person Tute World Team

Phase 2: Boot & Init

Every time you press the power button, a carefully orchestrated sequence runs — from the firmware waking up the CPU to the login prompt appearing. Understanding this sequence is fundamental to debugging startup failures, customizing boot behavior, and understanding how systemd controls your system.

What You'll Learn

1. Linux Boot Process

Step-by-step: power on → BIOS → GRUB → kernel → PID 1 → login.

2. GRUB Bootloader

How GRUB finds and loads the kernel, config format, kernel parameters.

3. Kernel Startup

What the kernel does before PID 1: hardware detection, memory setup.

4. initramfs

Why a temporary RAM filesystem is needed before mounting root.

5. systemd vs init

Architecture comparison: sequential SysV scripts vs parallel systemd.

6. systemd Units

Service, target, socket, timer units — anatomy and practical usage.

7. Boot Targets & Runlevels

systemd targets vs SysV runlevels, rescue and emergency modes.

8. journald

Binary logging, journalctl usage, log levels, persistence settings.