Installation guide

6.1. LVS Components

Section 6.1.1, “pulse” shows a detailed list of each software component in an LVS router.

6.1.1. pulse

This is the controlling process which starts all other daemons related to LVS routers. At boot

time, the daemon is started by the /etc/rc.d/init.d/pulse script. It then reads the

configuration file /etc/sysconfig/ha/lvs.cf. On the active router, pulse starts the LVS

daemon. On the backup router, pulse determines the health of the active router by executing a

simple heartbeat at a user-configurable interval. If the active router fails to respond after a

user-configurable interval, it initiates failover. During failover, pulse on the backup router

instructs the pulse daemon on the active router to shut down all LVS services, starts the

send_arp program to reassign the floating IP addresses to the backup router's MAC address,

and starts the lvs daemon.

6.1.2. lvs

The lvs daemon runs on the active LVS router once called by pulse. It reads the configuration

file /etc/sysconfig/ha/lvs.cf, calls the ipvsadm utility to build and maintain the IPVS routing

table, and assigns a nanny process for each configured LVS service. If nanny reports a real

server is down, lvs instructs the ipvsadm utility to remove the real server from the IPVS routing

table.

6.1.3. ipvsadm

This service updates the IPVS routing table in the kernel. The lvs daemon sets up and

administers LVS by calling ipvsadm to add, change, or delete entries in the IPVS routing table.

6.1.4. nanny

The nanny monitoring daemon runs on the active LVS router. Through this daemon, the active

router determines the health of each real server and, optionally, monitors its workload. A

separate process runs for each service defined on each real server.

6.1.5. /etc/sysconfig/ha/lvs.cf

This is the LVS configuration file. Directly or indirectly, all daemons get their configuration

information from this file.

6.1.6. Piranha Configuration Tool

This is the Web-based tool for monitoring, configuring, and administering LVS. This is the

default tool to maintain the /etc/sysconfig/ha/lvs.cf LVS configuration file.

6.1.7. send_arp

This program sends out ARP broadcasts when the floating IP address changes from one node

to another during failover.

Chapter 1. Linux Virtual Server Overview