demofs — A Linux Filesystem

demofs is a custom Linux filesystem module written in C. It provides a simple, educational filesystem implementation that integrates with the Linux Virtual Filesystem (VFS) layer.

⚠️ Work in Progress: Features and interfaces may change until the first stable release.

Features

• ✅ Functional Linux filesystem with mounting support
• ✅ Basic file operations: create, read, write
• ✅ Directory operations: mkdir, rmdir, ls
• ✅ Thread-safe concurrent access
• ✅ Compatible with Linux VFS layer

Installation

# Build the kernel module
make

# Load the module
sudo insmod demofs.ko

# Create mount point and mount
sudo mkdir /mnt/demofs
sudo mount -t demo_fs none /mnt/demofs

Usage

# Navigate to filesystem
cd /mnt/demofs

# Create files and directories (requires root)
sudo touch file1
sudo mkdir subdir
sudo echo "hello demofs" > file1

# Read files
cat file1
ls -la

Unmount when done:

sudo umount /mnt/demofs
sudo rmmod demofs

Current Status

Working:

• Module loads successfully
• Mount/unmount operations
• File and directory creation (root only)
• Basic read/write operations

Known Issues:

• Non-root users cannot create files/directories
• File metadata shows ? in ls -l output
• Directory isolation needs improvement

Contributing

Contributions welcome! This is an educational project for learning Linux kernel filesystem development.

Areas needing work:

• Fix permission system for non-root users
• Proper inode metadata handling
• Improve directory isolation
• Add comprehensive error handling