MiniOS - Mini Operating System Simulator

Description:

MiniOS is a mini operating system simulator. I built it to understand how operating systems actually work instead of just reading about them in theory. It has process management, file systems, user authentication, and logging.

Components

Logger: Keeps a record of everything that happens in the system. Every action gets a level (INFO, WARN, ERROR, DEBUG) and a message. Pretty straightforward.

ProcessManager: Creates and manages processes. Uses a simple Round Robin algorithm: each process gets a turn in the queue, runs, then goes back to the end. Fair scheduling, basically.

FileSystem: You can create, read, write, and delete files. Files are stored in a dictionary with content, owner, and creation time. Only the owner or root can change or delete files. Had to enforce this to avoid breaking permissions.

UserManager: Handles user login and passwords. Root user exists by default and has special permissions. Only the root can create users or view logs.

Shell: The command interface. Has 16 commands that let you actually interact with the system. Parses commands, handles quoted arguments, and sends them to the right handler.

MiniOS: Ties everything together. Boots the system, manages who's logged in, handles shutdown.

How to Use

python miniOS.py

Login:

Login username (enter for root): root
Password: root

Then use commands:

• whoami - Shows current user
• create file.txt Hello - Make a new file
• ls - List files
• read file.txt - Read file content
• write file.txt NewText - Update file
• delete file.txt - Remove file
• ps - List processes
• run bash ls - Create process
• kill 1 - Stop a process
• adduser john pass123 - Add user (root only)
• logs - View logs (root only)
• help - See all commands
• shutdown - Exit

Features

• User login with password verification
• File creation/reading/writing/deletion with ownership
• Process creation and simple Round Robin scheduling
• Root and regular user permission levels
• System logging for everything
• Terminal with command parsing
• Error handling that doesn't crash
• Everything runs in memory, so it doesn't save anything after you shut down

What I Learned

The hard parts were:

• Sharing the Logger across everything: All components needed access to the same logger so logs didn't get scattered everywhere. Had to think about how to pass it around properly.

• The scheduler: Implementing Round Robin sounds simple on paper. You take from the front, run it, and put it at the back. But handling process termination, checking if a process still exists, and keeping the queue in sync.

• File permissions: Keeping track of who owns what and stopping users from accessing files they shouldn't. Had to check ownership every single time someone tried to modify a file.

• Command parsing: Handling quoted strings like create "my file.txt" "hello world" where spaces shouldn't split the arguments. The parser had to track whether you're inside quotes or not.

• Error handling: Making sure that when something goes wrong, the system tells the user what happened and keeps running.

Files

• miniOS.py - Main code

• test_miniOS.py - Tests