In this chapter, we will use virtual machines to build OpenJDK. During the build source code, control commands, logs, and result binaries should be sent between host and virtual machines. We will use the ubiquitous Secure Shell (SSH) protocol and its most popular implementation OpenSSH for these tasks.

SSH allows us to send data between the machines and run the commands remotely. When the client performs an SSH connection, it should be authenticated against the server. Besides the user/password authentication, OpenSSH also supports authentication using asymmetric cryptography (RSA or similar) keys. With SSH keys configured, a client can connect to server without manual intervention. This eases the scripting for copying multiple files or running remote tasks.

In this recipe, we will prepare a set of public and private keys and use these on all virtual machines and on the host machine during the build.