Apple Mac OS X Server (Administrator’s Guide) - Manual (Page 504)

504 Chapter 12
To allow or deny client access to the NetBoot service:
1 Open Server Settings and click the Network tab.
2 Click DHCP/NetBoot and choose Configure DHCP/NetBoot.
3 Click the Filter tab.
4 Select the clients you want to allow access and which you want to deny access to the NetBoot
service.
Load Balancing
NetBoot provides a significant benefit to those system administrators tasked with
maintaining a large number of Macintosh computers by having all of those computers boot
from the same system software image. This feature, however, makes it critical that the
NetBoot server remain available to the client computer relying upon it. To provide
responsive and reliable NetBoot service, you should set up redundant NetBoot servers in
your network infrastructure.
Most sites using NetBoot achieve acceptable responsiveness by staggering the boot times of
client computers in order to reduce network load. Generally, there isn’t a need to boot all
client computers at exactly the same time; rather, client computers are booted early in the
morning and just remain booted throughout the work day. For clients computers running
Mac OS 9, you can program staggered startup times using the Energy Saver control panel.
(There is no equivalent feature in Mac OS X, however.)
If heavy usage and simultaneous client startups are overloading the NetBoot server and causing
delays, you may want to consider adding additional NetBoot servers to distribute the demands
of the client computers across multiple servers (load balancing). When incorporating multiple
NetBoot servers, it is important to use switches, as the shared nature of hubs creates a single
shared network on which additional servers would have to vie for time.
Enabling Server Selection
If you add a second NetBoot server to a network that has a single server already in use, you
will need to delete the bsdpd_clients file (located in the directory path /var/db/) from the
existing NetBoot server. This enables clients to select which server they will use as their
NetBoot server. Similarly, if you are recovering from a server or infrastructure failure, and
your clients have been booting from a reduced number of NetBoot servers, you will need to
delete the bsdpd_clients file from the running servers so that clients can once again spread
out across the entire set of servers.