5.7. init()

static int init(void * unused)
{
	lock_kernel();
(1)
	do_basic_setup();

(2)
	prepare_namespace();

	/*
	 * Ok, we have completed the initial bootup, and
	 * we're essentially up and running. Get rid of the
	 * initmem segments and start the user-mode stuff..
	 */
(3)
	free_initmem();
	unlock_kernel();

(4)
	if (open("/dev/console", O_RDWR, 0) < 0)
		printk("Warning: unable to open an initial console.\n");

	(void) dup(0);
	(void) dup(0);
	
	/*
	 * We try each of these until one succeeds.
	 *
	 * The Bourne shell can be used instead of init if we are 
	 * trying to recover a really broken machine.
	 */

	if (execute_command)
		execve(execute_command,argv_init,envp_init);
(5)
	execve("/sbin/init",argv_init,envp_init);
	execve("/etc/init",argv_init,envp_init);
	execve("/bin/init",argv_init,envp_init);
	execve("/bin/sh",argv_init,envp_init);
(6)
	execve("/sbin/init",argv_init,envp_init);
	panic("No init found.  Try passing init= option to kernel.");
}