FileSystem: Initialization

FileSystem: Initialization

       After the kernel started up，following with file system.

   init is the first user space process spawned by the kernel after completion of the boot process. And init can exist in a single runlevel(7 levels) at any given time.  Init invokes some scripts under a directory called /etc/rc.d/init.d that includes every service script like nfs,syslog. Init also reads the system configuration file /etc/inittab. Refer to man init and man inittab if want details.

    The initrd is a temporary filesystem commonly used in the boot process of the Linux kernel. It is typically used for making preparations before the real root file can be mounted.