Tuesday, 21 February 2017

Linux Kernel Debugging by Printing

http://elinux.org/Debugging_by_printing#Usage

What is Ring Buffer ?

Monday, 20 February 2017

Computer Networking tutorials for GATE people by the GATE people in a very simple language..It will be very helpful to them so,do watch it and share your reviews for the topic and the explanatory..!
If you want to learn any specific topic just mail us on:-
smit.kadvani@gmail.com OR
dhruvan.tanna1@gmail.com
Channel Name: - GATE HACK
LINK : - https://www.youtube.com/channel/UCxikHwpro-DB02ix-NovvtQ

Saturday, 18 February 2017

How to watch Temperature of CPU cores in Ubuntu ?

How to install sensors library to get temperature of CPU-Cores ?

Install lm-sensors

sudo apt-get install lm-sensors

After installation type the following in terminal

sudo sensors-detect

You may also need to run

sudo service kmod start

It will ask you few questions. Answer Yes for all of them. Finally to get your CPU temperature type sensors in your terminal.

sensors

Output:

karthick@Ubuntu-desktop:~$ sensors
coretemp-isa-0000
Adapter: ISA adapter
Core 0:      +41.0°C  (high = +78.0°C, crit = +100.0°C)  

coretemp-isa-0001
Adapter: ISA adapter
Core 1:      +41.0°C  (high = +78.0°C, crit = +100.0°C)  

w83627dhg-isa-0290
Adapter: ISA adapter
Vcore:       +1.10 V  (min =  +0.00 V, max =  +1.74 V)   
in1:         +1.60 V  (min =  +1.68 V, max =  +1.44 V)   ALARM
AVCC:        +3.30 V  (min =  +2.98 V, max =  +3.63 V)   
VCC:         +3.28 V  (min =  +2.98 V, max =  +3.63 V)   
in4:         +1.85 V  (min =  +1.66 V, max =  +1.11 V)   ALARM
in5:         +1.26 V  (min =  +1.72 V, max =  +0.43 V)   ALARM
in6:         +0.09 V  (min =  +1.75 V, max =  +0.62 V)   ALARM
3VSB:        +3.30 V  (min =  +2.98 V, max =  +3.63 V)   
Vbat:        +3.18 V  (min =  +2.70 V, max =  +3.30 V)   
fan1:          0 RPM  (min = 10546 RPM, div = 128)  ALARM
fan2:        892 RPM  (min = 2136 RPM, div = 8)  ALARM
fan3:          0 RPM  (min = 10546 RPM, div = 128)  ALARM
fan4:          0 RPM  (min = 10546 RPM, div = 128)  ALARM
fan5:          0 RPM  (min = 10546 RPM, div = 128)  ALARM
temp1:       +36.0°C  (high = +63.0°C, hyst = +55.0°C)  sensor = diode
temp2:       +39.5°C  (high = +80.0°C, hyst = +75.0°C)  sensor = diode
temp3:      +119.0°C  (high = +80.0°C, hyst = +75.0°C)  ALARM  sensor = thermistor
cpu0_vid:   +2.050 V

Monday, 13 February 2017

Sending And Receiving Using MQTT

Sending and Receiving Messages with MQTT

Intro

MQTT (Message Queue Telemetry Transport) is an ISO standard (ISO/IEC PRF 20922) publish-subscribe based “light weight” messaging protocol for use on top of the TCP/IP protocol. It is designed for connections with remote locations where a “small code footprint” is required or the network bandwidth is limited.
It’s very easy to use the MQTT protocol to exchange small messages between several devices.

Basics

A message has a topic and a payload, like the subject and the content of an e-mail.
The Publisher sends a message to the network.
The Subscriber listens for messages with a particular topic.
The Broker is responsible for coordinating the communication between publishers and subscribers. It can also store messages while subscribers are offline (a feature not used in this tutorial).

