Linux File System Hierarchy — Directories, Files, and Links

Overview

Linux presents all storage — local disks, network shares, removable media, virtual filesystems, and device nodes — as a single directory tree rooted at /. There is no concept of drive letters. Everything is a path. The Filesystem Hierarchy Standard (FHS) defines where different categories of files belong so that administrators and software can find things predictably across distributions. Knowing the purpose of each major directory, how to navigate the tree efficiently, and how links and glob patterns work is the baseline for all file system work in RHEL.

Filesystem Hierarchy Standard

The RHEL 9 merger of /bin → /usr/bin and /sbin → /usr/sbin (implemented as symlinks) simplifies the hierarchy: all system executables now live under /usr, making it easier to snapshot and restore a read-only /usr partition independently of /.

Absolute and Relative Paths

Every file on a Linux system can be described by an absolute path or a relative path.

An absolute path starts with / and fully describes the file’s location from the root of the tree. It is unambiguous regardless of where you are in the filesystem:

/etc/ssh/sshd_config
/home/student/documents/report.txt

A relative path describes the file’s location relative to the current working directory. It does not start with /. Two special directory entries appear in every directory:

• . refers to the current directory itself
• .. refers to the parent directory

../config          # one level up, then into config/
documents/report   # subdirectory of the current directory
./script.sh        # script in the current directory

Relative paths are shorter to type for nearby files; absolute paths are required in configuration files and scripts where the current directory is unpredictable.

Navigating the Filesystem

File and Directory Operations

The rm -rf combination (recursive and force) is the most dangerous command a new administrator will use. It deletes directories and all their contents without confirmation and cannot be undone. Always verify the path before pressing Enter, especially when running as root.

Hard Links and Symbolic Links

Linux filesystems use inodes to store file metadata (permissions, ownership, timestamps, pointers to data blocks). A directory entry is simply a name-to-inode mapping. This architecture allows multiple names to point to the same inode.

Hard Links

A hard link is a second directory entry that points to an existing inode. Both names are equal peers — neither is the “original.” The inode tracks how many directory entries reference it (the link count). The file’s data is not deleted until the link count reaches zero.

ln existing_file hardlink_name

Constraints on hard links:

• Cannot cross filesystem boundaries (both names must be on the same mounted filesystem)
• Cannot link to a directory (prevents circular references)
• Deleting one name does not affect the other; ls -l shows the link count > 1 while hard links exist

Symbolic Links

A symbolic link (soft link) is a special file that contains a path to another file or directory. The kernel follows the path stored in the symlink to reach the target.

ln -s /etc/nginx/nginx.conf nginx.conf

ls -l shows symbolic links with l in the permissions field and an arrow indicating the target:

lrwxrwxrwx. 1 root root 20 Jan 10 09:00 nginx.conf -> /etc/nginx/nginx.conf

Symbolic links are more common in practice because they can span filesystems and link directories, making them essential for configuration management (linking versioned config files), /usr/bin wrappers, and shared libraries.

Glob Patterns

The shell expands glob patterns to matching filenames before passing them to commands. This expansion happens in the shell, not inside the command — ls *.log passes the list of matching filenames to ls, not the literal string *.log.

Brace expansion looks similar but is distinct — it expands to a list of strings without checking whether files exist:

Practical examples:

ls /var/log/*.log         # All .log files in /var/log/
rm cache_?.tmp            # Files like cache_1.tmp, cache_a.tmp
cp /etc/[abc]* /backup/   # Files starting with a, b, or c
touch report_{jan,feb,mar}.txt   # Create three files with brace expansion

If no files match a glob pattern, Bash passes the literal unexpanded pattern to the command by default — which usually causes an error. The nullglob shell option changes this behaviour to pass an empty list instead.

Summary

The Linux filesystem tree is rooted at /, with each major directory serving a defined purpose: /etc for configuration, /var for variable runtime data, /usr for installed software, and virtual filesystems like /proc and /sys for kernel introspection. Absolute paths start at /; relative paths start from the current directory using . and ... Hard links give a file multiple names within the same filesystem; symbolic links point to paths and can cross filesystem boundaries. Glob patterns are expanded by the shell before the command runs, allowing wildcard selection of files without the command needing to implement its own matching logic.