Overview 25novdocx (en) 16 April 2010Allowing OverwritesSelect the Allow Preboot Services to Overwrite Existing Files when Uploading check box if youwant existing .zmg files to be overwritten by a newer version when the image is taken.1.3.5 Server Referral ListWhen a PXE device boots, it makes a broadcast request on the network for PXE services. TheZENworks Proxy DHCP server (novell-proxydhcp) responds to this request with information thatincludes the IP address of an Imaging Server where the device can send requests for assignedimaging work.Because PXE devices can exist in an environment with both newer and older ZENworks systemsrunning concurrently, the device can fail to determine its assigned imaging work if it cannot find theImaging Server for its own ZENworks version.In ZENworks Configuration Management, devices can exist in multiple Management Zones. It isessential that the PXE device contact PXE services assigned to its home zone so that it can correctlydetermine if there is any imaging work assigned to it. When there is only a single ManagementZone, this is easy to do because all Proxy DHCP servers provide addresses to services that belong tothe same zone. Any device can request imaging work from any Imaging Server in the same zone andget the same response.The PXE device’s initial request for PXE services is sent as a broadcast to the network, and allProxy DHCP servers respond with information pertaining to their respective zones (in ZENworksConfiguration Management and ZENworks Linux Management) or Proxy DHCP servers in theirtrees (in traditional ZENworks versions using Windows or NetWare® Imaging Servers). Because itis impossible to determine which Proxy DHCP server responds first (if multiple Proxy DHCPservers respond), or which server’s response is used by the device, it is impossible to ensure thateach PXE device will contact servers in its home zone or tree.For a ZENworks environment that has PXE services, the Server Referral List configuration sectionprovides a method for getting PXE devices to connect with their proper Imaging Servers. Serverreferral lists are only used by PXE devices, and in ZENworks Configuration Management only oneManagement Zone needs to have an active Proxy DHCP server and server referral list. Because youcan only have one referral list active in a network segment, if you have ZENworks LinuxManagement running with a referral list configured, you’ll need to disable the Proxy DHCP servicefor Linux Management. This allows the Configuration Management referral list to be used by allPXE devices.A server referral list allows you to ensure that all devices contact their home zone or tree for deviceimaging work assignments. The list should contain the IP address of an Imaging Server in eachknown Management Zone or older ZENworks system’s tree. When a device requests device imagingwork from a server, the server first determines if the device belongs to the same zone or tree as theserver. If it does not, that server refers the request to each server in its server referral list until it findsthe device’s home zone or tree. The device is then instructed to send all future requests to the correctnovell-proxydhcp.For the procedures in configuring referral lists, see Section 2.5.4, “Configuring the Server ReferralList,” on page 90.
