During configuration, you select the tool family (rsh or ssh) that will be used to synchronize the /etc/lvs.cf configuration files on the LVS routers. The selected tool must be enabled on the LVS routers, such that root 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 1 will be affected. Namely, since load information will not be available, the user-assigned weights will be applied statically rather than dynamically adjusted based on server workload.
Table 2 describes in general terms what you do to enable these tools on the source and destination hosts. For more detailed information, see the man pages. Note that, with rsh and ssh, root 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 2. Enabling Synchronization and Monitoring Tools
| Tool |
Do This |
| rsh |
Create a .rhosts file with permission 600 in the root on the destination host naming the source host and user (for example, foo.host1.com root). |
| ssh |
Obtain/install the tool, which for legal reasons is not released with international Linux distributions. On source and destination hosts, disable remote login via all other methods, set up RSA-based authentication using .ssh/authorized_keys, and start sshd. |
| uptime |
On each real server, enable either rsh or ssh as described above. |
| ruptime |
Set up each LVS router and real server to start rwhod whenever it boots. |
| rup |
Set up each real server to start rpc.rstatd whenever it boots. |
