How do configure to release and obtain VIP (virtual IP) when nginx is dead, down or system is rebooted for the kernel upgrades?

Edit /usr/local/etc/keepalived/keepalived.conf and add the following section to check whether nginx is alive or dead:
# vi /usr/local/etc/keepalived/keepalived.conf

Updated file on both lb0 and lb1:

vrrp_script chk_http_port {
script "/usr/bin/killall -0 nginx"
interval 2
weight 2
}
vrrp_instance VI_1 {
interface eth0
state MASTER
virtual_router_id 51
priority 101
authentication {
auth_type PASS
auth_pass Add-Your-Password-Here
}
track_script {
chk_http_port
}
virtual_ipaddress {
202.54.1.1/29 dev eth1
}
}

Save and close the file. Reload keealived:
# /etc/init.d/keepalived restart

If nginx died due to any issues keepalived will release master VIP and backup server will become active. When master nginx LB0 comes backs online, the backup LB1 will go down in backup state.