#OS

I wasted 50% of my disk space because I didn't know the difference between Copy and Link. Deep dive into Inode, the secret of `rm` command, and why `pnpm` is faster than `npm`.

How OS creates the illusion of multitasking. Preemptive vs Non-preemptive, The Starvation problem, and how modern OSs use Multi-Level Feedback Queue (MLFQ) and Red-Black Trees (Linux CFS) to keep everyone happy.

Concurrency is about structure, Parallelism is about execution. Understanding Single-core multitasking vs Multi-core processing.

A deep dive into one of the oldest and most dangerous software vulnerabilities. How rewriting the Return Address works, and how modern OS protections like ASLR, DEP/NX, and Stack Canaries attempt to stop it.

Developers must use Mac? That was before WSL2. Planting Linux Kernel inside Windows.

What if Airbag deploys late due to Windows Update? It doesn't mean 'Fast'. It means 'Deterministic'.

Conductor of VMs. Is the CEO running it directly (Type 1), or hiring a manager (Type 2)?

Running Windows & Linux on my MacBook. Foundation of Cloud Computing (AWS).

What if pull the plug while copying files? OS's habit of logging to prevent corruption.

Filename is just a shell in Linux. The real identity is inode number. Secret of ls -i.

HDD is just a giant field of 0s and 1s. Magic that creates 'File' and 'Folder'.

PC froze. Mouse moves but clicks don't work. HDD led blinking like crazy. This is Thrashing.

Desk is full. Which book to throw away? Oldest? Least used? OS's decision making.

If Paging is mechanical chopping, Segmentation is meaningful organization. Managing by Code, Data, Stack.

Slice memory into identical grid blocks. The standard technique aiming to solve External Fragmentation.

Why does my server crash? OS's desperate struggle to manage limited memory. War against Fragmentation.

Processes are isolated. But how do Chrome tabs exchange data? From Pipes to Sockets.

Code is perfect, but money disappears occasionally. Worst bugs created by timing issues.

Understanding sync with Restroom Key (Mutex) and Waitlist (Semaphore). Ownership differences, Spinlocks, Monitors, and Priority Inversion (Mars Pathfinder).

Why processes freeze forever. From Dining Philosophers to Distributed Deadlock Detection. Includes Resource Allocation Graphs, Banker's Algorithm, and Java/DB examples.

Why is CPU switching expensive? Cache Pollution, TLB Flush, Kernel Mode, vmstat tuning, and deep dive into Linux Kernel's switch_to macro.

The definitive guide with Factory analogy. Chrome's Multi-process architecture, typical C code examples (fork vs pthread), and deep dive into Green Threads (Goroutines).

Not a Demon. It's the 'Guardian Spirit' from Greek mythology. Heroes of the server working silently in the background.

Senior dev said 'just chmod 777 it'. Turns out, that was reckless advice. Secrets of rwx and numbers.

iTerm2 is not a real terminal. It's an Emulator. From Teletype (TTY) relics to PTY.

Shell is not the core of OS. It's just a 'Messenger' passing user commands to Kernel. The real role of zsh and bash.

Developers can't control the hard disk directly. Instead, we must 'ask' the Kernel via an API. That request is the System Call.

When your code tries to enter Kernel Mode, CPU blocks it. Why split the computer into two modes?

If an OS is a collection of programs, who is the core? Identity of the Kernel that always stays in memory.

Without an OS, we'd have to calculate which sector of the hard drive to write 0s and 1s to. What Linux and Windows do for us.

When the CPU is 100% busy and you move the mouse, does it respond? Polling vs Interrupts explained.

How do you run a 10GB game with only 8GB of RAM? The OS secretly uses part of your hard drive.

What happens inside when you turn on a computer? A detailed breakdown of the 6 stages of Linux booting. Covering Dual Booting, Secure Boot, Kernel Modules, Systemd Unit Files, and troubleshooting with Journalctl.