Requirements

We need a broker that is always available. Just one for the whole network. It can be a PC, a Raspberry Pi or even an EV3. If it is a Debian-based linux system we can use mosquitto

sudo apt-get install mosquitto

This installs and also starts the mosquitto daemon. You can check if it is working by using the systemctl command:

robot@ev3dev:~# systemctl status mosquitto

 ● mosquitto.service - LSB: mosquitto MQTT v3.1 message broker
   Loaded: loaded (/etc/init.d/mosquitto)
   Active: active (running) since Wed 2016-05-11 07:40:51 WEST; 7min ago
   CGroup: /system.slice/mosquitto.service
           └─685 /usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf

Now we are able to send and receive messages through the broker (by default mosquitto uses port 1883).
This tutorial uses python scripts so we need to install the python library paho-mqtt. You need ‘pip3’ to install this module, so if you have not already done so, you will need to install pip3:

sudo apt-get install python3-pip

OR

 sudo apt-get install python-pip

Now you can install paho-mqtt:

sudo pip3 install paho-mqtt

OR

 sudo pip install paho-mqtt

All scripts were tested successully on a EV3 running the latest ev3dev version (as of 21 Dec 2016) and also on a Raspberry Pi 3 with a BrickPi running the same ev3dev version and a laptop running Ubuntu 16.04.

Publisher example

A very simple script to publish a message:

#!/usr/bin/env python3

import paho.mqtt.client as mqtt

# This is the Publisher

client = mqtt.Client()
client.connect("localhost",1883,60)
client.publish("topic/test", "Hello world!");
client.disconnect();

Note: if using an external broker (i.e. the mosquitto deamon is not running in the EV3 that publishes messages) replace localhost with the IP address of the device that hosts the broker.

Subscriber example

Any MQTT client that is connected to our broker and has subscribed for “topic/test” will receive a MQTT message with “Hello world!” as the payload. We can test it with a mobile phone (there are several free MQTT client apps available) but we can also test it on our PC or on another EV3:

#!/usr/bin/env python3

import paho.mqtt.client as mqtt

# This is the Subscriber

def on_connect(client, userdata, flags, rc):
  print("Connected with result code "+str(rc))
  client.subscribe("topic/test")

def on_message(client, userdata, msg):
  if msg.payload.decode() == "Hello world!":
    print("Yes!")
    client.disconnect()
    
client = mqtt.Client()
client.connect("THE_IP_ADDRESS_OF_OUR_BROKER",1883,60)

client.on_connect = on_connect
client.on_message = on_message

client.loop_forever()

Note: the second EV3 (the “Subscriber”) just needs the “paho-mqtt” library, there is no need to install the “mosquitto” daemon.
Note: when the publisher sends a string as payload use decode() as in the example above. When the Publisher sends a number, you can use int(msg.payload) as shown in the next example.

A more practical example

We will use MQTT messages to control the speed of an EV3 motor on port A. We will do this by changing just one motor attribute: duty_cycle_sp so we define a topic for this purpose and susbcribe to it: topic/motor-A/dt

#!/usr/bin/env python3

import paho.mqtt.client as mqtt
from ev3dev.auto import *

# This is the Subscriber

m = MediumMotor(OUTPUT_A)

def on_connect(client, userdata, flags, rc):
    print("Connected with result code "+str(rc))
    client.subscribe("topic/motor-A/dt")

def on_message(client, userdata, msg):
    if (msg.payload == 'Q'):
      m.stop()
      client.disconnect()
    elif (-100 <= int(msg.payload) <= 100):
      m.duty_cycle_sp=msg.payload

client = mqtt.Client()
client.connect("THE_IP_ADDRESS_OF_OUR_BROKER",1883,60)

client.on_connect = on_connect
client.on_message = on_message

m.run_direct()
m.duty_cycle_sp=0

client.loop_forever()

So whenever a device on our network publishes a message with topic topic/motor-A/dt our Subscriber will receive it and if the payload is a proper integer value it will change the motor speed. It will also stop the motor and quit if the payload is just Q.

