CONFIG_FEATURE_KILL_DELAY) { |
| /* NB: parent will wait in NOMMU case */ |
| if ((BB_MMU ? fork() : vfork()) == 0) { /* child */ |
| sleep(CONFIG_FEATURE_KILL_DELAY); |
| for (a = init_action_list; a; a = a->next) |
| if (a->action_type == 0 && a->pid != 0) |
| kill(a->pid, SIGKILL); |
| _exit(EXIT_SUCCESS); |
| } |
| } |
| #endif |
| |
| /* Remove stale entries and SYSINIT entries. |
| * We never rerun SYSINIT entries anyway, |
| * removing them too saves a few bytes |
| */ |
| nextp = &init_action_list; |
| while ((a = *nextp) != NULL) { |
| /* |
| * Why pid == 0 check? |
| * Process can be removed from inittab and added *later*. |
| * If we delete its entry but process still runs, |
| * duplicate is spawned when the entry is re-added. |
| */ |
| if ((a->action_type & ~SYSINIT) == 0 && a->pid == 0) { |
| *nextp = a->next; |
| free(a); |
| } else { |
| nextp = &a->next; |
| } |
| } |
| |
| /* Not needed: */ |
| /* run_actions(RESPAWN | ASKFIRST); */ |
| /* - we return to main loop, which does this automagically */ |
| } |
| #endif |
| |
| static int check_delayed_sigs(void) |
| { |
| int sigs_seen = 0; |
| |
| while (1) { |
| smallint sig = bb_got_signal; |
| |
| if (!sig) |
| return sigs_seen; |
| bb_got_signal = 0; |
| sigs_seen = 1; |
| #if ENABLE_FEATURE_USE_INITTAB |
| if (sig == SIGHUP) |
| reload_inittab(); |
| #endif |
| if (sig == SIGINT) |
| run_actions(CTRLALTDEL); |
| if (sig == SIGQUIT) { |
| exec_restart_action(); |
| /* returns only if no restart action defined */ |
| } |
| if ((1 << sig) & (0 |
| #ifdef SIGPWR |
| + (1 << SIGPWR) |
| #endif |
| + (1 << SIGUSR1) |
| + (1 << SIGUSR2) |
| + (1 << SIGTERM) |
| )) { |
| halt_reboot_pwoff(sig); |
| } |
| } |
| } |
| |
| #if DEBUG_SEGV_HANDLER |
| static |
| void handle_sigsegv(int sig, siginfo_t *info, void *ucontext) |
| { |
| long ip; |
| ucontext_t *uc; |
| |
| uc = ucontext; |
| ip = uc->uc_mcontext.gregs[REG_EIP]; |
| fdprintf(2, "signal:%d address:0x%lx ip:0x%lx\n", |
| sig, |
| /* this is void*, but using %p would print "(null)" |
| * even for ptrs which are not exactly 0, but, say, 0x123: |
| */ |
| (long)info->si_addr, |
| ip); |
| { |
| /* glibc extension */ |
| void *array[50]; |
| int size; |
| size = backtrace(array, 50); |
| backtrace_symbols_fd(array, size, 2); |
| } |
| for (;;) sleep(9999); |
| } |
| #endif |
| |
| static void sleep_much(void) |
| { |
| sleep(30 * 24*60*60); |
| } |
| |
| int init_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
| int init_main(int argc UNUSED_PARAM, char **argv) |
| { |
| if (argv[1] && strcmp(argv[1], "-q") == 0) { |
| return kill(1, SIGHUP); |
| } |
| |
| #if DEBUG_SEGV_HANDLER |
| { |
| struct sigaction sa; |
| memset(&sa, 0, sizeof(sa)); |
| sa.sa_sigaction = handle_sigsegv; |
| sa.sa_flags = SA_SIGINFO; |
| sigaction(SIGSEGV, &sa, NULL); |
| sigaction(SIGILL, &sa, NULL); |
| sigaction(SIGFPE, &sa, NULL); |
| sigaction(SIGBUS, &sa, NULL); |
| } |
| #endif |
| |
| if (!DEBUG_INIT) { |
| /* Expect to be invoked as init with PID=1 or be invoked as linuxrc */ |
| if (getpid() != 1 |
| && (!ENABLE_LINUXRC || applet_name[0] != 'l') /* not linuxrc? */ |
| ) { |
| bb_error_msg_and_die("must be run as PID 1"); |
| } |
