In the introduction of this chapter, you might have read the term configuration management. Let's understand this in more depth. Configuration management refers to how you want your VM to be configured. For example, you want an Apache webserver to host a website in a Linux VM; so, the configuration part of the VM involves:

• Installation of Apache package and dependencies
• Opening firewall ports for HTTP traffic or HTTPS traffic if you are using SSL (Secure Sockets Layer) certificates
• Enabling the service and bootstrapping it so the Apache service is started on boot

This example is for a very simple web server. Think about a complex scenario where you have a front-end web server and back-end databases, so the configuration involved is very high. So far, we've been talking about a single VM; what if you want multiple VMs with the same configuration? We are back to square one, where you have to repeat the configuration...