As mentioned earlier, we will use two librados applications, one to calculate the MD5 hash directly on the client and another to call our RADOS class and have it calculate the MD5 hash. The two applications both need to be run from the monitor nodes in the test cluster, but can be compiled on any node and copied across if desired. For the purpose of this example, we will compile the applications directly on the monitor nodes.

Before we start, let's make sure that the build environment is present on the monitor node:

    apt-get install build-essential librados-dev