| #ifdef RB_DISABLE_CAD |
| /* Turn off rebooting via CTL-ALT-DEL - we get a |
| * SIGINT on CAD so we can shut things down gracefully... */ |
| reboot(RB_DISABLE_CAD); /* misnomer */ |
| #endif |
| } |
| |
| /* If, say, xmalloc would ever die, we don't want to oops kernel |
| * by exiting. |
| * NB: we set die_func *after* PID 1 check and bb_show_usage. |
| * Otherwise, for example, "init u" ("please rexec yourself" |
| * command for sysvinit) will show help text (which isn't too bad), |
| * *and sleep forever* (which is bad!) |
| */ |
| die_func = sleep_much; |
| |
| /* Figure out where the default console should be */ |
| console_init(); |
| set_sane_term(); |
| xchdir("/"); |
| setsid(); |
| |
| /* Make sure environs is set to something sane */ |
| putenv((char *) "HOME=/"); |
| putenv((char *) bb_PATH_root_path); |
| putenv((char *) "SHELL=/bin/sh"); |
| putenv((char *) "USER=root"); /* needed? why? */ |
| |
| if (argv[1]) |
| xsetenv("RUNLEVEL", argv[1]); |
| |
| #if !ENABLE_FEATURE_INIT_QUIET |
| /* Hello world */ |
| message(L_CONSOLE | L_LOG, "init started: %s", bb_banner); |
| #endif |
| |
| #if 0 |
| /* It's 2013, does anyone really still depend on this? */ |
| /* If you do, consider adding swapon to sysinit actions then! */ |
| /* struct sysinfo is linux-specific */ |
| # ifdef __linux__ |
| /* Make sure there is enough memory to do something useful. */ |
| /*if (ENABLE_SWAPONOFF) - WRONG: we may have non-bbox swapon*/ { |
| struct sysinfo info; |
| |
| if (sysinfo(&info) == 0 |
| && (info.mem_unit ? info.mem_unit : 1) * (long long)info.totalram < 1024*1024 |
| ) { |
| message(L_CONSOLE, "Low memory, forcing swapon"); |
| /* swapon -a requires /proc typically */ |
| new_init_action(SYSINIT, "mount -t proc proc /proc", ""); |
| /* Try to turn on swap */ |
| new_init_action(SYSINIT, "swapon -a", ""); |
| run_actions(SYSINIT); /* wait and removing */ |
| } |
| } |
| # endif |
| #endif |
| |
| /* Check if we are supposed to be in single user mode */ |
| if (argv[1] |
| && (strcmp(argv[1], "single") == 0 || strcmp(argv[1], "-s") == 0 || LONE_CHAR(argv[1], '1')) |
| ) { |
| /* ??? shouldn't we set RUNLEVEL="b" here? */ |
| /* Start a shell on console */ |
| new_init_action(RESPAWN, bb_default_login_shell, ""); |
| } else { |
| /* Not in single user mode - see what inittab says */ |
| |
| /* NOTE that if CONFIG_FEATURE_USE_INITTAB is NOT defined, |
| * then parse_inittab() simply adds in some default |
| * actions (i.e., INIT_SCRIPT and a pair |
| * of "askfirst" shells) */ |
| parse_inittab(); |
| } |
| |
| #if ENABLE_SELINUX |
| if (getenv("SELINUX_INIT") == NULL) { |
| int enforce = 0; |
| |
| putenv((char*)"SELINUX_INIT=YES"); |
| if (selinux_init_load_policy(&enforce) == 0) { |
| BB_EXECVP(argv[0], argv); |
| } else if (enforce > 0) { |
| /* SELinux in enforcing mode but load_policy failed */ |
| message(L_CONSOLE, "can't load SELinux Policy. " |
| "Machine is in enforcing mode. Halting now."); |
| return EXIT_FAILURE; |
| } |
| } |
| #endif |
| |
| if (ENABLE_FEATURE_INIT_MODIFY_CMDLINE) { |
| /* Make the command line just say "init" - that's all, nothing else */ |
| strncpy(argv[0], "init", strlen(argv[0])); |
