Let’s describe Linux Boot Process:
| BIOS |
Basic INPUT/OUTPUT System. Executes MBR |
| MBR |
Master Boot Record Executes GRUB |
| GRUB |
Grand Unified Bootloader Executes kernel |
| KERNEL |
Kernel Executes /sbin/init |
| INIT |
Init Executes Run level programs |
| Run Level | Run Level Programs are executed from /etc/rc.d/rc*.d/ |
- As power comes up the BIOS is given control
- BIOS runs self tests, usually including cursory memory tests.
- The BIOS then loads the first sector of the disk to be used for booting and transfers control to it.
- The MBR code varies. One version will chain to the code in the first sector of the boot partition (Windows), another will load a bootloader. Windows boot proceeds from code and information in the boot partition.
- The bootloader chooses kernel location and version
- The bootloader prepares kernel and initrd image in memory, transfers control to kernel
- Loading kernel modules
- Discovering hardware and load additional kernel modules to support it
- Looking for disks
- R/O mount of / partition so that it can potentially be checked and repaired
- init process spawn
- /etc/inittab read and executing
- Mounting all FSes from /etc/fstab
- runlevels running (based on default runlevel in /etc/inittab) or another init method such as systemd or upstart
- rc.local
- login prompt
Source:
- http://unix.stackexchange.com/questions/27034/discribe-in-details-tha-boot-process-of-any-linux-system
- http://www.thegeekstuff.com/2011/02/linux-boot-process/
- Watch video here
- http://www.slideshare.net/dominiquec/understanding-the-boot-process
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