Reference Link :
http://www.ev3dev.org/docs/tutorials/sending-and-receiving-messages-with-mqtt/

Set of Python 3.0 in Ubuntu 16.04

How To Install Python 3 and Set Up a Local Programming Environment on Ubuntu 16.04

Introduction

This tutorial will get you up and running with a local Python 3 programming environment in Ubuntu 16.04.
Python is a versatile programming language that can be used for many different programming projects. First published in 1991 with a name inspired by the British comedy group Monty Python, the development team wanted to make Python a language that was fun to use. Easy to set up, and written in a relatively straightforward style with immediate feedback on errors, Python is a great choice for beginners and experienced developers alike. Python 3 is the most current version of the language and is considered to be the future of Python.
This tutorial will guide you through installing Python 3 on your local Linux machine and setting up a programming environment via the command line. This tutorial will explicitly cover the installation procedures for Ubuntu 16.04, but the general principles apply to any other distribution of Debian Linux.

Prerequisites

You will need a computer with Ubuntu 16.04 installed, as well as have administrative access to that machine and an internet connection.

Step 1 — Setting Up Python 3

We’ll be completing our installation and setup on the command line, which is a non-graphical way to interact with your computer. That is, instead of clicking on buttons, you’ll be typing in text and receiving feedback from your computer through text as well. The command line, also known as a shell, can help you modify and automate many of the tasks you do on a computer every day, and is an essential tool for software developers. There are many terminal commands to learn that can enable you to do more powerful things. The article “An Introduction to the Linux Terminal” can get you better oriented with the terminal.
On Ubuntu 16.04, you can find the Terminal application by clicking on the Ubuntu icon in the upper-left hand corner of your screen and typing “terminal” into the search bar. Click on the Terminal application icon to open it. Alternatively, you can hit the CTRL, ALT, and T keys on your keyboard at the same time to open the Terminal application automatically.
Ubuntu Terminal

Ubuntu 16.04 ships with both Python 3 and Python 2 pre-installed. To make sure that our versions are up-to-date, let’s update and upgrade the system with apt-get:


sudo apt-get update

sudo apt-get -y upgrade

The -y flag will confirm that we are agreeing for all items to be installed, but depending on your version of Linux, you may need to confirm additional prompts as your system updates and upgrades.
Once the process is complete, we can check the version of Python 3 that is installed in the system by typing:


python3 -V

You will receive output in the terminal window that will let you know the version number. The version number may vary, but it will look similar to this:


Output
Python 3.5.2

To manage software packages for Python, let’s install pip:


sudo apt-get install -y python3-pip  
OR 



sudo apt-get install python-pip

A tool for use with Python, pip installs and manages programming packages we may want to use in our development projects. You can install Python packages by typing:


pip3 install package_name

Here, package_name can refer to any Python package or library, such as Django for web development or NumPy for scientific computing. So if you would like to install NumPy, you can do so with the command pip3 install numpy.
There are a few more packages and development tools to install to ensure that we have a robust set-up for our programming environment:


sudo apt-get install build-essential libssl-dev libffi-dev python-dev

Once Python is set up, and pip and other tools are installed, we can set up a virtual environment for our development projects.

Step 2 — Setting Up a Virtual Environment

Virtual environments enable you to have an isolated space on your computer for Python projects, ensuring that each of your projects can have its own set of dependencies that won’t disrupt any of your other projects.
Setting up a programming environment provides us with greater control over our Python projects and over how different versions of packages are handled. This is especially important when working with third-party packages.
You can set up as many Python programming environments as you want. Each environment is basically a directory or folder in your computer that has a few scripts in it to make it act as an environment.
We need to first install the venv module, part of the standard Python 3 library, so that we can invoke the pyvenv command which will create virtual environments for us. Let’s install venv by typing:


sudo apt-get install -y python3-venv

With this installed, we are ready to create environments. Let’s choose which directory we would like to put our Python programming environments in, or we can create a new directory with mkdir, as in:


mkdir environments

cd environments

Once you are in the directory where you would like the environments to live, you can create an environment by running the following command:


pyvenv my_env

Essentially, pyvenv sets up a new directory that contains a few items which we can view with the ls command:


