the Linux File System explained in 1,233 seconds // Linux for Hackers // EP 2

Linux’s file system is built on one unifying idea: practically everything—configuration, devices, even command programs—is represented as files arranged in a predictable directory hierarchy. That framing matters because it turns “where do I find this?” and “how do I change this?” into navigable, repeatable tasks instead of guesswork.

The session starts at the root of the file system (/), then uses basic terminal commands to orient the learner: whoami to identify the current user, ls to list directory contents, pwd to show the current path, cd to move between directories, and clear (or Ctrl+L) to tidy the terminal. From there, the lesson expands into the core claim: commands like ls aren’t magic—they live as binaries stored in directories and can be inspected like files. By navigating to /bin (the “binaries” directory), the learner finds essential command binaries, including ls. Running cat ls prints the contents of the ls binary to the terminal, demonstrating that the command is indeed a file.

To make the file analogy concrete, the lesson performs file operations on command binaries. It uses cp to copy the ls binary into a new file (named “network chuck”), then executes that new file as a command—showing that copied binaries remain runnable. It also uses rm to remove the original ls binary, requiring elevated privileges via sudo when permissions block the action. After deleting ls, listing the directory no longer works until the binary is restored by copying the modified file back to ls. The takeaway is practical: Linux permissions and file locations directly control what commands exist and what actions succeed.

The directory structure then gets mapped. /bin holds essential user-facing commands, while /sbin (often “super binaries”) contains administrator-focused commands. The lesson also highlights that /usr contains its own bin and sbin directories that largely mirror /bin and /sbin, with overlap and historical reasons tied to storage and system layout. The which command is introduced as a way to determine which copy of a command will run (e.g., whether ls comes from /bin or /usr/bin).

Next comes a tour of major system directories and what they’re for: /boot contains boot files needed to start the system; /var stores logs and web/application-related data; /tmp holds temporary files; /lib provides shared libraries; and /home is where user accounts live (with root handled separately). The root user’s files are accessible under /root, but require sudo to inspect. Device files appear under /dev, where hard drives are represented as vda/vda1 in this environment; attempting to cat a device illustrates how raw device data can overwhelm a terminal, so Ctrl-C is used to stop it.

Finally, configuration files live under /etc. The lesson drills into networking by reading /etc/network/interfaces with sudo cat interfaces, where IP addresses and interface settings are stored. The tour closes with /media and /mnt, both used for mounting drives—/media for automatic mounting of removable media, and /mnt for manual mounting workflows. The session ends with a command-memorization and practice “homework” plan, emphasizing that knowing where things live in the FHS makes troubleshooting, configuring, and hacking far faster.