1.3 Partitioning and Boot Process

Storage Basics

The Filesystem Hierarchy Standard (FHS)

Linux organizes files in a tree structure, not drive letters (C:, D:). Everything starts at / (root).

Path	Purpose
/	Root. The top of the hierarchy.
/boot	Kernel (vmlinuz), initramfs, and bootloader config.
/etc	Configuration files.
/home	User data (e.g., /home/alice).
/root	Home directory for the root user.
/var	Variable data: logs, databases, websites (/var/www).
/tmp	Temporary files (often cleared on reboot).
/bin, /usr/bin	Binaries (programs) like ls, cp.

Partitioning Schemes

MBR (Master Boot Record)

• Legacy.
• Max 4 primary partitions.
• Max 2TB disk size.

GPT (GUID Partition Table)

• Modern standard (part of UEFI spec).
• Practically unlimited partitions.
• Supports massive disks (Zettabytes).

Recommended Partition Layout:

Tip

1. EFI System Partition (100-500MB): FAT32. Needed for UEFI boot.
2. /boot (1GB): Ext4/XFS.
3. swap: Virtual memory. (Rule of thumb: 1x-2x RAM, though less critical with modern massive RAM).
4. / (Root): The rest of the disk (often managing /home and /var inside it, or separating them for safety).

The Boot Process

How do we get from power button to login prompt?

graph TD
    A[BIOS / UEFI] -->|POST & Hardware Init| B[Bootloader (GRUB2)]
    B -->|Selects OS| C[Kernel]
    C -->|Mounts Initramfs| D[Initramfs (Temporary Root)]
    D -->|Loads Drivers| E[Real Root Filesystem Mounted]
    E -->|Starts Init Process| F[systemd (PID 1)]
    F -->|Parallel Execution| G[Targets & Services]
    G --> H[Login Prompt]

1. BIOS/UEFI: Firmware initializes hardware and looks for the boot device.
2. GRUB2 (Grand Unified Bootloader): Detailed menu to select the Kernel. Loads the Kernel into memory.
3. Kernel: The core OS. It initializes hardware drivers.
4. Initramfs: A small temporary filesystem loaded into RAM. It helps the kernel fix mounting the real hard drive (e.g., loading decryption keys or specialized drivers).
5. Init (Systemd): The first process (PID 1). It reads configuration files and starts all other services (Network, SSH, Web Server) in parallel.

Related Concepts: Disks and Partitions Learn more about handling disks in Module 4.