Linux Administration/System Architecture/Boot Sequence

This lesson covers the boot sequence.

Objectives and Skills
Objectives and skills for the boot sequence portion of Linux+ certification include:
 * Boot the system
 * Provide common commands to the boot loader and options to the kernel at boot time
 * Demonstrate knowledge of the boot sequence from BIOS to boot completion
 * Understanding of SysVinit and systemd
 * Awareness of Upstart
 * Check boot events in the log file
 * The following is a partial list of the used files, terms and utilities:
 * dmesg
 * BIOS
 * bootloader
 * kernel
 * initramfs
 * init
 * SysVinit
 * system

Readings

 * 1)  Linux startup process
 * 2)  BIOS
 * 3)  Booting
 * 4)  GNU GRUB
 * 5)  Kernel (operating system)
 * 6)  Upstart (software)
 * 7)  dmesg
 * 8)  Initial ramdisk
 * 9)  init

Multimedia

 * 1) YouTube: Common Boot Loader Commands
 * 2) YouTube: Understanding the Linux Boot Process
 * 3) YouTube: An Overview of the Linux Boot Log Files

Activities

 * 1) Complete the tutorial IBM: Learn Linux, 101: Boot the system
 * 2) Use the GRUB boot menu.
 * 3) * Access the GRUB menu. Review available options and advanced options.
 * 4) * Edit one of the GRUB menu items to see the configuration but do not make any changes.
 * 5) * Access the command line. Use the  command to reboot the system.
 * 6) * Review Ubuntu: RecoveryMode. Boot into Recovery mode and review available options. Reboot the system.
 * 7) List the steps in the boot sequence from BIOS to boot completion.
 * 8) Identify which major Linux distributions use or used init, SysVInit, systemd, and Upstart.
 * 9) Compare the contents of   with the output from.

Lesson Summary

 * The boot sequence includes ROM, Power-On Self-Test (POST), boot manager, boot loader, and user software or graphical user interface (GUI).
 * A master boot record (MBR) is a special type of boot sector at the very beginning of partitioned computer mass storage devices like fixed disks or removable drives intended for use with IBM PC-compatible systems and beyond.
 * Boot loaders interact with the BIOS to load the operating system.
 * System V SysVinit startup is based on runlevels. SysVinit runlevels include:
 * 0 - Shutdown
 * 1 - Single-user mode
 * 2 - Multi-user mode
 * 3 - Multi-user mode with RFS
 * 4 - Multi-user mode, User-definable
 * 5 - Halt
 * 6 - Reboot
 * S - Single-user mode with terminal console
 * Upstart is an event-based replacement for the traditional init daemon.
 * Upstart was the default init system in Ubuntu and Chrome OS.
 * systemd is now the default init system in most Linux distributions, including RHEL and Ubuntu.
 * GRUB boot options include a list of operating systems, "e" to edit the list, and "c" for a command-line.
 * GRUB recovery mode provides a Recovery Menu of options.
 * dmesg (display message or driver message) is a command on most Unix-like operating systems that prints the message buffer of the kernel.

Key Terms

 * ELILO (EFI Linux Loader
 * EFI/UEFI boot loader


 * GRUB (GRand Unified Bootloader)
 * A boot loader package from the GNU Project.


 * initramfs (initial RAM file system)
 * A scheme for loading a temporary root file system into memory.


 * initrd (initial ramdisk)
 * A scheme for loading a temporary root file system into memory.