Linux Kernel Filesystem Development

How to develop a Linux kernel disk-based filesystem from scratch

What you'll learn

Understand the flow from Linux user processes through to the kernel VFS layer and the interaction between the kernel and the filesystem.

Learn how to build a loadable kernel module and supporting commands (mkfs & fsdb) and how to create additional files on disk during mkfs time.

Developing a disk-based filesystem from scratch by understanding the process to follow and the order in which operations should be implemented

You will cover how to mount/umount a filesystem as well as all file and directory operations on directories, reglar files, hard links and symlinks.

Understanding kernel debugging techniques from simple use of printk calls to source level debugging with gdb/KGDB.

Requirements

Linux/UNIX development, basic kernel knowledge, good working level of C

No need for assembler language or the ability to build a Linux kernel. You'll just need to install Ubuntu and development tools and compile the filesystem and commands

Description

This course will teach you how to develop a Linux kernel filesystem from scratch. You will learn everything from building the commands and kernel module, loading the module, mounting a filesystem, unmounting and removing the module. All basic file / filesystem operations are supported with a module for each operation. We’ll cover everything from file, directory, symlink and hard link creation to reading and writing files to details about filesystem / kernel interactions. There is also a chapter covering how to undelete a file which also highlights potential security issues. With the kernel module, mkfs and fsdb commands, the SPFS filesystem is only 2300 lines of code. The source code is accessible on-line and will be updated every year for new versions of Ubuntu Linux.You will learn the strategy to follow when building a new filesystem. What operations need to come first and which ones can wait until later.You will also learn how to debug the filesystem using a number of techniques from simple use of printk to source-level debugging using gdb/KGDB.The filesystem is very simple and contains intentional errors which help with understanding why the order of operations is very important during filesystem design.The course is supported by a free 450-page online Linux kernel filesystem book.

Overview

Section 1: Introduction

Lecture 1 Introduction

Section 2: How to get started

Lecture 2 How to get started

Section 3: SPFS — A Linux Filesystem For Teaching

Lecture 3 SPFS — A Linux Filesystem For Teaching

Section 4: Downloading the SPFS source code

Lecture 4 Downloading the SPFS source code

Section 5: The order of events when designing a filesystem

Lecture 5 The order of events when designing a filesystem

Section 6: Setting up your environment

Lecture 6 Setting up your Environment

Section 7: Loading / Unloading a Module

Lecture 7 Loading / Unloading a Module

Section 8: Mounting a Filesystem

Lecture 8 Mounting a Filesystem

Section 9: Pathname resolution - part 1

Lecture 9 Pathname resolution - part 1

Section 10: Pathname resolution - part 2

Lecture 10 Pathname resolution - part 2

Section 11: Putting it all together so far

Lecture 11 Putting it all together so far

Section 12: Creating a Regular File

Lecture 12 Creating a Regular File

Section 13: Creating Directories

Lecture 13 Creating Directories

Section 14: Reading Directory Entries

Lecture 14 Reading Directory Entries

Section 15: Reading From a File

Lecture 15 Reading From a File

Section 16: Writing to a File

Lecture 16 Writing to a File

Section 17: Hard Links and Symbolic Links

Lecture 17 Hard Links and Symbolic Links

Section 18: Inode Management

Lecture 18 Inode Management

Section 19: Removing a File or Directory

Lecture 19 Removing a File or Directory

Section 20: Renaming a File

Lecture 20 Renaming a File

Section 21: Obtaining Filesystem Information via statfs

Lecture 21 Obtaining Filesystem Information via statfs

Section 22: Unmounting a Filesystem and Removing the Module

Lecture 22 Unmounting a Filesystem and Removing the Module

Section 23: File Undelete

Lecture 23 File Undelete

Section 24: Conclusion — Where to go From Here?

Lecture 24 Conclusion — Where to go from here?

Experienced developers who wish to explore Linux kernel development, specifically in the area of filesystems