--- a/slide.md~	Sat Jun 22 12:32:52 2019 +0900
+++ b/slide.md~	Mon Jun 24 13:05:55 2019 +0900
@@ -1,89 +1,117 @@
 title: Studying Operating System Using Docker Platform  
 author: Shivani Dubey
-profile: Intern, University of the Ryukyus 
+profile: Madan Mohan Malaviya University of Technology, Gorakhpur
 
-# Why Operating System?
+## Why do we study Operating System?
 
-- Backbone of computer system
+- Every computer system has an operating system, which manages the resources of the computer.
 
-- Manages the computer's memory and processes, as well as all of its software and hardware.
+- IoT or IT Services can't work well without resource managements.
 
+- To handle it, we have to understand the API of OS.
 
-# Introduction
+- To understand the API, it is better to see the implementations.
 
-
-- Docker
+- For example, API for tuning priorities of the processes.
 
-- xv6
+## Xv6 Operating System as an educational tool
 
-What is Docker?
+- A Unix-like operating system developed in MIT, based on V6 kernel
 
+- xv6 is written in ANSI C ( not in C++ )
 
-- The modern platform for high velocity innovation.
-- Docker has products that use operating system level virtualization to develop and deliver software in packages called containers.
-- Docker can run on any computer, on any infrastructure and in any cloud.
+- xv6 is small and simple (9628 lines of codes)
+
+- It can run on Raspberry Pi ( Small PC board )
 
+- Or on ARM emulator such as QEMU
 
-What is xv6?
+## Xv6 development environment with QEMU
 
+- QEMU emulates ARM CPU with virtual memory 
 
-- A Unix-like operating system developed in MIT.
+- Xv6 operating sytem itself is running on QEMU 
 
-- xv6 is modern reimplementation of Sixth Edition Unix in ANSI C.
+- gdb debugger can be attached to the emulated program (both in user space and system space)
 
+- We can step and trace inside xv6 kernel
 
-# What helped us
-
+      ... but it requires complex development environments setup
+      ... very time consuming
 
+## Our development environments 
 
-- emacs editor (amidst the editor war between vi and emacs!)
 
 - homebrew (it simplifies installation of software in macOS)
 
 - Mercurial repository of the lab where we saved everything using ssh 
 
+- Cross Compilers 
 
-## Why Docker? 
+- ARM libraries for C language
 
-
+- QEMU (ARM Emulator)
 
-Features of Docker:
+## Introducing Docker
+
+- What is Docker? It is a container.
 
+- What is Container? An isolated envirornment such as file system.
 
-- Easy and Faster Configuration
+- It has DockerFile, which describes how to setup the envrionment in the container.
 
-- Increases productivity
+- Docker can run on any computer using an emulator such as QEMU.
 
-- Application Isolation
+- Complex development environment can be build using DockerFile and docker built command.
+
+# The DockerFile
 
-- Services
-
-- Security Management
+```
+FROM phitek/qemu-arm
+RUN apt-get update -y
+RUN apt-get remove gdb -y
+RUN apt-get install gcc-arm-none-eabi gdb-arm-none-eabi qemu-system-arm -y
+WORKDIR /code
+COPY ["src", "."]
+RUN make
+CMD /bin/bash
+```
 
+- FROM line specifies the shared image in Docker repository.
 
-## Why xv6?
-
+- apt-get installs Linux cross compiling tools.
 
+- Then it creates working directory, copies our sources to it, and executes make.
 
-- It gives a good insight into Command Line Interface of Unix OS.
+## Docker commands
+
+- Create docker image and environment, and build xv6 kernel
+
+  docker build --tag xv6-docker 
 
-- xv6 is modern reimplementation of Sixth Edition Unix in ANSI C.
+- Run xv6 kernel on QEMU in the container
+
+  docker run --rm --privileged -it xv6-docker ./run-debug.sh
 
+- Run gdb to connect the xv6 kernel running in the QEMU
 
-# Scheduling processes by their priorities
+  docker exec -it xv6-docker ./debug.sh
 
 
 
 
-- Added getpriority() and setpriority() and get_highest_priority() functions in proc.c file of xv6
+
+# Exercise : Adding priorities to the xv6 scheduler 
 
- 
+- Added getpriority() and setpriority() 
+
+- get_highest_priority() functions in proc.c file of xv6
+
+- Implemented it in schelduler()
 
 - Added a test function testpriority() in usertests.c file of xv6 to implement our algorithm
- 
 
-##  The function 
-
+##  Function used in our exercise to find highest priority process 
 ```c
 int get_highest_priority_proc(void)
 {
@@ -101,34 +129,41 @@
     rpid = pid;
     if (highest_priority > p->priority) {
        highest_priority=p->priority;
-       hpid = pid;
-    }
+       hpid = pid; }
   }
   return hpid > 0?hpid:rpid;
 }
 ```
+- It assumes at least one process to be RUNNABLE.
 
+- It may allow no highest priority process.
+
+- The correctness of the function is *important*.
 
 ## Docker Limitation
 
- 
-Mutliple images present in repository due to form command. 
+
+- If repository breaks, Docker poses a problem (a cloud problem).
 
-If repository breaks, Docker poses problem
+- Cloud may be used conveniently but we must not rely on it.
 
+- We can use a direct environment without Docker, since we have a Linux server.
+
+- Docker images can easily eat up our disk spaces.
 
-What can be done?
-
+in ~/.zsh_history
 
-We can keep track of images of Docker. 
+```c
+: 1561014922:0;docker system prune
+: 1561014973:0;docker container prune
+: 1561015350:0;docker image prune
+: 1561015362:0;docker volume prune
+```
+# Conclusion
 
 
-# Conclusion
-
 - Docker environment poses some problems, some of which are difficult to comprehend. 
 
 
-- Storage is difficult
 
-
-- Yet, it gives a good insight of the underlying important concepts of operating system beacuse it is well documented, fast and uses less resources.
\ No newline at end of file
+- Yet, it gives a good insight of the underlying important concepts of operating system because it is well documented, fast and uses less resources.