Container Runtime OS

A lightweight multi-container runtime implemented in C on Linux, integrating user-space process management with kernel-space monitoring.

Overview

This project demonstrates core operating system concepts including process isolation, inter-process communication, logging, kernel interaction, scheduling behavior, and resource cleanup.

A supervisor process manages multiple containers concurrently, ensuring isolation using namespaces and chroot, while communicating through FIFO-based IPC. A kernel module is used to monitor container processes via IOCTL.

The runtime is also used as an experimental platform to study Linux scheduling behavior under different workloads and configurations.

---

Key Features

• Container isolation using UTS and mount namespaces with chroot
• FIFO-based IPC (cmd_pipe) for command handling
• Pipe-based logging system for container output
• Kernel module integration via character device and IOCTL
• Scheduler experiments with CPU-bound and I/O-bound workloads
• Proper resource cleanup with no zombie processes

---

System Components

User Space (engine.c)

• Long-running supervisor process
• Container lifecycle management (start, stop, ps)
• IPC using FIFO
• Logging via pipes
• IOCTL communication with kernel module

---

Kernel Space (monitor.c)

• Character device: /dev/container_monitor
• Handles IOCTL calls from user space
• Registers container PIDs
• Logs monitoring information

---

Scheduler Experiments Conducted:

• Execution of CPU-bound processes with different priorities (nice values)
• Execution of CPU-bound and I/O-bound processes simultaneously
• Observation of CPU utilization and responsiveness

Execution Steps

Build

make

Load Kernel Module

sudo insmod monitor.ko
sudo mknod /dev/container_monitor c 239 0
sudo chmod 666 /dev/container_monitor

Prepare Runtime

mkfifo cmd_pipe
gcc engine.c -o engine

Run Supervisor

sudo ./engine

Start Containers (new terminal)

echo "start alpha" > cmd_pipe
echo "start beta" > cmd_pipe
echo "ps" > cmd_pipe

View Logs

cat alpha.log

Stop Container

echo "stop alpha" > cmd_pipe

Cleanup

sudo rmmod monitor

---

Resource Cleanup (Task 6)

The system ensures proper cleanup of all resources:

• Child processes are reaped using waitpid()
• No zombie processes remain after execution
• Logging processes terminate correctly
• File descriptors are closed properly
• Kernel module releases resources on unload

---

Observations

• Containers run in isolated environments
• Logging continuously captures container output
• Kernel module successfully registers and tracks processes
• System performs clean shutdown without residual resources

---

Project Structure

• engine.c
• monitor.c
• monitor_ioctl.h
• Makefile
• cpu_test.c
• mem_test.c
• rootfs-alpha/
• rootfs-beta/
• README.md

---

Conclusion

This project demonstrates a functional container runtime combining user-space container management with kernel-space monitoring. It highlights key OS concepts while ensuring reliable execution and complete resource cleanup.