ls my_env


Output
bin include lib lib64 pyvenv.cfg share

Together, these files work to make sure that your projects are isolated from the broader context of your local machine, so that system files and project files don’t mix. This is good practice for version control and to ensure that each of your projects has access to the particular packages that it needs. Python Wheels, a built-package format for Python that can speed up your software production by reducing the number of times you need to compile, will be in the Ubuntu 16.04 share directory.
To use this environment, you need to activate it, which you can do by typing the following command that calls the activate script:


source my_env/bin/activate

Your prompt will now be prefixed with the name of your environment, in this case it is called my_env. Your prefix may look somewhat different, but the name of your environment in parentheses should be the first thing you see on your line:

This prefix lets us know that the environment my_env is currently active, meaning that when we create programs here they will use only this particular environment’s settings and packages.
Note: Within the virtual environment, you can use the command python instead of python3, and pip instead of pip3 if you would prefer. If you use Python 3 on your machine outside of an environment, you will need to use the python3 and pip3 commands exclusively.
After following these steps, your virtual environment is ready to use.

Step 3 — Creating a Simple Program

Now that we have our virtual environment set up, let’s create a simple “Hello, World!” program. This will make sure that our environment is working and gives us the opportunity to become more familiar with Python if we aren’t already.
To do this, we’ll open up a command-line text editor such as nano and create a new file:


nano hello.py

Once the text file opens up in the terminal window we’ll type out our program:

print("Hello, World!")

Exit nano by typing the control and x keys, and when prompted to save the file press y.
Once you exit out of nano and return to your shell, let’s run the program:


python hello.py

The hello.py program that you just created should cause your terminal to produce the following output:


Output
Hello, World!

To leave the environment, simply type the command deactivate and you will return to your original directory.

Conclusion

Congratulations! At this point you have a Python 3 programming environment set up on your local Ubuntu machine and can begin a coding project!
To set up Python 3 on another computer, follow the local programming environment guides for Debian 8, CentOS 7, Windows 10, or macOS.
With your local machine ready for software development, you can continue to learn more about coding in Python by following “Understanding Data Types in Python 3” and “How To Use Variables in Python 3”.

Reference Link:
https://www.digitalocean.com/community/tutorials/how-to-install-python-3-and-set-up-a-local-programming-environment-on-ubuntu-16-04

Sunday, 22 January 2017

How to install and run ns2 in Ubuntu in simplest Way

Installing Network Simulator 2 (NS2) on Ubuntu 14.04

1 Introduction

Network simulators are tools used to simulate discrete events in a network and which helps to predict the behaviours of a computer network. Generally the simulated networks have entities like links, switches, hubs, applications, etc. Once the simulation model is complete, it is executed to analyse the performance. Administrators can then customize the simulator to suit their needs. Network simulators typically come with support for the most popular protocols and networks in use today, such as WLAN,UDP,TCP,IP, WAN, etc.

Most simulators that are available today are based on a GUI application like the NCTUNS while some others incl. NS2 are CLI based. Simulating the network involves configuring the state elements like links, switches, hubs, terminals, etc. and also the events like packet drop rate, delivery status and so on. The most important output of the simulations are the trace files. Trace files log every packet, every event that occurred in the simulation and are used for analysis. Network simulators can also provide other tools to facilitate visual analysis of trends and potential trouble spots. Most of the simulation is performed in discrete time intervals where events that are in the queue are processed one after the other in an order.
Since simulation is a complex task, we cannot guarantee that all the simulators can provide exact or accurate results for all the different type of information. Examples of network simulators are: ns, NCTUNS, NetSim, etc.
ns2 is a name for series of discrete event network simulators like ns-1, ns-2 and ns-3. All of them are discrete-event network simulators, primarily used in research and teaching. ns2 is free software, publicly available under the GNU GPLv2 license for research, development, and use.
This post deals with the installation of "ns2" also called the "network simulator 2" in Ubuntu 14.04.

