Linux Internals Study Guide¶

Welcome to the comprehensive Linux Internals Study Guide, specifically designed for Linux internals interviews.

Overview¶

This documentation provides an in-depth exploration of Linux internals, covering everything from system calls and kernel mechanisms to networking protocols and performance troubleshooting. The material is structured to help you prepare for the rigorous technical interviews required for Google SRE positions.

Interview Focus

Google SRE Systems Engineering interviews focus heavily on Linux internals (more than coding). The Linux internals interview can go as deep as the interviewer wants - there's no limit. Be prepared to go from high-level concepts down to kernel implementation details.

What's Inside¶

Core Concepts¶

Deep dive into the fundamental building blocks of Linux systems:

System Calls & Kernel Internals - Understanding the transition between user space and kernel space
File System - Inodes, dentries, VFS, and journaling mechanisms
Memory Management - Virtual memory, paging, allocation strategies, and the MMU
Process Management - Process lifecycle, scheduling, and context switching

Communication¶

Learn how processes and systems communicate:

Inter-Process Communication (IPC) - Pipes, signals, sockets, and shared memory
Synchronization - Mutexes, semaphores, deadlocks, and race conditions
File Descriptors & I/O - Understanding file descriptor tables and I/O multiplexing

Networking¶

Master network protocols and the Linux network stack:

Network Fundamentals - OSI model, routing, switching, and VLANs
Protocols - TCP/UDP deep dives, DNS, DHCP, ARP, and NAT
Network Stack - Kernel network implementation and socket API

System Operations¶

Practical knowledge for system administration and troubleshooting:

Boot Process - Complete flow from BIOS to userspace
Performance Tools - Mastering top, vmstat, iostat, strace, and more
Troubleshooting - Systematic approaches to solving real-world issues

Interview Preparation¶

Strategies and resources for success:

Common Questions - Frequently asked "what happens when..." questions
Scenarios - Practice troubleshooting real-world problems
Tips & Strategies - Advice from successful candidates
Resources - Essential books and online materials

Key Interview Themes¶

Throughout your preparation, focus on these recurring question patterns:

"What happens when..." Questions¶

Interviewers love to ask about the complete flow of operations:

What happens when you type a command in the terminal?
What happens when you fork a process?
What happens when malloc() is called?
What happens when you type www.google.com in your browser?

Troubleshooting Scenarios¶

You'll be presented with symptoms and asked to systematically find the root cause:

High CPU usage investigation
Memory leaks and swap issues
Network connectivity problems
Performance degradation analysis

Deep Dives¶

Expect interviewers to keep asking "why" and "how" to test your depth of knowledge:

Start with high-level explanations
Be ready to drill down to kernel implementation details
Understand not just what happens, but why it works that way

Study Approach¶

Recommended Study Method

Start with fundamentals - Build a solid foundation in core concepts
Understand the "why" - Don't just memorize facts; understand why things work the way they do
Practice troubleshooting - Work through real scenarios systematically
Use the tools - Get hands-on experience with performance and debugging tools
Read the books - Especially "The Linux Programming Interface" by Michael Kerrisk

Use the navigation menu to explore different topics. Each section contains:

Detailed explanations of concepts
Code examples and diagrams
Common interview questions
Practical exercises
References to additional resources

Prerequisites¶

This guide assumes you have:

Basic Linux command-line experience
Understanding of C programming
Familiarity with basic operating system concepts
Access to a Linux environment for hands-on practice

Getting Started¶

If you're preparing for an interview, we recommend following this path:

Start with Core Concepts to build your foundation
Move to Communication to understand IPC mechanisms
Study Networking thoroughly (this is heavily tested)
Practice with System Operations tools
Review Interview Preparation materials before your interview

Interview Success Tips

Externalize your thinking - Always explain your thought process out loud
Ask clarifying questions - Don't assume; verify requirements
Be systematic - Use a structured approach to problem-solving
Admit when you don't know - It's okay to say "I'm not certain, but here's my reasoning..."

Good luck with your preparation!