CEG's Linux User Group

1. Atleast Two Computers with a Linux Distribution installed in it(I'll use Ubuntu 8.04 here). To learn about installation, Click Here. Make sure that your system has GCC installed in it.
2. A network connection between them. If you have just two computers, you can connect them using an ethernet wire. Make sure that IP addresses are assigned to them. If you dont have a router to assign IP, you can statically assign them IP addresses. Click Here to know how to assign static IP addresses.
3. Eagerness to learn(I'm sure you have it!!!)

Rest of the document will assume that we are having two computers having host names node0 and node1. Let node0 be the master node.

1. The following steps are to be done for every node
2. Add the nodes to the /etc/hosts file. Open this file using your favourite text editor and add your node's IP address followed by its host name. Give one node information per line. For example,
   
   node0 10.1.1.1
   node1 10.1.1.2
3. Create a new user in both the nodes. Let us call this new user as mpiuser. You can create a new user through GUI by going to System->Administration->Users and Groups and click "Add User". Create a new user called mpiuser and give it a password. Give administrative privileges to that user. Make sure that you create the same user on all nodes. Although same password on all the nodes is not necessary, it is recommended that you do so because it'll eliminate the need to remember passwords for every node.
4. Now download and install ssh-server in every node. Execute the command sudo apt­-get install openssh­server in every machine.
5. Now logout from your session and log in as mpiuser.
6. Open terminal and type the following ssh-keygen -t dsa. This command will generate a new ssh key. On executing this command, it'll ask for a paraphrase. Leave it blank as we want to create a passwordless ssh (Assuming that you've a trusted LAN with no security issues).
7. A folder called .ssh will be created in your home directory. Its a hidden folder. This folder will contain a file id_dsa.pub that contains your public key. Now copy this key to another file called authorized_keys in the same directory. Execute the command in the terminal cd /home/mpiuser/.ssh; cat id_dsa.pub >> authorized_keys;.
8. Now download MPICH from the following website(MPICH1). Please download the MPICH 1.xx version from the website. Do not download MPICH 2 version. I was unable to get MPICH 2 to work in the cluster.
9. Untar the archive and navigate into the directory in the terminal. Execute the following commands:
   mkdir /home/mpiuser/mpich1
   ./configure --prefix=/home/mpiuser/mpich1
   make
   make install
   
10. Open the file .bashrc in your home directory. If file does not exist, create one. Copy the following code into that file
    export PATH=/home/mpiuser/mpich1/bin:$PATH
    export PATH
    LD_LIBRARY_PATH="/home/mpiuser/mpich1/lib:$LD_LIBRARY_PATH"
    export LD_LIBRARY_PATH
    
11. Now we'll define the path to MPICH for SSH. Run the following command: sudo echo /home/mpiuser/mpich1/bin >> /etc/environment
12. Now logout and login back into the user mpiuser.
13. In the folder mpich1, within the sub-directory share or util/machines/ a file called machines.LINUX will be found. Open that file and add the hostnames of all nodes except the home node ie. If you're editing the machines.LINUX file of node0, then that file will contain host names of all nodes except node0. By default MPICH executes a copy of the program in the home node. The machines.LINUX file for the machine node0 is as follows
    
    node1 : 2
    
    The number after : indicates number of cores available in each of the nodes.