Centos7 system startup process

1. UEFI or BIOS initialization, run POST power-on self-test

2. Select the boot device, Boot Sequence

The system startup sequence generally includes: Optical drive, USB flash drive, hard disk A, hard disk B. Search each boot device in order. The first device with a boot program is the device used for this startup.

3. Boot loader, load /boot partition file system driver

4. Load loader configuration file: /etc/grub.d/ /etc/default/grub /boot/ grub2/grub.cfg

(Recommended tutorial: centos usage tutorial)

5. Load initramfs driver module and kernel vmlinuz

6. Kernel initialization , centos7 uses systemd instead of init

7. Execute all units of initrd.target, including mounting /etc/fstab

8. Switch from initramfs and file system to the disk root directory

9. Systemd executes the default target configuration and the configuration file /etc/systemd/system/default.target

10. Systemd executes sysinit.target to initialize the system and basic.target to prepare the operating system

11. systemd starts the local and server services under multi-user.target

12. systemd executes /etc/rc.d/rc.local under multi-user.target

13 , systemd executes getty.target and login service under multi-user.target

14. Systemd executes the services required by graphical

Related video tutorial recommendations: linux video tutorial

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