== Install mpich2 ==
=== 1. Testbed Introduction ===
 * VMware Workstation 5.0
 * Create three nodes, client-01 ~ client-03, all with 5GB HD and 128MB memory.
 * The OS on these 3 nodes is Ubuntu-7.10-server
 * hostname and IP are:
  * client-01 192.168.180.131
  * client-02 192.168.180.132
  * client-03 192.168.180.133
=== 2. Getting Start to install mpich2 ===
 * '''Step 1''' : Modify /etc/hosts
  * Assume that we got 3 machines in our testbed, now we have to edit /etc/hosts on each node.[[BR]]
    Here is the example of client-01. So does the other two nodes.
{{{
root@client-01:~# cat > /etc/hosts << "EOF"
> 127.0.0.1 localhost
> 192.168.180.131 client-01
> 192.168.180.132 client-02
> 192.168.180.133 client-03
> EOF
}}}
  * Check the /etc/hosts contents, it should be like this.
{{{
root@client-01:~# cat /etc/hosts
127.0.0.1 localhost
192.168.180.131 client-01
192.168.180.132 client-02
192.168.180.133 client-03
}}}
  * Notice that if there is __127.0.0.1 client-01__ in /etc/hosts, it must be deleted.
----
 * '''Step 2''' : Download and Install mpich2
  * We use mpcich2-1.0.7rc1 for example.
{{{
root@client-01:~# wget http://www.mcs.anl.gov/research/projects/mpich2/downloads/tarballs/mpich2-1.0.7rc1.tar.gz
root@client-01:~# tar -zxvf mpich2-1.0.7rc1.tar.gz
cd mpich2-1.0.7rc1/
}}}
  * You could choose the install location as you wish, but all the nodes must have the same install location!! [[BR]]
    We use ''/opt/mpich2'' here for example.
{{{
root@client-01:~/mpich2-1.0.7rc1# ./configure prefix=/opt/mpich2
}}}
   * If there are errors when configuring mpich2, you may need some packages or libraries such as c/c++ compiler.[[BR]]
     Try this :
{{{
root@client-01:~/mpich2-1.0.7rc1# apt-get install build-essential
}}}
  * compile and install
{{{
root@client-01:~/mpich2-1.0.7rc1# make
root@client-01:~/mpich2-1.0.7rc1# make install
}}}
----
 * '''Step 3''' : Check if the Installation is Successful
  * Try these commands to see if the mpich2 have been installed correctly.
{{{
root@client-01:~/mpich2-1.0.7rc1# which mpd
/usr/local/bin/mpd
root@client-01:~/mpich2-1.0.7rc1# which mpicc
/usr/local/bin/mpicc
root@client-01:~/mpich2-1.0.7rc1# which mpiexec
/usr/local/bin/mpiexec
root@client-01:~/mpich2-1.0.7rc1# which mpirun
/usr/local/bin/mpirun
}}}
   * If there is nothing showed on the screen when enter ''which xxxx'', you probably need to set your environment variables.
{{{
root@client-01:~/mpich2-1.0.7rc1# export PATH="$PATH:/opt/mpich2/bin"
}}}
----
 * '''Step 4''' : Add New Configuration Files
  * Add ''mpd.host file'' on all the other nodes, you could put it anywhere in your system.
{{{
root@client-01:~/mpich2-1.0.7rc1# touch mpd.hosts
root@client-01:~/mpich2-1.0.7rc1# cat > mpd.hosts << "EOF"
> client-01
> client-02
> client-03
> EOF
}}}
  * Check if the content in mpd.hosts is correct.
{{{
root@client-01:~/mpich2-1.0.7rc1# cat mpd.hosts
client-01
client-02
client-03
}}}
  * Add ''/etc/mpd.conf'' on every node, there is just one line.[[BR]]
   Notice that all the nodes must have the same password.[[BR]]
   We use "this_is_password" for example here.[[BR]]
{{{
root@client-01:~/mpich2-1.0.7rc1# touch /etc/mpd.conf
root@client-01:~/mpich2-1.0.7rc1# cat > /etc/mpd.conf << "EOF"
> secretword=this_is_password
> EOF
}}}
  * Change the file properties to 600 for security consideration.
{{{
root@client-01:~/mpich2-1.0.7rc1# chmod 600 /etc/mpd.conf
}}}
----
 * '''Step 5''' : Modify SSH Connections
  * At first, you need to check if ssh have been installed on your machines.[[BR]]
    If not, you could try ''apt-get install ssh'' to install ssh.[[BR]]
    All nodes need to install ssh.[[BR]]
  * Second, now we are going to establish ssh connections between all nodes without entering password.[[BR]]
    Issue the following commands on '''ALL''' the other nodes.
{{{
root@client-01:~/mpich2-1.0.7rc1# ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa):
Created directory '/root/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.
The key fingerprint is:
d7:ad:ce:0f:e2:d8:16:3d:92:10:b8:b3:7f:7b:68:d9 root@client-01
root@client-01:~/mpich2-1.0.7rc1#
}}}
  * Just press enter when the system promoting the messages.
  * Copy id_dsa.pub and overwrite to ./authorized_keys
{{{
root@client-01:~/mpich2-1.0.7rc1# cd /root/.ssh/
root@client-01:~/.ssh# cp ./id_dsa.pub ./authorized_keys
}}}
  * Copy all files under /root/.ssh/ and overwrite the same directory on all nodes.
  * Establish ssh connections to all other nodes from node1(client-01).[[BR]]
    While connecting to the other nodes first time, you need to enter 'yes'.[[BR]]
    Since you will be automatically login as root to all the other nodes without typing any password.[[BR]]
{{{
root@client-01:~# ssh root@client-02
The authenticity of host 'client-02 (192.168.180.132)' can't be established.
RSA key fingerprint is 27:17:fa:34:63:c4:a7:c1:ec:25:84:76:6d:03:2d:96.
Are you sure you want to continue connecting (yes/no)? yes
}}}
  * '''Repeat the operations above to all the other nodes.'''(If you got 10+ machines, the will be a "big work")
  * If any error occurs, just remove /root/.ssh/known_hosts, and re-ssh.
----
 * '''Step 6''' : Start MPICH2
  * The easiest way to setup a parallelized computing environment is to issue:
{{{
root@client-01:~# mpdboot -n 3 -f /root/mpich2-1.0.7rc1/mpd.hosts
}}}
  * Check the mpich2 nodes.
{{{
root@client-01:~# mpdtrace
client-01
client-03
client-02
}}}
  * For leaving mpd program, issue this command:
{{{
root@client-01:~# mpdallexit
}}}

=== 3. Conclusion ===
 * This is the most simple parallelized computing environment, just for teaching and testing.
 * Do not expect that your job can be submitted to it and run faster! They are just virtual machines.
 * Establish MPICH2 parallelized computing environment will become very difficult when the number of nodes growing up and up.[[BR]]
   So, it is very important about how to use DRBL and Clonezilla well to help us build this parallelized environment.[[BR]]
   I will try to use DRBL to build a 10+ nodes parallelized machine later.

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