XenServer Software Development Kit Guide 4.1.0

Overview of the XenServer API

3.3.3.1. Host storage configuration: PBDs

Let us start by considering the PBD class. A PBD_create(...) call takes a number of parameters including:

Parameter Description

host physical machine on which the PBD is available

SR the Storage Repository that the PBD connects to

device_config a string-to-string map that is provided to the host's SR-backend-driver,

containing the low-level parameters required to configure the physical storage

device(s) on which the SR is to be realized. The specific contents of the

device_config field depend on the type of the SR to which the PBD

is connected. (Executing xe sm-list will show a list of possible SR types;

the configuration field in this enumeration specifies the device_config

parameters that each SR type expects.)

For example, imagine we have an SR object s of type "nfs" (representing a directory on an NFS filer within

which VDIs are stored as VHD files); and let's say that we want a host, h, to be able to access s. In this

case we invoke PBD.create(...) specifying host h, SR s, and a value for the device_config parameter that

is the following map:

("server", "my_nfs_server.example.com"), ("serverpath", "/scratch/mysrs/sr1")

This tells the XenServer Host that SR s is accessible on host h, and further that to access SR s, the host

needs to mount the directory "/scratch/mysrs/sr1" on the NFS server named "my_nfs_server.example.com."

Like VBD objects, PBD objects also have a field called currently_attached. Storage repositories can be

attached and detached from a given host by invoking PBD.plug and PBD.unplug methods respectively.

3.3.3.2. Host networking configuration: PIFs

Host network configuration is specified by virtue of PIF objects. If a PIF object connects a network object,

n, to a host object h, then the network corresponding to n is bridged onto a physical interface (or a physical

interface plus a VLAN tag) specified by the fields of the PIF object.

For example, imagine a PIF object exists connecting host h to a network n, and that device field of the

PIF object is set to "eth0." This means that all packets on network n are bridged to the NIC in the host

corresponding to host network device "eth0."

3.4. Exporting and Importing VMs

VMs can be exported to a file and later imported to any XenServer Host. The export protocol is a simple

HTTP(S) GET, which should be performed on the master. Authorization is either standard HTTP basic

authentication, or if a session has already been obtained, this can be used. The VM to export is specified

either by UUID or by reference. To keep track of the export, a task can be created and passed in via its

reference. The request might result in a redirect if the VM's disks are only accessible on a slave.

The followwing arguments are passed on the command line:

Argument Description

session_id the reference of the session being used to authenticate; required only

when not using HTTP basic authentication

task_id the reference of the task object with which to keep track of the operation

ref the reference of the VM; required only if not using the UUID