Cluster Node Interconnection Prerequisites

During configuration, you select the tool family (either rsh or ssh) that will be used to synchronize the /etc/sysconfig/ha/lvs.cf configuration files on the LVS routers. This tool will also be used for parts of the data gathering used in determining proper load balancing. The selected tool must be enabled on the LVS routers, such that the root account on each router can log in to the other router without administrator intervention.

Also during configuration, you select the tool (uptime, ruptime, or rup) that the active router will use to monitor the workload on the real servers. Enable the selected tool on the real servers. If this cannot be done (for example, one of your real servers is a Windows/NT Web server), the cluster will still provide highly available services. However, the weighted round robin and weighted least-connections algorithms (described in Table 8-1 will be affected. Namely, since load information will not be available, the user-assigned weights will be applied statically, rather than being dynamically adjusted based on server workload.

Table 8-2 describes in general terms the steps required to enable these tools on the source and destination hosts. For more detailed information, see the appropriate man page(s). Note that, with rsh and ssh, the root account must be able to log in over the network. To enable remote root login to a Red Hat Linux system, remove the following line from the file /etc/pam.d/login:

auth required /lib/security/pam_security.so
      

This is a security hole, albeit small. Make sure you have the LVS nodes properly firewalled so that logins are allowed only from trusted sources.

Table 8-2. Enabling Synchronization and Monitoring Tools

>
ToolDo This
rsh Create a .rhosts file with permission 600 in the root account's home directory (/root) on the destination host. There should be a line in the file naming the source host and user (for example, foo.host1.com root).
ssh Create the encrption keys and necessary files in .ssh