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Linux Directory Structure: Know Where Everything Is

Linux has a standard directory structure. Same on every system. Once you learn it, you'll never get lost.

This is the Filesystem Hierarchy Standard (FHS). It's boring. But essential.

The Root Directory (/)​

Everything starts at /. That's root. Not to be confused with the root user. Just the root of the filesystem.

/ (root)
├── bin/          # Essential commands
├── boot/         # Boot files
├── dev/           # Devices
├── etc/           # Configuration
├── home/          # User directories
├── lib/            # Libraries
├── media/          # Removable media
├── mnt/            # Temporary mounts
├── opt/            # Optional software
├── proc/            # Process info
├── root/            # Root user's home
├── run/              # Runtime data
├── sbin/             # System admin commands
├── srv/               # Service data
├── tmp/                # Temporary files
├── usr/                 # User programs
└── var/                  # Variable data

That's the structure. Learn it. You'll use it constantly.

The Directories You'll Actually Use​

/bin - Essential Commands​

Where basic commands live. ls, cp, mv, rm, cat, grep. The stuff that has to work even when everything else is broken.

Why it matters: These commands are always available. Even in single-user mode.

Real example:

$ ls /bin
bash  cat  cp  grep  ls  mv  rm  ...

/sbin - System Admin Commands​

Like /bin, but for system administration. Usually need root.

Contains: ifconfig, fdisk, systemctl, iptables. Admin stuff.

Real example:

$ ls /sbin
fdisk  ifconfig  init  systemctl  ...

/etc - Configuration Files​

This is where configuration lives. Everything that configures the system.

Important files:

  • /etc/passwd - User accounts
  • /etc/group - Groups
  • /etc/hosts - Hostname resolution
  • /etc/fstab - Filesystem mounts
  • /etc/ssh/sshd_config - SSH configuration
  • /etc/nginx/nginx.conf - Nginx config (if installed)

My take: You'll spend a lot of time in /etc. This is where you configure things.

Real example:

$ ls /etc
passwd  group  hosts  fstab  ssh  nginx  ...

/home - User Directories​

Where users live. Each user has a directory here.

Structure:

/home/
├── user1/
├── user2/
└── ubuntu/

My take: This is where you put your stuff. Your files. Your projects. Your life.

Real example:

$ ls /home
ubuntu  user1  user2
$ cd ~
$ pwd
/home/ubuntu

The ~ is shorthand for your home directory. You'll use it constantly.

/root - Root User's Home​

Like /home, but for the root user. Don't put your stuff here.

My take: Only root should use this. Regular users use /home.

/usr - User Programs​

Where most programs live. Not user programs in the sense of "for users," but programs that aren't essential for booting.

Structure:

  • /usr/bin - User commands
  • /usr/sbin - User admin commands
  • /usr/lib - Libraries
  • /usr/share - Shared data
  • /usr/local - Locally installed software

My take: Most of what you install goes here. Or in /usr/local if you install manually.

/var - Variable Data​

Data that changes. Logs. Spool files. Cache. Stuff that grows and shrinks.

Important:

  • /var/log - Log files (you'll be here a lot)
  • /var/spool - Spool files
  • /var/cache - Cache
  • /var/tmp - Temporary files

My take: /var/log is where problems hide. And where solutions live. Learn to read logs.

Real example:

$ ls /var/log
syslog  auth.log  nginx  apache2  ...

/tmp - Temporary Files​

Temporary files. Usually cleared on reboot. Don't put important stuff here.

My take: Use it for temporary work. Don't rely on it persisting.

/opt - Optional Software​

Third-party software. Stuff that doesn't fit the standard structure.

My take: Some software installs here. Docker. Some IDEs. Not everything, but some things.

/proc - Process Information​

Virtual filesystem. Shows running processes. Not real files - just information about the system.

My take: You'll rarely edit things here. But you'll read from it. cat /proc/cpuinfo to see CPU info. cat /proc/meminfo for memory.

Real example:

$ cat /proc/cpuinfo
processor	: 0
vendor_id	: GenuineIntel
...

/dev - Devices​

Device files. Everything is a file in Linux. Even devices.

My take: You'll rarely touch this directly. But it's good to know it exists.

/boot - Boot Files​

Kernel. Bootloader. Stuff needed to boot.

My take: Don't mess with this unless you know what you're doing. Breaking this breaks booting.

/media and /mnt - Mount Points​

Where you mount things. /media for removable media. /mnt for temporary mounts.

My take: You'll use /mnt for temporary mounts. /media is usually automatic.

The Mental Map​

Here's how I think about it:

  • /etc = Configuration (where you configure)
  • /home = Your stuff (where you work)
  • /var/log = Logs (where problems hide)
  • /usr = Programs (where software lives)
  • /tmp = Temporary (where temporary stuff goes)
  • /opt = Optional (where some software goes)

That's 90% of what you need to know.

Common Paths You'll Use​

/etc/nginx/nginx.conf          # Nginx config
/etc/ssh/sshd_config           # SSH config
/var/log/syslog               # System log
/var/log/nginx/access.log     # Nginx access log
/home/ubuntu/projects          # Your projects
/usr/local/bin                 # Local binaries

Learn these. You'll use them constantly.

What's Next?​

Now that you understand the directory structure, let's talk about File Permissions. We'll cover who can do what. It's important.

Or explore the directories. Actually go into them. See what's there. That's how you learn.

Personal note: When I started, I got lost constantly. I'd be in /etc and not know how I got there. That's fine. Use pwd to see where you are. Use cd ~ to go home. You'll learn the structure by using it.