Understanding Files and File System: Files and Directories in Linux
1. Introduction
In Linux, everything is treated as a file—documents, directories, devices, and even running processes. The Linux file system provides a structured way to store, organize, and manage data using files and directories.
Understanding files and directories is fundamental for Linux usage, system administration, and exams.
2. What is a File in Linux?
A file is a collection of data stored on disk with a name and attributes.
Types of Files in Linux
Linux supports multiple file types:
| File Type | Description | Symbol |
|---|---|---|
| Regular file | Text, binary, scripts | - |
| Directory | Contains files | d |
| Character device | Keyboard, mouse | c |
| Block device | Hard disk | b |
| Symbolic link | Shortcut to file | l |
| Socket | Network communication | s |
| FIFO (pipe) | Inter-process communication | p |
📌 Command to view file type:
ls -l
3. File Attributes
Each file in Linux has attributes:
- File name
- File type
- Permissions (read, write, execute)
- Owner and group
- Size
- Time stamps (created, modified, accessed)
Example:
-rw-r--r-- 1 user group 1024 file.txt
4. What is a Directory?
A directory is a special type of file that stores names and locations of other files.
Directories help in:
- Organizing files
- Creating a hierarchical structure
- Efficient file management
5. Linux Directory Structure (File System Hierarchy)
Linux follows a single-rooted, tree-like structure starting from / (root directory).
Important Directories
| Directory | Purpose |
|---|---|
/ | Root directory |
/bin | Essential commands |
/sbin | System admin commands |
/etc | Configuration files |
/home | User home directories |
/root | Root user’s home |
/var | Variable data (logs) |
/tmp | Temporary files |
/dev | Device files |
/proc | Process information |
/usr | User applications |
6. Understanding Paths
Absolute Path
- Starts from root
/ - Example:
/home/user/file.txt
Relative Path
- Starts from current directory
- Example:
../file.txt
7. File and Directory Permissions
Linux uses permission-based security.
Permission Types
r– Readw– Writex– Execute
Permission Levels
- Owner
- Group
- Others
Example:
-rwxr-xr--
8. Common File & Directory Commands
File Commands
touch file.txt
cat file.txt
rm file.txt
cp file1 file2
mv old new
Directory Commands
mkdir folder
rmdir folder
cd folder
ls
9. Links in Linux
Hard Link
- Points to same inode
- Cannot link directories
- Survives file deletion
Symbolic Link
- Points to file path
- Can link directories
- Broken if original deleted
Command:
ln file1 file2 # hard link
ln -s file1 link1 # soft link
10. File System in Linux
The file system defines how files are:
- Stored
- Organized
- Retrieved
Common Linux File Systems
- ext4 (most common)
- XFS
- Btrfs
- FAT, NTFS (supported)
11. Mounting File Systems
Linux uses mount points to access file systems.
Example:
mount /dev/sda1 /mnt
12. Special Files Concept
/dev→ hardware as files/proc→ running processes as files/sys→ kernel info
📌 Reinforces: Everything is a file
13. Advantages of Linux File System
- Strong security
- Organized hierarchy
- Supports large file sizes
- Highly stable and efficient
14. Conclusion
Linux treats files and directories as core building blocks of the operating system. Its hierarchical file system structure, strong permissions, and flexible file handling make Linux secure, powerful, and efficient, especially for servers and multi-user environments.