2 Download and Extract ns2

Download the all in one package for ns2 from here
The package downloaded will be named "ns-allinone-2.35.tar.gz". Copy it to the home folder. Then in a terminal use the following two commands to extract the contents of the package.:

cd ~/
tar -xvzf ns-allinone-2.35.tar.gz

All the files will be extracted into a folder called "ns-allinone-2.35".

3 Building the dependencies

Ns2 requires a few packages to be pre installed. It also requires the GCC- version 4.3 to work correctly. So install all of them by using the following command:

sudo apt-get install build-essential autoconf automake libxmu-dev

One of the dependencies mentioned is the compiler GCC-4.3, which is no longer available, and thus we have to install GCC-4.4 version. The version 4.4 is the oldest we can get. To do that, use the follwoing command:

sudo apt-get install gcc-4.4

The image below shows the output of executing both the above commands. If you have all the dependencies pre-installed, as I did, the output will look like the image below:

Note :
This very next step is not required in Ubuntu 16.04.

Once the installation is over , we have to make a change in the "ls.h" file. Use the following steps to make the changes:
Navigate to the folder "linkstate", use the following command. Here it is assumed that the ns folder extracted is in the home folder of your system.

cd ~/ns-allinone-2.35/ns-2.35/linkstate

Now open the file named "ls.h" and scroll to the 137th line. In that change the word "error" to "this->error". The image below shows the line 137 (highlighted in the image below) after making the changes to the ls.h file.To open the file use the following command:

gedit ls.h

Save that file and close it.

Now there is one more step that has to be done. We have to tell the ns which version of GCC will be used. To do so, go to your ns folder and type the following command:

Sudo gedit ns-allinone-2.34/otcl-1.13/Makefile.in

In the file, change Change CC= @CC@ to CC=gcc-4.4, as shown in the image below.

4 Installation

Now we are ready to install ns2. To do so we first require root privileges and then we can run the install script. Use the following two commands:

sudo su cd ~/ns-allinone-2.35/./install

The following is a snap of these commands:

The image below shows how it looks upon successful execution

It took almost 6 minutes to build and install ns2 on my system. But before we run it, we need to add the build path to the environment path.

5 Setting the Environment Path

The final step is to tell the system, where the files for ns2 are installed or present. To do that, we have to set the environment path using the ".bashrc" file. In that file, we need to add a few lines at the bottom. The things to be added are given below. But for the path indicated below, many of those lines have "/home/system/ns-allinone-2.35/...." , but that is where I have my extracted folder. Make sure you replace them with your path. For example, if you have installed it in a folder "/home/Download", then replace "/home/system/ns-allinone-2.35/otcl-1.14" with "/home/system/ns-allinone-2.35/otcl-1.14".
Do this for all the required lines.

sudo gedit ~/.bashrc

Lines to be added:

# LD_LIBRARY_PATH
OTCL_LIB=/home/system/ns-allinone-2.35/otcl-1.14
NS2_LIB=/home/system/ns-allinone-2.35/lib
X11_LIB=/usr/X11R6/lib
USR_LOCAL_LIB=/usr/local/lib
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$OTCL_LIB:$NS2_LIB:$X11_LIB:$USR_LOCAL_LIB
# TCL_LIBRARY
TCL_LIB=/home/system/ns-allinone-2.35/tcl8.5.10/library
USR_LIB=/usr/lib
export TCL_LIBRARY=$TCL_LIB:$USR_LIB
# PATH
XGRAPH=/home/system/ns-allinone-2.35/bin:/home/system/ns-allinone-2.35/tcl8.5.10/unix:/home/akshay/ns-allinone-2.35/tk8.5.10/unix
#the above two lines beginning from xgraph and ending with unix should come on the same line
NS=/home/system/ns-allinone-2.35/ns-2.35/ 
NAM=/home/system/ns-allinone-2.35/nam-1.15/ 
PATH=$PATH:$XGRAPH:$NS:$NAM

Once the changes have been made, save the file and restart the system.

