Linux Filesystem Hierarchy & Inodes ('Everything is a File')

Lab 03 of 20 · Filesystem & Inodes · 5 hands-on activities · bilingual (English + සිංහල)

පිටුව 03: Linux Filesystem ගස, Inodes සහ Hard Links vs Soft Links

Linux හි 'හැමදේම File එකක්' කියන්නේ ඇයි? /etc, /var, /proc, /sys ව්‍යුහය, Inodes ක්‍රියාත්මක වන හැටි සහ Inode Exhaustion ප්‍රශ්නය විසඳමු.

Architectural Foundation & Systems Diagram

In Unix and Linux, a core design philosophy is: "Everything is a file". Hardware devices, processes, network sockets, and directories are all represented as file abstractions in the Virtual File System (VFS).

• 🌳 Root Filesystem Hierarchy — • /bin, /usr/bin: Essential executables.
  • /etc: System configuration files.
  • /var/log: Dynamic runtime logs.
  • /proc & /sys: Virtual in-memory kernel telemetry!

• 📑 What is an Inode? — An Inode (Index Node) is a data structure on disk storing file metadata: size, owner, permissions, timestamps, and disk block pointers. Crucially, the file's name is NOT stored in the inode!

• 🔗 Hard Links vs Soft Links — A Hard Link points to the exact same Inode number on disk. A Soft/Symbolic Link (Symlink) is a special shortcut file containing the pathname string of another target file.

Step-by-step practical lab

Step 01: Print Current Working Directory Path

සිංහලෙන් — අපි Terminal එකේ මේ මොහොතේ ඉන්න directory එකේ සම්පූර්ණ path එක පරීක්ෂා කරමු.

Print the absolute pathname of the current working directory to confirm your exact filesystem location.

pwd

• pwd : Print Working Directory: Root (/) සිට සම්පූර්ණ absolute path එක පෙන්වයි.

Expected output

/home/sre-engineer

Step 02: List Directory Files with Permissions & Inodes

සිංහලෙන් — Files වල සම්පූර්ණ විස්තර, permissions සහ hidden files බලාගනිමු.

List directory contents in long format, showing file permissions, owner, group, size in bytes, modification timestamp, and hidden dotfiles.

ls -la

• -l : Long listing format: Permissions, hard links, owner, group, size පෙන්වයි.
• -a : All: තිතෙන් (.) ආරම්භ වන සැඟවුණු hidden files (.bashrc, .profile) ද පෙන්වයි.

Expected output

drwxr-xr-x 6 sre-engineer devops  4096 Sep 16 12:40 .
drwxr-xr-x 3 root         root    4096 Sep 16 09:12 ..
-rw-r--r-- 1 sre-engineer devops  1420 Sep 16 11:15 Dockerfile

Step 03: Filter Configuration Lines Using Regular Expressions

සිංහලෙන් — Files තුළ ඇති වැදගත් දත්ත සොයාගැනීමට Grep command එක භාවිත කරමු.

Search text files or stream inputs for matching string patterns and display matching lines.

grep -i 'listen' configs/nginx.conf

• -i : Ignore case: Capital/simple අකුරු භේදයකින් තොරව සෙවීම සිදු කරයි.

Expected output

    listen 80 default_server;
    listen [::]:80 default_server;

Hands-on practice activities

Work through these yourself — tick them off as you go.

• Activity 11: Print Working Directory Location (Drill) — Print the absolute pathname of the current working directory to confirm your exact filesystem location.
• Activity 12: Inspect Inode Metadata Numbers (Drill) — Use the -i flag with ls to print the unique numeric filesystem Inode index assigned to /etc/hosts.
• Activity 13: Audit Filesystem Inode Capacity (Drill) — Verify Inode usage percentages across all mounted partitions to catch runaway inode exhaustion before outages occur.
• Activity 14: Understand /proc Virtual Filesystem (Checkpoint) — /proc does NOT exist on your hard drive! It is generated dynamically by the Linux kernel in RAM to expose runtime statistics.
• Activity 15: File Name Location Quiz (Quiz) — Is the filename of a file stored inside its inode data structure? Answer: No, it is stored in directory entries mapping to the inode.

Keep going: ← Lab 02 · Lab 04 → · Track your progress in the Self Guide