Abstract: Technologies are disclosed for generating a machine image from a software package. A machine image build service receives a request to create a machine image, such as by way of a network services application programming interface (API). The request can include the software package and a selection of an operating system. The machine image build service utilizes a workflow service to execute a workflow for generating the machine image. The workflow causes a virtual machine instance that utilizes the specified operating system to be instantiated by an on-demand computing service. The software package is installed in the virtual machine instance. A snapshot is taken of the virtual machine to create the requested machine image. The machine image can be scanned by a network service for compliance with one or more requirements for execution in a service provider network. The machine image can also be submitted to a machine image marketplace.