本文共 4072 字，大约阅读时间需要 13 分钟。
android: v2.3.41. init.clinux内核起来后，init是android的第一个用户进程system/core/init/init.cint main(int argc, char **argv){/******创建linux 根文件系统的目录***********/ mkdir("/dev", 0755); mkdir("/proc", 0755); mkdir("/sys", 0755); mount("tmpfs", "/dev", "tmpfs", 0, "mode=0755"); mkdir("/dev/pts", 0755); mkdir("/dev/socket", 0755); mount("devpts", "/dev/pts", "devpts", 0, NULL); mount("proc", "/proc", "proc", 0, NULL); mount("sysfs", "/sys", "sysfs", 0, NULL); //打开标准输入，输出，错误文件描述符 open_devnull_stdio(); //读取并解析init.rc init_parse_config_file("/init.rc"); //通过/proc/cmdline得到启动命令 //从/proc/cmdline 中提取信息内核启动参数,并保存到全局变量 import_kernel_cmdline(0); //通过/proc/cpuinfo 得到硬件名 get_hardware_name(hardware, &revision); //读取并且解析硬件相关的Init脚本文件 snprintf(tmp, sizeof(tmp), "/init.%s.rc", hardware); init_parse_config_file(tmp);/******触发在init脚本文件中名字为early-init的action并且执行命令*******/ action_for_each_trigger("early-init", action_add_queue_tail); //串口初始化 queue_builtin_action(console_init_action, "console_init");}static int console_init_action(int nargs, char **args){/***判断是否有控制台，如果没有就用默认的*********/ if (console[0]) { snprintf(tmp, sizeof(tmp), "/dev/%s", console); console_name = strdup(tmp); }/*****打开console,如果cmdline中没有指定console则打开/dev/console fd = open(console_name, O_RDWR);/*****#define INIT_IMAGE_FILE "/initlogo.rle"@*读取initlogo.rle.是放在根文件系统下的一张565 rle压缩的开机logo@*如果打开成功则在/dev/graphics/fb0显示logo,如果失败，则打开/dev/tty0显示@*ANDROID 文本*/ if( load_565rle_image(INIT_IMAGE_FILE) ) { fd = open("/dev/tty0", O_WRONLY); if (fd >= 0) { const char *msg; msg = "\n" "\n" "\n" "\n" "\n" "\n" "\n" // console is 40 cols x 30 lines "\n" "\n" "\n" "\n" "\n" "\n" "\n" " A N D R O I D "; write(fd, msg, strlen(msg)); close(fd); } }}2. init脚本语言Android中使用启动脚本init.rc,init启动脚本的路径system/coer/rootdir/init.rcinit.rc被安装到根文件系统中，被init可执行程序解析init.rc脚本的使用可以参考system/core/init/readme.txt所有的都是以行为单位，各种记号由空格来隔开反斜杠号可用于在记号间插入空格1) Action 动作其实就是一系列的命令commands,Actions都有一个trigger触发器，用来决定action的执行时间Actions take the form of:on on early-init on init on fs on post-fs on boot on property:ro.secure=0 on property:ro.kernel.qemu=1 on property:persist.service.adb.enable=1 这些触发是由init.c里的函数action_for_each_trigger来决定的 action_for_each_trigger("early-init", action_add_queue_tail); action_for_each_trigger("init", action_add_queue_tail); action_for_each_trigger("early-fs", action_add_queue_tail); action_for_each_trigger("fs", action_add_queue_tail); action_for_each_trigger("post-fs", action_add_queue_tail); action_for_each_trigger("early-boot", action_add_queue_tail); action_for_each_trigger("boot", action_add_queue_tail);2)services服务services表示启动一个可执行程序，options选项是服务的附加内容用于配合服务使用service [ ]* 转载地址：http://exkni.baihongyu.com/