Table of Contents
Understanding the Root Filesystem
The root filesystem is the starting point of everything you see in a running Linux system. It is represented by the single forward slash /. Every file and every directory you will ever use lives somewhere under this root. There are no separate drive letters as in some other operating systems. Instead, all storage is attached to this one tree.
When you see a path like /home/alex/Documents, it means you start at the root /, then go into the home directory, then into the alex directory, and finally into Documents. The root filesystem is the top of this tree.
The root directory / is the absolute starting point of the Linux filesystem. Every path on the system ultimately begins at /.
Directories vs Filesystems
It is important to distinguish between directories and filesystems. A directory is simply a place that can contain files and other directories. A filesystem is a structure on some storage device that can store directories and files.
Linux can attach, or mount, a filesystem at any directory. For example, you might have your main filesystem on one disk and a separate filesystem for user data on another disk. The second filesystem can be mounted at /home. From the user’s point of view, there is just the directory /home, but behind the scenes it might be a different filesystem on a different device.
The root filesystem is the first filesystem mounted when the system starts. Other filesystems are attached under it, but everything still appears under the same tree that begins at /.
System-Wide Organization
Because everything shares a single tree, Linux relies heavily on a standard layout under the root directory. Different types of data are expected to live in different places. For example, configuration files are in one area, user files in another, and temporary files in yet another.
This structure is not random. It follows conventions documented in the Filesystem Hierarchy Standard (FHS). Not all distributions follow the standard perfectly, but most of them are very similar in how they organize things. The result is that once you learn what lives where under /, you can find your way around almost any Linux system.
At the top level, the root filesystem contains directories such as /home, /etc, /var, /usr, /tmp, /dev, /proc, and /sys. Each of these has a specific purpose that you will explore in detail in later sections.
Paths and the Root
Every location in the system can be described by its path. A path that starts with / is called an absolute path, because it always begins from the root. For example, /etc/passwd is the full address of a file that stores basic user account information.
If a path does not start with /, it is interpreted relative to the current directory, not from the root. For instance, if your current directory is /home/alex, the path Documents/report.txt refers to /home/alex/Documents/report.txt. The absolute version starts from /, while the relative version starts from wherever you are.
The root directory / itself is a special case. Its path is just /. It has no parent directory above it. If you go “up” from /, you stay at /.
Any absolute path in Linux begins at /. If you see a path that does not start with /, it is relative to your current location.
The Root User vs the Root Directory
Beginners are often confused by the word “root”, because it can refer to both the root directory / and the root user account. They are related only by name.
The root directory is the top of the filesystem. The root user is a special administrator account with full control over the system. The root user’s home directory is usually /root, which is simply a directory named root that lives directly under /, like any other top-level directory.
When you see / by itself, it usually means the root directory. When you see /root, it refers to the home directory of the root user. Understanding this distinction will help you avoid confusion as you work with the filesystem.
Devices Within the Root Tree
One of the more unusual aspects of Linux is how it represents hardware inside the root filesystem. Instead of treating devices as something completely separate, Linux exposes them as special files, mostly under /dev. These entries are not regular files that you can read like text, but they still live inside the same directory tree that starts at /.
Similarly, /proc and /sys provide views into the running system and the kernel. They look like normal directories and files inside the root filesystem, but many of them are generated on the fly by the system rather than stored on disk.
All of these locations are still part of what you see when you explore from /. Even though they work differently from normal files on a disk, they are integrated into the same hierarchy.
Root Filesystem and Multiple Disks
A Linux system can use several storage devices, but it still presents a single unified tree. The root filesystem might live on one partition of one disk, while other partitions or disks hold additional filesystems that are mounted somewhere under /.
For example, your system might have:
- A root filesystem on one partition, containing directories like
/etc,/var, and/usr. - A separate filesystem on another partition, mounted at
/home.
From the user’s perspective, /home is just another directory under /. You do not have to think about which physical device it is on when you navigate. The kernel and system tools handle the details.
This approach to storage is what allows Linux to keep a simple view of paths starting from /, even when the layout of disks and partitions is complex.
Why the Root Filesystem Matters
Understanding the root filesystem is essential to working comfortably with Linux. It influences how you interpret paths, how you think about storage, and how you find important files.
Since every key component of the system appears somewhere under /, you can always start from the root and work your way down to what you are looking for. As you learn what each top-level directory under / is meant to contain, you will be able to guess the location of files and tools even on systems you have never seen before.
In later sections you will look at the major directories that live directly under / and see what role each one plays in this larger structure.