Rhel 7/CentOS 7 boot process
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The RHEL 7 boot process begins with the BIOS or UEFI firmware initializing hardware and searching for the boot loader. The boot loader then loads the kernel and initramfs into memory, where initramfs provides drivers and systemd to execute units like mounting the actual root file system. Finally, systemd switches the root file system to the hard disk and starts the default target to present the graphical or text login screen.
Rhel 7/CentOS 7 boot process
- 1. RHEL 7 Boot Process Team ElectroMech 1
- 2. RHEL7 Boot Process ... Boot Loader Grub23. Read and passes control to boot loader Boot Loader Menu4. Read config file from disk and present boot menu Loads kernel and initramfs5. Load kernel & initramfs in memory, initramfs provides drivers and entire usable systemd BIOS UEFI1. POST and initialize some hardware MBR UEFI Firmware2. MBR or UEFI firmware search boot loader 2
- 3. RHEL7 Boot Process systemd(from initramfs) execute all units initrd.target8. initrd.target includes mounting actual root f/s on /sysroot, mounts /etc/fstab systemd switch rootfs to harddisk9. root f/s will be switched to /sysroot and reexecute using hardidisk systemd systemd looks & start default target, GUI or text login10. systemd start default target configured in file or CLI and present login screen. Boot Loader pass on control to kernel6. Option specified on CLI or config file /etc/grub.d /etc/default/grub /boot/grub/grub.cfg Execute /sbin/init systemd PID 17. Kernel initializes all h/w with initramfs, execute /sbin/init = systemd (working copy) from initramfs as PID 1 and udev daemon 3