🚀 Sebria OS - x86 Operating System Kernel (C & Assembly)

Sebria OS is a minimal 32-bit operating system built from scratch in C and x86 Assembly, featuring a custom bootloader, VGA-based shell interface, multitasking, and a virtual file system. It is designed for educational purposes and runs inside QEMU.

Inspired by projects like AlexJMercer's Bootloader/Kernel

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🔧 Architecture Overview

🔹 Bootloader (Assembly)

• Real mode entry at 0x7C00
• BIOS-based input and output
• Loads kernel from sector 2 onward
• Switches to protected mode using a GDT

🔹 Kernel (C + Assembly)

• VGA text mode interface (80x25)
• VGA color-coded shell with UI windows
• Paging setup with flat memory model
• Cooperative multitasking via a priority-based scheduler
• User-space syscall simulation via int 0x80

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💻 Shell Features

Command	Description
print	Prints a test message
ls	Lists all files in the VFS
touch <file>	Create and write to a new file
cat <file>	Paginate through file contents
diary	Opens a text UI to save notes
ps	Shows running processes
kill <pid>	Terminates a process by PID
dump	Displays screen buffer contents
virtual	Shows virtual memory and file info
clear	Clears the shell display area
halt	Halts the OS

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📁 Virtual File System (VFS)

• Simple in-memory structure
• Max 8 inodes (MAX_INODES = 8)
• Max 2048 bytes per file (MAX_FILE_SIZE = 2048)
• Supports create, open, read, write, close, ls

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🔁 Multitasking

• Supports up to 8 processes
• Priority-based scheduling
• Kernel and simulated user-level processes

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🧪 Building & Running

🐳 Using Docker

docker run -it -v $(pwd):/work myos-build bash
make run  # or manually: qemu-system-i386 -cdrom os-image.iso -vga std

🔧 Requirements

• i686-elf-gcc
• nasm
• qemu-system-i386

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🚧 Future Work

• Disk-backed persistence (FAT/ext2)
• More robust paging and process isolation
• Basic I/O streams and redirection
• Support for external modules and drivers

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📜 License

MIT License

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👤 Author

Duc Le San Diego State University — Computer Science

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