1.4. Reflection Checkpoint

Before moving to Phase 2, confirm you can answer these questions from understanding — not memorization:

Core Architecture:

• What does "everything is a file" mean concretely? Give three examples of non-file things Linux represents as files.
• What is the role of the kernel vs. the GNU userspace tools? Why does this distinction matter for licensing?
• Why do user applications make system calls instead of accessing hardware directly?

Boot Process:

• In order: what are the four stages of a Linux boot, and what does each hand off to the next?
• Why does Linux need an initramfs? What problem does it solve?
• Where should you edit GRUB configuration, and why should you never edit grub.cfg directly?
• What is systemd's PID, and why is that significant?

Filesystem Hierarchy:

• What makes /proc different from every other filesystem on a Linux system?
• What is the difference between a block device and a character device? Give a real example of each.
• A script fails with "command not found" even though the binary exists at /usr/local/bin/myscript. What is the most likely cause?
• Why should applications use /var/tmp instead of /tmp for temporary files that must survive a reboot?

If you can answer all of these confidently, Phase 2 will feel like learning familiar tools rather than memorizing new concepts.