Clustering is way to connect two or more computers with each other in such a way they behave like one single computer. It’s necessary for parallel processing, load balancing, and fault tolerance which is called parallel computing. This manual shows the steps to establish clustering in Linux OS.

1. CLUSTERING
MANUAL
Parallel Computing
ABSTRACT
Clustering is way to connect two or more
computers with each other in such a way they
behave like one single computer. It’s
necessary for parallel processing, load
balancing, and fault tolerance which is called
parallel computing. This manual shows the
steps to establish clustering in Linux OS.
Khandaker Mamun Ahmed
IIT, Dhaka University

2. Contents
1 Introduction........................................................................................................ 1
2 What is clustering?.............................................................................................. 1
3 Why do we cluster? ............................................................................................ 1
4 How do we cluster multiple pcs’? ....................................................................... 1
4.1 What is MPI and MPICH? ............................................................................. 2
5 How to set npich2 cluster in Ubuntu?................................................................. 2
5.1 Defining hostnames ..................................................................................... 2
5.2 Defining a user for running MPI programs ................................................... 2
5.3 Installing ssh server...................................................................................... 5
5.4 Generate Rsa key pair for communicating the computers ........................... 5
5.5 Installing GCC and mpich2............................................................................ 6
5.6 Setting up the machinefile ........................................................................... 6
5.7 Testing ......................................................................................................... 6
6 Problem I have faced .......................................................................................... 7
6.1 solution............................................................................................................ 7

3. 1
1 INTRODUCTION
This report will discuss about the clustering and how to set MPICH in an individual’s
PC. This report is also going to answer the following questions:
 What is clustering?
 Why do we cluster multiple PCs’?
 How to cluster?
 What is MPI and MPICH?
 How to set MPICH?
 What problem I have faced during clustering?
 How did I solve that problem?
2 WHAT IS CLUSTERING?
Clustering is connecting two or more computers in such a way that they behave like
a single computer. In parallel processing, load balancing, fault tolerance clustering
is used.
3 WHY DO WE CLUSTER?
In clustering the work is divided among the computers who are interconnected
through a dedicated network to work as one centralized data processing resource.
Clusters are capable of performing multiple complex instructions by distribution
the workload. Clustering improves the systems availability to users, its aggregate
performance and overall tolerance fault and component failures. In clustering
server if a server fails it automatically shuts down and its users are switched
instantly to other servers.
4 HOW DO WE CLUSTER MULTIPLE PCS’?
This section will discuss about clustering multiple PCs’.

4. 2
4.1 WHAT IS MPI AND MPICH?
MPI stands for message passing interface which allows processes to
intercommunicate themselves to send and receive data. MPICH is a portable
implementation of MPI which is commonly used in Linux and windows structure.
5 HOW TO SET NPICH2 CLUSTER IN UBUNTU?
This section will show how to set MPICH2 cluster in Ubuntu. (This manual is created
by clustering multiple PCs’ in Ubuntu 14.04 version).
5.1 DEFINING HOSTNAMES
You can type “sudo gedit /etc/hosts” in the command line to edit the hosts file.
Here you have to put the IP addresses of yours and other computers with whom
you want to cluster your computer. Like the following
127.0.0.1 localhost
10.255.5.65 ub0
10.255.6.188 ub1
10.255.6.62 ub2
10.255.5.192 ub3
5.2 DEFINING A USER FOR RUNNING MPI PROGRAMS
Here we have to create a user for running MPI programs. We can do this by the
following:
1. Click the top most right icon. Then go to the system setting.

5. 3
Figure 1: System Settings
2. Click User Accounts. Then click unlock. Now we are able to create a new user.
Figure 2: User Accounts

6. 4
Figure 3: Create user
3. Click the + sign. Then give the account type Administrator and give the user
name mpiu and fill the other field.
Figure 4: Creating new user (mpiuser)
4. Open Terminal (Ctrl+ Alt + T) and go to the root user using “Sudo su”
command. Now you have to give password. Then type “passwd mpiuser”
command, and now you have to give the new user’s password. After this the
newly created user is activated.
5. Now logout from the current user and login the mpiu user. (Click the top
most right icon → logout. Then login the mpiu user).

7. 5
Figure 4: Login new user (mpiuser)
5.3 INSTALLING SSH SERVER
Type “sudo apt-get install openssh-server” in the terminal.
5.4 GENERATE RSA KEY PAIR FOR COMMUNICATING THE COMPUTERS
In the terminal type “ssh-keygen –t rsa”. Then type the following
cd .ssh
cat id_pub.rsa >> authorized_keys
cat authorized_keys
From the last command you can see the generated key. Do the same thing to all
the other computers you want to cluster with. Then copy all the authorized keys
to a text file. Finally paste again all the keys to the authorized_keys file. You can

8. 6
do this by typing “cat > authorized_keys” then paste all the copied keys. Finally
press “Ctrl+c”.
5.5 INSTALLING GCC AND MPICH2
In the terminal type
sudo apt-get install build-essential
sudo apt-get install mpich2
5.6 SETTING UP THE MACHINEFILE
Create a machinefile in mpiu’s home directory. Write the following in the
machinefile. First one is node name and followed by a colon the number of
processes to spawn.
ub0:2
ub1:2
ub2:2
ub3:2
5.7 TESTING
Create an mpi_hello.c file in the mpiu’s home directory and write the following in
the file.
#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);

9. 7
MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
printf("Hello from processor %d of %dn", myrank,
nprocs);
MPI_Finalize();
return 0;
}
Compile it:
mpicc mpi_hello.c -o mpi_hello
Run it:
mpiexec -n 8 -f machinefile ./mpi_hello
6 PROBLEM I HAVE FACED
port 22: No route to host
6.1 SOLUTION
 Checked the current ssh connections by the following command.
 Reinstalling the open-ssh server and client I have solved the problem. The
command is as follows:
Sudo apt-get –reinstall isntall openssh-client
openssh-server