6 Running ns2

Once the system has restarted, open a terminal and start ns2 by using the following command:

If the installation is correct then the terminal looks like the image below :

7 Links

NS2 Network Simulator

Reference Link:
https://www.howtoforge.com/tutorial/ns2-network-simulator-on-ubuntu-14.04/

Wednesday, 18 January 2017

How to create OPENMPI CLUSTER ?

Setting Up an MPICH2 Cluster in Ubuntu

This guide describes how to build a simple MPICH cluster in ubuntu.
To understand the guide, a basic knowledge of command line usage and the principle mpich
& clustering is assumed.
Here we have 4 nodes running Ubuntu server with these host names: ub0,ub1,ub2,ub3;

1. Defining hostnames in etc/hosts/
Edit /etc/hosts like these:

127.0.0.1     localhost
192.168.133.100 ub0
192.168.133.101 ub1
192.168.133.102 ub2
192.168.133.103 ub3
Note that the file shouldn't be like this:
127.0.0.1     localhost
127.0.1.1     ub0
192.168.133.100 ub0
192.168.133.101 ub1
192.168.133.102 ub2
192.168.133.103 ub3
or like this:
127.0.0.1     localhost
127.0.1.1     ub0
192.168.133.101 ub1
192.168.133.102 ub2
192.168.133.103 ub3
otherwise other hosts will try to connect to localhost when they try to reach ub0.

2. Installing NFS
NFS allows us to create a folder on the master node and have it synced on all the other nodes.
https://help.ubuntu.com/community/MpichCluster

MpichCluster Community Help Wiki
This folder can be used to store programs. To Install NFS just run this in the master node's
terminal:

omid@ub0:~$ sudo apt‐get install nfs‐server

To install the client program on other nodes run this command on each of them:
omid@ub1:~$ sudo apt‐get install nfs‐client

Note: if you want to be more efficient in controlling several nodes using same
commands, ClusterSSH is a nice tool and you can find a basic twoline tutorial here.
3. Sharing Master Folder
Make a folder in all nodes, we'll store our data and programs in this folder.
omid@ub0:~$ sudo mkdir /mirror

And then we share the contents of this folder located on the master node to all the other
nodes. In order to do this we first edit the /etc/exports file on the master node to contain the
additional line
/mirror *(rw,sync)
This can be done using a text editor such as vim or by issuing this command:

omid@ub0:~$ echo "/mirror *(rw,sync)" | sudo tee ‐a /etc/exports
Now restart the nfs service on the master node to parse this configuration once again.

omid@ub0:~$ sudo service nfs‐kernel‐server restart

Note than we store out data and programs only in master node and other nodes will access
them with NFS.

4. Mounting /master in nodes
Now all we need to do is to mount the folder on the other nodes. This can be done manually
each time like this:
omid@ub1:~$ sudo mount ub0:/mirror /mirror
omid@ub2:~$ sudo mount ub0:/mirror /mirror
omid@ub3:~$ sudo mount ub0:/mirror /mirror
But it's better to change fstab in order to mount it on every boot. We do this by editing
/etc/fstab and adding this line:
ub0:/mirror    /mirror    nfs
and remounting all partitions by issuing this on all the slave nodes:
omid@ub1:~$ sudo mount ‐a
omid@ub2:~$ sudo mount ‐a
omid@ub3:~$ sudo mount ‐a

5. Defining a user for running MPI programs
We define a user with same name and same userid in all nodes with a home directory in
/mirror.
https://help.ubuntu.com/community/MpichCluster

MpichCluster Community Help Wiki
Here we name it "mpiu"! Also we change the owner of /mirror to mpiu:
omid@ub0:~$ sudo chown mpiu /mirror

6. Installing SSH Server
Run this command in all nodes in order to install OpenSSH Server
omid@ub0:~$ sudo apt get install openssh‐server
‐

7. Setting up passwordless SSH for communication
between nodes
First we login with our new user to the master node:
omid@ub0:~$ su ‐ mpiu
Then we generate an RSA key pair for mpiu:
mpiu@ub0:~$ ssh keygen t rsa
‐
‐
You can keep the default ~/.ssh/id_rsa location. It is suggested to enter a strong passphrase for
security reasons.
Next, we add this key to authorized keys:
mpiu@ub0:~$ cd .ssh
mpiu@ub0:~/.ssh$ cat id_rsa.pub >> authorized_keys

As the home directory of mpiu in all nodes is the same (/mirror/mpiu) , there is no need to run
these commands on all nodes. If you didn't mirror the home directory, though, you can use
ssh‐copy‐id <hostname> to copy a public key to another machine's authorized_keys file
safely.

