MentOS

What is MentOS

MentOS (Mentoring Operating system) is an open source educational operating system. The goal of MentOS is to provide a project environment that is realistic enough to show how a real Operating System work, yet simple enough that students can understand and modify it in significant ways.

There are so many operating systems, why did we write MentOS? It is true, there are a lot of education operating system, BUT how many of them follow the guideline defined by Linux?

MentOS aims to have the same Linux's data structures and algorithms. It has a well-documented source code, and you can compile it on your laptop in a few seconds! If you are a beginner in Operating-System developing, perhaps MentOS is the right operating system to start with.

Developers

Main Developers:

• Enrico Fraccaroli
• Alessandro Danese
• Luigi Capogrosso
• Mirco De Marchi

Prerequisites

For compiling the main system:

• nasm
• gcc
• g++
• make
• cmake
• git

To run and try:

• qemu-system-x86

For debugging:

• ccmake
• gdb or cgdb
• xterm

Compiling MentOS

Compile and boot MentOS with qemu:

cd <clone_directory>
mkdir build
cd build
cmake ..
make
make qemu

If you want to access to the shell, use one of the usernames listed in files/passwd.

Change the scheduling algorithm

MentOS provides three different scheduling algorithms:

• Round-Robin
• Priority
• Completely Fair Scheduling

If you want to change the scheduling algorithm:

cd build
cmake ..
ccmake ..

Now you should see something like this:

BUILD_DOCUMENTATION              ON
CMAKE_BUILD_TYPE
CMAKE_INSTALL_PREFIX             /usr/local
DEBUGGING_TYPE                   DEBUG_STDIO
ENABLE_BUDDY_SYSTEM              OFF
SCHEDULER_TYPE                   SCHEDULER_RR

Select SCHEDULER_TYPE, and type Enter to scroll the three available algorithms (SCHEDULER_RR, SCHEDULER_PRIORITY, SCHEDULER_CFS). Afterwards,

type c
type g
make
make qemu

Enable to Buddy System

MentOS provides a Buddy System to manage the allocation and deallocation of page frames in the physical memory.

If you want to enable the MentOS's Buddy System:

cd build
cmake ..
ccmake ..

Now you should see something like this:

BUILD_DOCUMENTATION              ON
CMAKE_BUILD_TYPE
CMAKE_INSTALL_PREFIX             /usr/local
DEBUGGING_TYPE                   DEBUG_STDIO
ENABLE_BUDDY_SYSTEM              OFF
SCHEDULER_TYPE                   SCHEDULER_RR

Select ENABLE_BUDDY_SYSTEM, and type Enter. You should see something like this:

BUILD_DOCUMENTATION              ON
CMAKE_BUILD_TYPE
CMAKE_INSTALL_PREFIX             /usr/local
DEBUGGING_TYPE                   DEBUG_STDIO
ENABLE_BUDDY_SYSTEM              ON
SCHEDULER_TYPE                   SCHEDULER_RR

Afterwards,

type c
type g
make
make qemu

Use Debugger

If you want to use GDB to debug MentOS:

cd build
cmake ..
make
make qemu-gdb

If you did everything correctly, you should have 3 windows with:

1) - Kernel Booting on qemu
2) - Shell with video printing of statistics previously discussed
3) - Debugger cgdb with code screening