/* oneit.c - tiny init replacement to launch a single child process. * * Copyright 2005, 2007 by Rob Landley <rob@landley.net>. USE_ONEIT(NEWTOY(oneit, "^<1c:p", TOYFLAG_SBIN)) config ONEIT bool "oneit" default y help usage: oneit [-p] [-c /dev/tty0] command [...] A simple init program that runs a single supplied command line with a controlling tty (so CTRL-C can kill it). -p Power off instead of rebooting when command exits. -c Which console device to use. The oneit command runs the supplied command line as a child process (because PID 1 has signals blocked), attached to /dev/tty0, in its own session. Then oneit reaps zombies until the child exits, at which point it reboots (or with -p, powers off) the system. */ #define FOR_oneit #include "toys.h" #include <sys/reboot.h> GLOBALS( char *console; ) // The minimum amount of work necessary to get ctrl-c and such to work is: // // - Fork a child (PID 1 is special: can't exit, has various signals blocked). // - Do a setsid() (so we have our own session). // - In the child, attach stdio to /dev/tty0 (/dev/console is special) // - Exec the rest of the command line. // // PID 1 then reaps zombies until the child process it spawned exits, at which // point it calls sync() and reboot(). I could stick a kill -1 in there. void oneit_main(void) { int i; pid_t pid; // Create a new child process. pid = vfork(); if (pid) { // pid 1 just reaps zombies until it gets its child, then halts the system. while (pid != wait(&i)); sync(); // PID 1 can't call reboot() because it kills the task that calls it, // which causes the kernel to panic before the actual reboot happens. if (!vfork()) reboot((toys.optflags & FLAG_p) ? RB_POWER_OFF : RB_AUTOBOOT); sleep(5); _exit(1); } // Redirect stdio to /dev/tty0, with new session ID, so ctrl-c works. setsid(); for (i=0; i<3; i++) { close(i); // Remember, O_CLOEXEC is backwards for xopen() xopen(TT.console ? TT.console : "/dev/tty0", O_RDWR|O_CLOEXEC); } // Can't xexec() here, because we vforked so we don't want to error_exit(). toy_exec(toys.optargs); execvp(*toys.optargs, toys.optargs); _exit(127); }