FS - How does OS load File System

BIOS(code stored on ROM)

At BIOS session, several tasks are executed:

1. Power-on self test (POST), making suring: memory, disk,screen,ect. are in good condition
   • so it knows where to load the boot program( on DISK)
   • also prepare memory(run process) and disk(boot program)
2. Load and transfer control to boot program
3. Provide drivers for all devices,

Boot(code stored on DISK)

1. Set up stack, clear BSS, uncompress kernel, then transfer control to Kernel

2. Idle process(pid=0) is created; set up initial page tables, turn on address translation

3. Initialize rest of kernel

   • create vfs_root_vnode
   • set the “cwd” of idle/init process
   • make the null, zero, and tty devices using “mknod”
     • “/dev”
     • “/dev/null” “/dev/zero”,
     • “/dev/tty0” “/dev/tty1”
   • create the “init” process(pid=1),
     which is the ancestor of all other user processes
   • invoke the scheduler

Kernel(code stored on disk)

1. Now the File System is ready to use
2. Also need to execute other configuration