| /* Wipe argv[1]-argv[N] so they don't clutter the ps listing */ |
| while (*++argv) |
| nuke_str(*argv); |
| } |
| |
| /* Set up signal handlers */ |
| if (!DEBUG_INIT) { |
| struct sigaction sa; |
| |
| /* Stop handler must allow only SIGCONT inside itself */ |
| memset(&sa, 0, sizeof(sa)); |
| sigfillset(&sa.sa_mask); |
| sigdelset(&sa.sa_mask, SIGCONT); |
| sa.sa_handler = stop_handler; |
| /* NB: sa_flags doesn't have SA_RESTART. |
| * It must be able to interrupt wait(). |
| */ |
| sigaction_set(SIGTSTP, &sa); /* pause */ |
| /* Does not work as intended, at least in 2.6.20. |
| * SIGSTOP is simply ignored by init: |
| */ |
| sigaction_set(SIGSTOP, &sa); /* pause */ |
| |
| /* These signals must interrupt wait(), |
| * setting handler without SA_RESTART flag. |
| */ |
| bb_signals_recursive_norestart(0 |
| + (1 << SIGINT) /* Ctrl-Alt-Del */ |
| + (1 << SIGQUIT) /* re-exec another init */ |
| #ifdef SIGPWR |
| + (1 << SIGPWR) /* halt */ |
| #endif |
| + (1 << SIGUSR1) /* halt */ |
| + (1 << SIGTERM) /* reboot */ |
| + (1 << SIGUSR2) /* poweroff */ |
| #if ENABLE_FEATURE_USE_INITTAB |
| + (1 << SIGHUP) /* reread /etc/inittab */ |
| #endif |
| , record_signo); |
| } |
| |
| /* Now run everything that needs to be run */ |
| /* First run the sysinit command */ |
| run_actions(SYSINIT); |
| check_delayed_sigs(); |
| /* Next run anything that wants to block */ |
| run_actions(WAIT); |
| check_delayed_sigs(); |
| /* Next run anything to be run only once */ |
| run_actions(ONCE); |
| |
| /* Now run the looping stuff for the rest of forever. |
| */ |
| while (1) { |
| int maybe_WNOHANG; |
| |
| maybe_WNOHANG = check_delayed_sigs(); |
| |
| /* (Re)run the respawn/askfirst stuff */ |
| run_actions(RESPAWN | ASKFIRST); |
| maybe_WNOHANG |= check_delayed_sigs(); |
| |
| /* Don't consume all CPU time - sleep a bit */ |
| sleep(1); |
| maybe_WNOHANG |= check_delayed_sigs(); |
| |
| /* Wait for any child process(es) to exit. |
| * |
| * If check_delayed_sigs above reported that a signal |
| * was caught, wait will be nonblocking. This ensures |
| * that if SIGHUP has reloaded inittab, respawn and askfirst |
| * actions will not be delayed until next child death. |
| */ |
| if (maybe_WNOHANG) |
| maybe_WNOHANG = WNOHANG; |
| while (1) { |
| pid_t wpid; |
| struct init_action *a; |
| |
| /* If signals happen _in_ the wait, they interrupt it, |
| * bb_signals_recursive_norestart set them up that way |
| */ |
| wpid = waitpid(-1, NULL, maybe_WNOHANG); |
| if (wpid <= 0) |
| break; |
| |
| a = mark_terminated(wpid); |
| if (a) { |
| message(L_LOG, "process '%s' (pid %d) exited. " |
| "Scheduling for restart.", |
| a->command, wpid); |
| } |
| /* See if anyone else is waiting to be reaped */ |
| maybe_WNOHANG = WNOHANG; |
| } |
| } /* while (1) */ |
| } |
| |
| //usage:#define linuxrc_trivial_usage NOUSAGE_STR |
| //usage:#define linuxrc_full_usage "" |
| |
| //usage:#define init_trivial_usage |
| //usage: "" |
| //usage:#define init_full_usage "\n\n" |
| //usage: "Init is the first process started during boot. It never exits." |
| //usage: IF_FEATURE_USE_INITTAB( |
| //usage: "\n""It (re)spawns children according to /etc/inittab." |
| //usage: ) |