To test SSH run:
mpiu@ub0:~$ ssh ub1 hostname

If you are asked to enter a passphrase every time, you need to set up a keychain. This is done
easily by installing... Keychain.
mpiu@ub0:~$ sudo apt‐get install keychain

And to tell it where your keys are and to start an sshagent automatically edit your ~/.bashrc
file to contain the following lines (where id_rsa is the name of your private key file):
if type keychain >/dev/null 2>/dev/null; then
keychain ‐‐nogui ‐q id_rsa
[ ‐f ~/.keychain/${HOSTNAME}‐sh ] && . ~/.keychain/${HOSTNAME}‐sh
[ ‐f ~/.keychain/${HOSTNAME}‐sh‐gpg ] && . ~/.keychain/${HOSTNAME}‐sh‐gpg
fi
Exit and login once again or do a source ~/.bashrc for the changes to take effect.
Now your hostname via ssh command should return the other node's hostname without asking
for a password or a passphrase. Check that this works for all the slave nodes.

8. Installing GCC
https://help.ubuntu.com/community/MpichCluster

MpichCluster Community Help Wiki
To be able to compile all the code on our master node (it's sufficient to do it only there if we
do it inside the /mirror folder and all the libraries are in place on other machines) we need a
compiler.
You can get gcc and other necessary stuff by installing the buildessential package:
mpiu@ub0:~$ sudo apt‐get install build‐essential

9.Installing Other Compilers
Other prefered compilers should be installed before installing MPICH.
In this step you may install other compilers such as Inter Fortran, SGI compiler , ...

10. Installing MPICH2
Now the last ingredient we need installed on all the machines is the MPI implementation. You
can install MPICH2 using Synaptic by typing:
sudo apt‐get install mpich2
Alternatively, MPICH2 can be installed from source as explained in the MPICH installer
guide or you can try using some other implementation such as OpenMPI.
To test that the program did indeed install successfully enter this on all the machines:
mpiu@ub0:~$ which mpiexec
mpiu@ub0:~$ which mpirun

11. setting up a machinefile
Create a file called "machinefile" in mpiu's home directory with node names followed by a
colon and a number of processes to spawn:
ub3:4 # this will spawn 4 processes on ub3
ub2:2 # this will spawn 2 processes on ub2
ub1    # this will spawn 1 process on ub1
ub0    # this will spawn 1 process on ub0

11. Testing
Change directory to your mirror folder and write this MPI helloworld program in a file
mpi_hello.c (courtesy of this blog):

#include <stdio.h>
#include <mpi.h>
int main(int argc, char** argv) {
    int myrank, nprocs;
    MPI_Init(&argc, &argv);
    MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
    MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
    printf("Hello from processor %d of %d\n", myrank, nprocs);
    MPI_Finalize();
    return 0;
}

https://help.ubuntu.com/community/MpichCluster
MpichCluster Community Help Wiki
Compile it:
mpiu@ub0:~$ mpicc mpi_hello.c ‐o mpi_hello
and run it (the parameter next to n specifies the number of processes to spawn and distribute
among nodes):

mpiu@ub0:~$ mpiexec ‐n 8 ‐f machinefile ./mpi_hello

You should now see output similar to this:
Hello from processor 0 of 8
Hello from processor 1 of 8
Hello from processor 2 of 8
Hello from processor 3 of 8
Hello from processor 4 of 8
Hello from processor 5 of 8
Hello from processor 6 of 8
Hello from processor 7 of 8
Congratulations! You have a working MPI platform
References
For more information visit:
The official MPICH webpage
The official MPICH documentation
SSHing without a key
Using Keychain to store passphrases
A blog post explaining singlenode installation of OpenMPI
MpichCluster (last edited 20150525 20:51:36 by heemayl @
119.30.38.159[119.30.38.159]:heemayl)
https://help.ubuntu.com/community/MpichCluster
5/5

Monday, 9 January 2017

Kernel Compilation in Easiest Step

Linux kernel is the life force of all Linux family of operating systems including Ubuntu, CentOS, and Fedora.

