Thuc notes - Linux boot process
Part of series osdev |
General steps:
- Power on.
- BIOS/UEFI.
- Bootloader.
- Kernel load.
- Run level.
BIOS/UEFI
- Read more at https://thuc.space/posts/firmware-boot-process/
Bootloader
- Choose OS.
- Choose kernel.
- Load and execute kernel and initrd.
Kernel load
- initrd loads a temporary root file system into memory until real file system is mounted.
- Start load kernel and real file system.
- Mount real root file system.
- Execute /sbin/init as 1st program, can be systemd or SysV init.
Run level
- Mount file system.
- Decide what run-level will be run.
- Run scripts from /etc/rc[0-6S].d directory bases on run-level.
- /etc/rc[0-6S].d/S…. : is run when starting.
- /etc/rc[0-6S].d/K…. : is run when stopping.
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