| //usage: IF_NOT_FEATURE_USE_INITTAB( |
| //usage: "\n""This version of init doesn't use /etc/inittab," |
| //usage: "\n""has fixed set of processed to run." |
| //usage: ) |
| //usage: |
| //usage:#define init_notes_usage |
| //usage: "This version of init is designed to be run only by the kernel.\n" |
| //usage: "\n" |
| //usage: "BusyBox init doesn't support multiple runlevels. The runlevels field of\n" |
| //usage: "the /etc/inittab file is completely ignored by BusyBox init. If you want\n" |
| //usage: "runlevels, use sysvinit.\n" |
| //usage: "\n" |
| //usage: "BusyBox init works just fine without an inittab. If no inittab is found,\n" |
| //usage: "it has the following default behavior:\n" |
| //usage: "\n" |
| //usage: " ::sysinit:/etc/init.d/rcS\n" |
| //usage: " ::askfirst:/bin/sh\n" |
| //usage: " ::ctrlaltdel:/sbin/reboot\n" |
| //usage: " ::shutdown:/sbin/swapoff -a\n" |
| //usage: " ::shutdown:/bin/umount -a -r\n" |
| //usage: " ::restart:/sbin/init\n" |
| //usage: " tty2::askfirst:/bin/sh\n" |
| //usage: " tty3::askfirst:/bin/sh\n" |
| //usage: " tty4::askfirst:/bin/sh\n" |
| //usage: "\n" |
| //usage: "If you choose to use an /etc/inittab file, the inittab entry format is as follows:\n" |
| //usage: "\n" |
| //usage: " <id>:<runlevels>:<action>:<process>\n" |
| //usage: "\n" |
| //usage: " <id>:\n" |
| //usage: "\n" |
| //usage: " WARNING: This field has a non-traditional meaning for BusyBox init!\n" |
| //usage: " The id field is used by BusyBox init to specify the controlling tty for\n" |
| //usage: " the specified process to run on. The contents of this field are\n" |
| //usage: " appended to \"/dev/\" and used as-is. There is no need for this field to\n" |
| //usage: " be unique, although if it isn't you may have strange results. If this\n" |
| //usage: " field is left blank, then the init's stdin/out will be used.\n" |
| //usage: "\n" |
| //usage: " <runlevels>:\n" |
| //usage: "\n" |
| //usage: " The runlevels field is completely ignored.\n" |
| //usage: "\n" |
| //usage: " <action>:\n" |
| //usage: "\n" |
| //usage: " Valid actions include: sysinit, respawn, askfirst, wait,\n" |
| //usage: " once, restart, ctrlaltdel, and shutdown.\n" |
| //usage: "\n" |
| //usage: " The available actions can be classified into two groups: actions\n" |
| //usage: " that are run only once, and actions that are re-run when the specified\n" |
| //usage: " process exits.\n" |
| //usage: "\n" |
| //usage: " Run only-once actions:\n" |
| //usage: "\n" |
| //usage: " 'sysinit' is the first item run on boot. init waits until all\n" |
| //usage: " sysinit actions are completed before continuing. Following the\n" |
| //usage: " completion of all sysinit actions, all 'wait' actions are run.\n" |
| //usage: " 'wait' actions, like 'sysinit' actions, cause init to wait until\n" |
| //usage: " the specified task completes. 'once' actions are asynchronous,\n" |
| //usage: " therefore, init does not wait for them to complete. 'restart' is\n" |
| //usage: " the action taken to restart the init process. By default this should\n" |
| //usage: " simply run /sbin/init, but can be a script which runs pivot_root or it\n" |
