LostOS

LostOS is a 32-bit bare-metal x86 operating system, written mostly in C. It boots through GRUB, brings up its own kernel, and provides an interactive shell, FAT32 storage support, and a VGA text-mode editor.

Project status

LostOS is still under active development. It is meant for learning and experimentation rather than everyday use. QEMU is currently the main target; legacy hardware interfaces are used deliberately to keep the implementation understandable.

Area	Status
GRUB / Multiboot boot flow	Working
32-bit protected-mode x86 kernel	Working
VGA, keyboard, and shell	Working
ATA PIO, MBR, and FAT32	Working
File creation, editing, and removal	Working
First-boot filesystem setup	Working
Configurable shell prompt	Working
Shell scripts (/bin/*.lts)	Working
FAT long file names (LFN)	Not supported yet
Modern hardware support	Experimental / limited

Screenshots

Features

• Multiboot boot flow through GRUB.
• 32-bit protected-mode x86 kernel with GDT, IDT, and paging.
• Kernel allocator with kmalloc and kfree.
• VGA text output, hardware cursor support, colours, and scrollback.
• PS/2 keyboard driver with pt and us layouts.
• Shell with editable input, timestamped history, cursor navigation, and autocomplete.
• Linux-style prompt showing the current directory: 404@LostOS:/path$.
• ATA PIO driver, MBR parsing, and a VFS layer on top of FAT32.
• File and directory operations with relative and absolute paths.
• Built-in lost text editor with command and insert modes.
• Automatic first-boot creation of /etc, /home, /bin, and /docs.
• Persistent shell configuration in /etc/lost.cfg, including a configurable prompt.
• Simple line-based scripts: commands in /bin/<name>.lts can be run as <name>.

Architecture

GRUB
  └── Kernel
      ├── GDT / IDT / Paging / Heap
      ├── VGA / PS2 keyboard / RTC
      ├── ATA PIO → MBR → FAT32 → VFS
      └── Shell → commands / .lts scripts → lost editor

Directory	Contents
boot/	Boot code, interrupts, and GRUB configuration
kernel/arch/	GDT, IDT, and architecture-specific code
kernel/drivers/	VGA, keyboard, RTC, and ATA drivers
kernel/fs/	MBR, FAT32, and VFS
kernel/mm/	Memory management and paging
kernel/shell/	Shell, commands, and system information
kernel/editor/	The lost text editor
kernel/lib/	String helpers and path resolution
tools/	Development tools, including the FAT32 disk-image builder

Shell and paths

The shell keeps track of a current working directory, initially /home on a mounted disk. Filesystem commands accept absolute and relative paths, including . and ...

lost@lostos:/home$ cd docs
lost@lostos:/home/docs$ read info.txt
lost@lostos:/home/docs$ cd ..
lost@lostos:/home$ ls ./docs

Tab completes commands at the beginning of a line, and file or directory names in arguments. When more than one option is available, the shell prints the matches: directories are light blue and end with /; files are white.

First boot and shell configuration

New development disk images start empty. On the first successful FAT32 mount, LostOS creates /etc, /home, /bin, and /docs. It also creates /etc/lost.cfg if it is missing:

username=$2lost
hostname=$alostos
prompt=$u@$h:$p$␠
theme=default

The prompt template supports %u (username), %h (hostname), %p (current path), and %% (a literal percent sign). ␠ above represents one trailing space after $; it is not written to the actual configuration file. Values are rendered with the shell's normal colour markup, so the default $2 and $a prefixes colour the username and hostname. Changes to the file apply after the next boot.

Scripts

Create a text file named /bin/<name>.lts; each non-empty line is executed as a shell command. Invoke it by its name, without the path or extension.

lost@lostos:/home$ lost /bin/hello.lts
echo Hello from LostOS
pwd
:wq
lost@lostos:/home$ hello
Hello from LostOS
/home

Available commands

Command	Description
help	List available commands
clear	Clear the screen
echo <text>	Print text
argc ...	Show the number of received arguments
history	Show command history with timestamps
layout [pt|us]	Show or change the keyboard layout
mem	Show kernel memory statistics
mem test [-d [fail]]	Run allocator tests
paging	Show virtual-memory status and mapping details
paging test	Run the paging test
whatami	Show system information
atatest	Diagnose ATA, MBR, and FAT32
pwd	Print the current directory
cd [path]	Change directory; with no argument, return to /
ls [path]	List files and directories
read <path>	Print a file's contents
touch <path>	Create an empty file
mkdir <path>	Create a directory
rm <path>	Remove a file
rmdir <path>	Remove an empty directory
cp <source> <destination>	Copy a file
mv <source> <destination>	Move or rename a file or directory
lost <path>	Open a file in the built-in editor
tree <path>	Display the path structure

The lost editor

The editor opens and saves files through the VFS. If the file does not exist yet, it is created the first time it is saved.

lost notes.txt

Key / command	Action
i	Enter insert mode
Esc	Return to command mode
Arrow keys	Move the cursor
:w	Save the file
:q	Close the editor
:wq	Save and close

Requirements

The development flow targets Linux. On Debian, Ubuntu, and related distributions:

sudo apt install build-essential qemu-system-x86 grub-pc-bin xorriso make

You will need a compiler that can produce 32-bit x86 code, GNU as and ld, GRUB with grub-mkrescue, xorriso, and QEMU.

Build and run

git clone https://github.com/AFaria20s/LostOS.git
cd LostOS
make run

make run builds the kernel, creates the boot ISO, creates an example FAT32 disk.img, and starts QEMU.

Command	Result
make	Create os.iso
make disk.img	Create the development FAT32 disk image
make run	Build and start LostOS in QEMU
make debug	Start QEMU paused with a GDB server on port 1234, then attach GDB to kernel.bin
make clean	Remove generated build artifacts

Storage and current limitations

Disk access uses ATA PIO through the legacy IDE ports 0x1F0-0x1F7. QEMU works without extra configuration. VirtualBox and physical hardware may need an IDE compatibility mode.

The filesystem currently supports FAT 8.3 short names. The shell displays names in lowercase and lookups are case-insensitive, but FAT long file names (LFN) and original filename casing are not preserved yet.

License

Released under the MIT License.