1. A computer system, comprising: one or more processors; and one or more storage devices having stored thereon computer-executable instructions that are executable by the one or more processors and that configure the computer system to provision a virtual machine when booting an operating system from a generalized virtual machine image, including computer-executable instructions that configure the computer system to perform at least the following: create a virtual machine instance based on a generalized virtual machine image, the generalized virtual machine image comprising an operating system having boot-executable instructions that are configured to be executed during a boot time of the operating system to provision the virtual machine instance; and at the boot time of the operating system, execute the boot-executable instructions to provision the virtual machine instance, the boot-executable instructions being configured to: access a virtual storage media that is attached to the virtual machine instance, the virtual storage media including (i) provisioning data comprising one or more settings for the virtual machine instance, and (ii) a provisioning agent that is executable by the virtual machine instance for at least one or more of monitoring progress of provisioning of the virtual machine instance or reporting status of the provisioning of the virtual machine instance; acquire the provisioning data and the provisioning agent from the virtual storage media; and provision the one or more settings of the virtual machine instance according to the provisioning data, while executing the provisioning agent for at least one or more of monitoring progress of the provisioning or reporting status of the provisioning.