Evolution note going forward it seems reasonable to

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Evolution Note: Going forward, it seems reasonable to require that each node supports at least one of a small set of default VM types, and this set should most likely include linux-*-x86 . Perhaps this is a requirement of all nodes on the “public” PlanetLab managed by PLC, while “private” PlanetLabs are free ignore this requirement. A given physical machine might support more than one VM type, which forces us to be careful in how we describe the situation. Suppose a single machine runs Xen as its VMM, and hosts multiple VMs of type linux-xen-x86 . Suppose one of the machine’s Xen domains runs a Linux-based VMM that is capable of allocating VMs of type linux-vserver-x86 . This physical machine could be treated as a single node that hosts two VM types, but since Xen allocates a unique IP address to each domain, it is more accurately viewed as two separate nodes: one virtual and supporting VMs of type linux-vserver-x86 , and one physical and supporting VMs of type linux-xen-x86 . Each VM is initialized with two pieces of state, both provided in the RSpec given when the VM is created: a set of keys and a bootscript . Both are installed in the VM when it is created, and remain in the VM’s permanent store until it is destroyed. The keys allow the users associated with the slice to remotely access the VM using a VM-specific mechanism (e.g., ssh ). The bootscript is executed in a VM-specific way each time the VM boots. 11
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There is a distinguished VM running on each node that provides the node owner with access to the node. This VM is known as site admin for the pur- pose of remotely logging into the node, although we sometimes refer to it as the “owner-VM”. The owner-VM is granted certain privileges not afforded other VMs, including the right to inspect network traffic belonging to any local VM (e.g., run tcpdump ) and the right to execute certain privileged operations on the local node manager (see Section 4.3). Owners use this latter capability to run a script that expresses the owner’s preferences on how the node’s resources are allocated. 4.3 Node Manager A node manager (NM) is a program running on each node that creates VMs on that node, and controls the resources allocated to those VMs. All operations that manipulate VMs on a node are made through the node manager; the native VMM interface is not called directly by any other module defined in this document. There is a one-to-one mapping between nodes and node managers. The NM interface can only be called locally; VMs are remotely created indirectly through one or more infrastructure services running in regular (unprivileged) VMs. The NM typically runs in a privileged (root) VM of the underlying VMM. The NM provides an interface by which infrastructure services running on the node create VMs and bind resources to them. In addition to providing a VMM- neutral interface for creating VMs, the node manager also supports a resource pool abstraction: a collection of resources not (yet) associated with a VM. Both VMs and resource pools are described by a
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