The Shell & Filesystem Hierarchy

What is it?

The shell (usually bash) is the text interface you type commands into; the filesystem is a single tree rooted at / with standard directories (/etc config, /var logs/data, /home users, /bin programs).

Why it matters

Knowing where things live is half of administration: config in /etc, logs in /var/log, user data in /home — you find and fix faster when the map is in your head.

Where you see it

`pwd` shows where you are, `ls` lists, `cd` moves, `cat`/`less` view files; absolute paths start at /, relative from the current directory.

What normal looks like

A predictable hierarchy: configs under /etc, service logs under /var/log, binaries under /usr/bin — the same on nearly every distribution.

What suspicious looks like

Config edited in the wrong place, a service writing to a full /var, or a file created under / by mistake — misplacement is a common source of 'it doesn't work'.

How analysts investigate

Anchor on the standard locations: to change behavior look in /etc, to see what happened look in /var/log, to find a user's files look in /home.

Common beginner mistakes

Confusing absolute (/etc/ssh) with relative (etc/ssh) paths.
Looking for logs or config outside their standard directories.

One tree, standard branches

  /
  ├─ etc/      configuration (sshd_config, fstab, crontab)
  ├─ var/log/  logs (syslog, auth.log)
  ├─ home/     user files (/home/j.rai)
  ├─ usr/bin/  programs
  └─ tmp/      scratch

The Linux filesystem is one tree from /; standard directories hold config, logs, users and programs.

Quick check

Where do you look to change a service's configuration?

A quick self-check — it doesn't affect your XP or progress.