Filesystem

Core Idea

A filesystem organizes persistent data into directories, files, metadata, and permissions.

What You See As A User

pwd
ls -la
stat ~/src/pages/index.md
find ~ -maxdepth 2 -type f

Paths are names. Files have content. Directories contain names. Metadata includes owner, group, permissions, size, timestamps, and type.

Important Path Ideas

• /: filesystem root.
• ~: your home directory.
• .: current directory.
• ..: parent directory.
• Absolute path: starts with /.
• Relative path: starts from the current directory.

Filesystem Metadata

ls -l gives a compact view. stat gives a detailed view.

stat ~/src/pages/index.md

Look for file type, size, owner, group, permissions, and timestamps.

Mounts And Virtual Filesystems

Some filesystem paths are not ordinary disk files. /proc exposes process and kernel information. /dev/null is a special device that discards bytes. These are still accessed through filesystem paths.

Common Confusions

• A directory is not just a visual folder; it maps names to entries.
• Deleting a filename is not the same mental model as erasing every byte immediately.
• ~/src/pages/index.md and ~/public_html/index.html are different files with different roles.
• Editing generated output is fragile; edit source and rebuild.

Proof Check

Run stat ~/src/pages/index.md and identify owner, permissions, size, and modification time.

Docs Pointers

• Run man hier, man stat, man find, and man 7 inode.
• Read Filesystem Navigation for beginner movement commands.
• Read Path, File, and Directory for the objects you manipulate every session.
• Read Permissions and Number Bases: Decimal, Hexadecimal, Octal for permission metadata.
• Read [Devices And /dev](/docs/concepts/devices.md/) for special filesystem paths under /dev`.