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Chapter 9 # Reliable Boot Service The Reliable Boot Service uses the Solaris Dynamic Host Configuration Protocol (DHCP) service and the other Foundation Services to ensure the boot of diskless nodes regardless of software or hardware failure. For information about how diskless nodes are booted and how they are allocated IP addresses, see the following sections: Introduction to the Reliable Boot Service Booting Diskless Nodes Boot Policies for Diskless Nodes ## Introduction to the Reliable Boot Service In a Foundation Services cluster, diskless nodes rely on network services to boot their operating system and run their software. The Reliable Boot Service provides a standard Solaris DHCP server on each of the master-eligible nodes. The Reliable Boot Service keeps the DHCP service operational even after failover or switchover. The Solaris DHCP servers use a public DHCP module that is configured by the DHCP administration utilities `dhcpconfig`, `pntadm`, and `dhtadm`. For information about these utilities, see their man pages. By default, the DHCP configuration files are stored on the master node. They are mounted on a mirrored file system and replicated on the vice-master node by Reliable NFS. For information about Reliable NFS, see Chapter 7, File Sharing and Data Replication. You can also put the DHCP configuration files locally on the master node and copy them to the vice-master node. For information on putting DHCP configuration files locally, see the `nhfs.conf`(4) man page. The DHCP service provides several methods of allocating IP addresses to diskless nodes at boot. The DHCP daemon is started under the control of the Daemon Monitor. If the Reliable Boot Service fails, the Daemon Monitor takes the recovery action described in the `nhpmd`(1M) man page. For further information about DHCP in the Solaris operating system, see the Solaris DHCP Service Developer's Guide. ## Booting Diskless Nodes Figure 9-1 shows the Reliable Boot Service on the master node and vice-master node, and the request for boot from a diskless node. The diskless node broadcasts a DHCP discover request to the DHCP servers on the master-eligible nodes. Only the master node responds to the DHCP discover request. After failover or switchover, the boot server on the new master node responds to the DHCP requests from diskless nodes. Figure 9-1 Request for Boot Broadcast From a Diskless Node The Reliable Boot Service is notified by the Cluster Membership Manager when a new master node is elected, or when a node joins or leaves the cluster. When a diskless node boots, the Reliable Boot Service assigns an IP address to it. If the node does not boot successfully within a specific time period, the Reliable Boot Service frees the allocated resources for the node. When a node leaves the cluster, the Reliable Boot Service retrieves the IP address that was being used by the node and clears the associated entry in the DHCP configuration files. ## Boot Policies for Diskless Nodes The method of booting diskless nodes at cluster startup is called the boot policy. There are advantages and disadvantages to each of the boot policies. Your choice depends on the hardware configuration of your cluster. For information about how to configure a boot policy the Netra High Availability Suite Foundation Services 2.1 6/03 Custom Installation Guide. This section describes the three boot policies used by the Foundation Services. ### DHCP Dynamic This boot policy creates a dynamic map between the Ethernet address of a diskless node and an IP address taken from a pool of available addresses. The map is stored in the data files for the DHCP module. The map remains valid as long as the node remains in the cluster. When the node fails or leaves the cluster, the DHCP module deletes the Ethernet address to IP address mapping. This enables the IP address to be re-enter the pool and be used by another diskless node. When a diskless node is rebooted, the DHCP module assigns a new IP address to the node. Previously allocated IP addresses are stored in a cache. The DHCP module attempts to reallocate a rebooted node with the same IP address as it had before. ### DHCP Static This boot policy maps the Ethernet address of a diskless node to a fixed IP address. This system has the advantage of statically dedicating IP addresses to specific machines, making it possible to attribute groups of software to specific machines. However, this system does not support hardware hot-swap. Furthermore, when a node fails, the Ethernet address to IP address mapping remains assigned and cannot be reused. ### DHCP Client ID This boot policy associates a `CLIENT_ID` string with a diskless node. When the diskless node is replaced, the `CLIENT_ID` string must be associated with the new node.
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