Belkin XM Commander Manuel d'utilisateur télécharger pdf (Page 39)

7.2.2 Xen networking scripts

Xen’s virtual networking is conﬁgured by two shell scripts (by default network and

vif-bridge). These are called automatically by xend when certain events occur,

with arguments to the scripts providing further contextual information. These scripts

are found by default in /etc/xen/scripts. The names and locations of the scripts

can be conﬁgured in /etc/xen/xend-config.sxp.

network: This script is called whenever xend is started or stopped to respectively ini-

tialise or tear down the Xen virtual network. In the default conﬁguration initial-

isation creates the bridge ‘xen-br0’ and moves eth0 onto that bridge, modifying

the routing accordingly. When xend exits, it deletes the Xen bridge and removes

eth0, restoring the normal IP and routing conﬁguration.

vif-bridge: This script is called for every domain virtual interface and can conﬁgure

ﬁrewalling rules and add the vif to the appropriate bridge. By default, this adds

and removes VIFs on the default Xen bridge.

For more complex network setups (e.g. where routing is required or integrate with

existing bridges) these scripts may be replaced with customised variants for your site’s

preferred conﬁguration.

7.3 Driver Domain Conﬁguration

I/O privileges can be assigned to allow a domain to directly access PCI devices itself.

This is used to support driver domains.

Setting backend privileges is currently only supported in SXP format conﬁg ﬁles. To

allow a domain to function as a backend for others, somewhere within the vm ele-

ment of its conﬁguration ﬁle must be a backend element of the form (backend

(type)) where type may be either netif or blkif, according to the type of

virtual device this domain will service.

Note that a block backend cannot currently import virtual block devices from other

domains, and a network backend cannot import virtual network devices from other

domains. Thus (particularly in the case of block backends, which cannot import a

virtual block device as their root ﬁlesystem), you may need to boot a backend domain

from a ramdisk or a network device.

Access to PCI devices may be conﬁgured on a per-device basis. Xen will assign the

minimal set of hardware privileges to a domain that are required to control its devices.

This can be conﬁgured in either format of conﬁguration ﬁle:

• SXP Format: Include device elements of the form:

(device (pci (bus x) (dev y) (func z)))

inside the top-level vm element. Each one speciﬁes the address of a device this

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Belkin XM Commander Manuel d'utilisateur Page 39