For most part, you don’t need to compile the kernel, as it is installed by default when you install the OS. Also, when there is a critical update done to the kernel, you can use yum, or apt-get to update the kernel on your Linux system.

However you might encounter certain situation, where you may have to compile kernel from source. The following are few situation where you may have to compile Kernel on your Linux system.

Need of Kernel Compilation :

To enable experimental features that are not part of the default kernel.

To enable support for a new hardware that is not currently supported by the default kernel.

To debug the kernel

Or, just to learn how kernel works, you might want to explore the kernel source code, and compile it on your own.

In this tutorial, we’ll explain how to compile Linux kernel from source.

1. Download the Latest Stable Kernel

The first step is to download the latest stable kernel from kernel.org.

# cd /usr/src/

OR you can directly go through command line

# wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.9.3.tar.xz

2. Untar the Kernel Source

The second step is to untar the kernel source file for compilation.

# tar -xvJf linux-3.9.3.tar.xz

Or you can directly extract it by double click on tar file

3. Configure the Kernel

The kernel contains nearly 3000 configuration options. To make the kernel used by most people on most hardware, the Linux distro like Ubuntu, Fedora, Debian, RedHat, CentOS, etc, will generally include support for most common hardware. You can take any one of configuration from the distro, and on top of that you can add your own configuration, or you can configure the kernel from scratch, or you can use the default config provided by the kernel.

Do it as per your kernel version
e.g.
If you have downloaded linux 4.9.2 then

# cd linux-4.9.2

else

# cd linux-3.9.3

Then

 # make menuconfig

The make menuconfig, will launch a text-based user interface with default configuration options as shown in the figure. You should have installed “libncurses and libncurses-devel” packages for this command to work.

We will use the default config provided by the kernel. So select “Save” and save the config in the file name “.config”.
The following is a sample of the “.config” file:

CONFIG_MMU=y  CONFIG_NEED_DMA_MAP_STATE=y  CONFIG_NEED_SG_DMA_LENGTH=y  CONFIG_GENERIC_ISA_DMA=y  CONFIG_GENERIC_BUG=y  CONFIG_GENERIC_HWEIGHT=y

4. Compile the Linux Kernel

Compile the main kernel:

# make

Compile the kernel modules:

# make modules

Install the kernel modules:

# make modules_install

At this point, you should see a directory named /lib/modules/3.9.3/ in your system.

5. Install the New Kernel

Install the new kernel on the system:

# make install

The make install command will create the following files in the /boot directory.

vmlinuz-3.9.3 – The actual kernel
System.map-3.9.3 – The symbols exported by the kernel
initrd.img-3.9.3 – initrd image is temporary root file system used during boot process
config-3.9.3 – The kernel configuration file

The command “make install” will also update the grub.cfg by default. So we don’t need to manually edit the grub.cfg file.

6. Boot Linux to the new Kernel

To use the new kernel that you just compiled, reboot the system.

# reboot

Since, in grub.cfg, the new kernel is added as default boot, the system will boot from the new kernel. Just in case if you have problems with the new kernel, you can select the old kernel from the grub menu during boot and you can use your system as usual.
Once the system is up, use uname command to verify that the new version of Linux kernel is installed.

Fix this error on Debian / Ubuntu Linux

Open terminal and type the following apt-get command to install ncurses:
$ sudo apt-get install libncurses5-dev libncursesw5-dev

Now you should able to compile any program under Linux using ncurses. Here is a sample command to compile and use ncurses:

$ gcc -o output input.c -lncurses
$ ./output