Linux file system layout explained: home, etc, var and more

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Open a file manager on Linux and click on the top level of the drive, and you will see a set of short, cryptic folder names. There are no drive letters, no Program Files and no Users folder. The layout follows a long-standing convention called the Filesystem Hierarchy Standard, and once you know what each folder is for, the whole system makes more sense.

One tree, starting at root

Everything on a Linux system sits in one tree that starts at a single slash, called the root directory. Other drives and USB sticks do not get letters; they are attached, or mounted, at a folder somewhere in that tree. Paths use forward slashes, and names are case sensitive, so a file called Notes and one called notes are different files.

Where your own files live

/home contains a folder for each user, such as /home/alex. This is your space: documents, downloads, pictures and your personal settings. The shortcut ~ in the terminal means your home folder.
Hidden files and folders in your home begin with a dot. Many programs keep settings there, for example in a .config folder. File managers hide them by default; a keyboard shortcut, often Ctrl+H, shows them.
/root is the home folder of the root administrator account, separate from /home.

If you back up only one folder, it is your home folder.

Programs and libraries

/usr holds most installed software and its supporting files. Programs are usually in /usr/bin, libraries in /usr/lib and shared data such as icons and documentation in /usr/share.
/usr/local is the conventional place for software you install yourself outside the package manager.
/bin and /sbin traditionally held essential commands. On many modern distributions they are simply links into /usr.
/opt is used by some third-party software that installs as a self-contained bundle.

Leave /usr to the package manager. Editing or deleting files there by hand is a good way to break updates.

Configuration

/etc holds system-wide configuration files, mostly plain text. Examples include the list of file systems to mount at start-up, network settings and settings for services.
Back up a file before editing it, for example by copying it with an extra .bak ending, and edit with administrator rights only when you understand the change.
Your personal settings override many system defaults and live in your home folder instead.

Data that changes

/var contains variable data that grows and changes while the system runs: logs in /var/log, package caches, mail spools, databases and websites on servers. If the disk fills up unexpectedly, /var is a common place to look.
/tmp is for temporary files. Many distributions clear it at each restart, so never keep anything important there.

Hardware and the running system

/dev contains device files representing hardware such as disks, for example /dev/sda or /dev/nvme0n1. Treat these with great care; writing to the wrong device can wipe a drive.
/proc and /sys are virtual file systems created in memory by the kernel. They show information about running processes and hardware rather than files stored on disk.
/run holds runtime information since the last boot.

Boot and mounting

/boot contains the kernel and the files needed to start the system. On UEFI computers, the EFI System Partition is often mounted at /boot/efi.
/mnt is a conventional place to mount a file system temporarily by hand.
/media is where many desktops automatically mount USB sticks and external drives, often in a folder named after your user.

Libraries and other folders

/lib traditionally held libraries needed by essential programs, and on many systems is now a link into /usr/lib.
/srv is sometimes used for data served by the system, such as website files, though conventions vary.
lost+found appears at the top of some file systems and holds file fragments recovered after a disk check.

Practical tips

Work inside your home folder for everyday files.
Use the package manager rather than copying files into system folders.
Check disk usage by folder with the 'du' and 'df' commands or a graphical disk usage analyser when space runs low.
Read the hier manual page, by typing 'man hier' in a terminal, for your system's own description of the layout.

Which Linux folder confused you most when you started? Share it in the comments.