Category: Documentation

How to Add Subdomains on Namecheap

Adding subdomains on Namecheap is quick and easy. Let’s say that I have a remote computer with IP address, I want to be able to SSH into this machine, but I hate needing to remember the IP address. Well, if you have purchased a website domain name on Namecheap like I have, just add a subdomain to your website! One of my websites that I have registered with Namecheap is, so I’ll be using that as the example.  ...


How to Bypass Intel PXE Boot

You might encounter a PXE Boot loading screen on your cluster, but you don’t have PXE Boot. And your network isn’t even configured yet! Many machines built to be part of clusters will pop up to this PXE screen and will loop forever! What do you do?   Change the Boot Order Let’s say that all I want to do is boot the machine and install a new operating system. I have my trusty CentOS 7 Bootable USB installer drive...


How to Compile HPCG

HPCG, which stands for High Performance Conjugate Gradients, is a benchmark project to create a new metric for ranking HPC systems. HPCG measures the performance of basic operations including sparse matrix-vector multiplication, sparse triangular solve, vector updates, global dot products and more. The implementation is written in C++ with MPI and OpenMP support.   HPCG Reference Code There are versions of HPCG optimized for NVIDIA GPUs or Intel XEON Phis. For this blog post, I’ll show you how to...


How to Setup the Intel Compilers on a Cluster

Intel compilers like icc or icl are very useful for any cluster with Intel processors. They’ve been known to produce very efficient numerical code. If you are still a student, you can grab the student Intel Parallel Studio XE Cluster Edition, which includes Fortran and C/C++ for free for a year. Here’s our experience. If you need more information, definitely check out the official Intel Parallel Studio XE Cluster Edition guide. Dependencies You should have the GCC C and C++...


Running MPI – Common MPI Troubleshooting Problems

In this post, I’ll list some common troubleshooting problems that I have experienced with MPI libraries after I compiled MPICH on my cluster for the first time. The following assumes that: You have at least 2 nodes as part of your cluster. You have MPI compiled inside a NFS (Network File System), a shared folder. I will divide the common problems into separate sections. For my first installation of an MPI library, I was using   MPI Paths on each...


How to Fix yum Could not resolve host: repo Unknown error

You may receive a problem with yum not being able to resolve hosts when you try to install a yum package. I’m using CentOS 7. yum install wget

If you already have Internet connection and can ping, the likely problem is that you don’t have nameservers in your /etc/resolv.conf. vi /etc/resolv.conf If /etc/resolv.conf does not have any nameservers, you can add this line somewhere in the file: nameserver Note: if you have used dhclient command, you should...


How to Change hostname on CentOS 7

The best way to change hostname on CentOS 7 is editing the actual file that controls the hostname. vi /etc/hostname Originally, it is: localhost.localdomain But, we’ll delete that line and change it to: buhpc2 buhpc is our hostname, but it also has the subdomain,, that I have configured. Now, the second file that we also have to change is /etc/hosts. vi /etc/hosts The original file looks like:

You create a new line with IP address hostname subdomain. If...


How to Create SSH Keys for Secure SSH Access

Create SSH keys for SSHing SSH keys allow you to SSH into a machine without a password prompt. Before we create our SSH key, make sure that we have a ~/.ssh folder. If not, create the ~/.ssh folder. mkdir ~/.ssh Now, we can use the following command to generate an SSH public key and private key: ssh-keygen -t rsa -b 4096 -C “[email protected]” -t represents the encryption scheme. -b represents the number of bits. -C is used for e-mail identification. You...


How to Setup Shortcuts for SSH

Instead of using SSH on an IP address that you’ll definitely forget, you can use shortcuts instead! For instance, instead of typing: ssh [email protected] Wouldn’t you rather do something like:

  Creating SSH shortcuts To create shortcuts, you have to create a file inside your home directory’s .ssh folder called config.

If the ~/.ssh directory does not exist.

Now, we can create the config file.

For every IP address that you want to add a shortcut, add...


How to Set Static IP Address on CentOS 7

This blog post will show you how to set a static IP address on CentOS 7 from scratch with no prior knowledge of any information about the network. See if NetworkManager is running. NetworkManager is a network daemon that handles our network interfaces dynamically, but we’ll change our network scripts to set static configurations. We should stop this service. systemctl status NetworkManager systemctl stop NetworkManager Check what interfaces are available. nmcli d

Connect your Ethernet cable into the computer.  ...