A host computing device can include a host domain that includes an agent for configuring the operation and/or functionality of virtual machine instances and/or operating systems associated with the instances, which may be heterogeneous (i.e., running different operating systems than each other). One or more data volumes associated with the host machine can include an image of an operating system. In an embodiment the agent can access the image of the operating system and configure operating system settings, add data, and/or remove data.