Logic for on-demand instantiation in a high-performance computing, HPC, system, the logic encoded in a computer-readable medium and when executed operable to: receive a connection request from a client specifying a first port number and a first host name, the first port number and the first host name advertised externally with respect to an HPC server comprising a cluster of nodes interconnected in a grid; identify a service at the HPC server corresponding to the first port number and the first host name by: accessing a list of services at the HPC server comprising a plurality of entries that each specify: a service; and a port number and a host name internal to the HPC server that correspond to a host that, when executed at one or more nodes in the cluster, provides the service; and determine whether the identified service is available; instantiate, according to the list of services at the HPC server, the host providing the identified service at one or more nodes in the cluster by: accessing a boot image, a file system, and an operating system, OS, configuration file at the HPC server corresponding to the host providing the identified service at one or more nodes in the cluster; and if the identified service is available, using the boot image, the file system and the OS configuration file to instantiate the host providing the identified service at one or more nodes in the cluster by booting one or more nodes in the cluster using the boot image. receive a connection request from a client specifying a first port number and a first host name, the first port number and the first host name advertised externally with respect to an HPC server comprising a cluster of nodes interconnected in a grid; identify a service at the HPC server corresponding to the first port number and the first host name by: accessing a list of services at the HPC server comprising a plurality of entries that each specify: a service; and a port number and a host name internal to the HPC server that correspond to a host that, when executed at one or more nodes in the cluster, provides the service; and accessing a list of services at the HPC server comprising a plurality of entries that each specify: a service; and a port number and a host name internal to the HPC server that correspond to a host that, when executed at one or more nodes in the cluster, provides the service; and a service; and a port number and a host name internal to the HPC server that correspond to a host that, when executed at one or more nodes in the cluster, provides the service; and determine whether the identified service is available; instantiate, according to the list of services at the HPC server, the host providing the identified service at one or more nodes in the cluster by: accessing a boot image, a file system, and an operating system, OS, configuration file at the HPC server corresponding to the host providing the identified service at one or more nodes in the cluster; and accessing a boot image, a file system, and an operating system, OS, configuration file at the HPC server corresponding to the host providing the identified service at one or more nodes in the cluster; and if the identified service is available, using the boot image, the file system and the OS configuration file to instantiate the host providing the identified service at one or more nodes in the cluster by booting one or more nodes in the cluster using the boot image.