Systems

Notes on Linux systems administration, kernel internals, and system-level concepts.

Core Topics

System Fundamentals

• Linux Kernel Boot Process
• Common Files and Directories
• Devices
• Disks
• File Systems
• Groups
• Hard and Soft Links
• LVM (Logical Volume Manager)
• Memory Management — virtual memory, address space layout, stack/heap, free space management, paging, virtual address structure (VPN/offset), address translation, page table entry flags, TLB, linear and multi-level page table structures, x86-64 four-level page table, Linux physical memory (NUMA/UMA, nodes, zones)
• Networking
• Network Manager
• Permissions
• Processes
• Storage
• Time
• Users and User Management

System Services and Configuration

• Systemd
• PAM (Pluggable Authentication Modules)
• Logging
• Scheduled Tasks
• Bash Startup Files

Development and Tools

• Development Tools
• Make
• Linux Commands

System Internals

• Kernel
• Interrupts
• System Calls — user/kernel mode, trap mechanism, IDT, syscall numbers, C library wrappers, process states, fork/exec/exit/wait/waitpid, file I/O (open/read/write/close), signals (kill/sigaction), memory (brk/mmap)
• Process Scheduling

Observability and Troubleshooting

• Observability Sources
• Per-Process Analysis
• System-Wide Analysis
• Troubleshooting

Subdirectories

Bash

Shell scripting and bash-specific notes

• Bash Notes
• Keyboard Shortcuts

Commands

Detailed documentation for specific Linux commands

• chgrp
• chmod
• chown
• dd
• groups
• ip
• Job Control
• kill
• lsscsi
• passwd
• ps
• umask

Greybeard Qualification

Advanced Linux system administration topics

• Block Devices and File Systems
• Memory Management
• Process Execution and Scheduling
• Process Structure and IPC
• Startup and Init