Grid software developers and Grid site administrators both require realistic testbeds where they can test applications and middleware before deployment on production infrastructure. Such testbeds should be dynamically reconfigurable to allow replication of real-world configurations. While the combination of service nodes needed for a particular application may vary greatly, there is a fixed set of node types which are used frequently: these are the building blocks needed to construct testbeds.

We present GridBuilder: a web-based virtual machine (VM) manager that supports the rapid creation and customisation of Grid nodes based on standard configurations. GridBuilder allows users to create a library of filesystem images and then generate independent filesystems based on these images. Copy-on-write is used for fast initialisation and efficient use of disk space. GridBuilder uses standard Grid configuration tools to automatically configure the middleware on new Grid service nodes. Users can save and restore snapshots of nodes and can import images to create new node types.