| //usage: " can do all sorts of other interesting things. The 'ctrlaltdel' init\n" |
| //usage: " actions are run when the system detects that someone on the system\n" |
| //usage: " console has pressed the CTRL-ALT-DEL key combination. Typically one\n" |
| //usage: " wants to run 'reboot' at this point to cause the system to reboot.\n" |
| //usage: " Finally the 'shutdown' action specifies the actions to taken when\n" |
| //usage: " init is told to reboot. Unmounting filesystems and disabling swap\n" |
| //usage: " is a very good here.\n" |
| //usage: "\n" |
| //usage: " Run repeatedly actions:\n" |
| //usage: "\n" |
| //usage: " 'respawn' actions are run after the 'once' actions. When a process\n" |
| //usage: " started with a 'respawn' action exits, init automatically restarts\n" |
| //usage: " it. Unlike sysvinit, BusyBox init does not stop processes from\n" |
| //usage: " respawning out of control. The 'askfirst' actions acts just like\n" |
| //usage: " respawn, except that before running the specified process it\n" |
| //usage: " displays the line \"Please press Enter to activate this console.\"\n" |
| //usage: " and then waits for the user to press enter before starting the\n" |
| //usage: " specified process.\n" |
| //usage: "\n" |
| //usage: " Unrecognized actions (like initdefault) will cause init to emit an\n" |
| //usage: " error message, and then go along with its business. All actions are\n" |
| //usage: " run in the order they appear in /etc/inittab.\n" |
| //usage: "\n" |
| //usage: " <process>:\n" |
| //usage: "\n" |
| //usage: " Specifies the process to be executed and its command line.\n" |
| //usage: "\n" |
| //usage: "Example /etc/inittab file:\n" |
| //usage: "\n" |
| //usage: " # This is run first except when booting in single-user mode\n" |
| //usage: " #\n" |
| //usage: " ::sysinit:/etc/init.d/rcS\n" |
| //usage: " \n" |
| //usage: " # /bin/sh invocations on selected ttys\n" |
| //usage: " #\n" |
| //usage: " # Start an \"askfirst\" shell on the console (whatever that may be)\n" |
| //usage: " ::askfirst:-/bin/sh\n" |
| //usage: " # Start an \"askfirst\" shell on /dev/tty2-4\n" |
| //usage: " tty2::askfirst:-/bin/sh\n" |
| //usage: " tty3::askfirst:-/bin/sh\n" |
| //usage: " tty4::askfirst:-/bin/sh\n" |
| //usage: " \n" |
| //usage: " # /sbin/getty invocations for selected ttys\n" |
| //usage: " #\n" |
| //usage: " tty4::respawn:/sbin/getty 38400 tty4\n" |
| //usage: " tty5::respawn:/sbin/getty 38400 tty5\n" |
| //usage: " \n" |
| //usage: " \n" |
| //usage: " # Example of how to put a getty on a serial line (for a terminal)\n" |
| //usage: " #\n" |
| //usage: " #::respawn:/sbin/getty -L ttyS0 9600 vt100\n" |
| //usage: " #::respawn:/sbin/getty -L ttyS1 9600 vt100\n" |
| //usage: " #\n" |
| //usage: " # Example how to put a getty on a modem line\n" |
| //usage: " #::respawn:/sbin/getty 57600 ttyS2\n" |
| //usage: " \n" |
| //usage: " # Stuff to do when restarting the init process\n" |
| //usage: " ::restart:/sbin/init\n" |
| //usage: " \n" |
| //usage: " # Stuff to do before rebooting\n" |
| //usage: " ::ctrlaltdel:/sbin/reboot\n" |
| //usage: " ::shutdown:/bin/umount -a -r\n" |
| //usage: " ::shutdown:/sbin/swapoff -a\n" |