You will use three nodes to form the cluster and one node as the cluster management node and as a cluster node it will not take part. All the nodes and the management node should be resolvable either by host file entries or by DNS.

Cluster Nodes:

cnode1:
eth0-192.168.2.151/24 – external-lan
eth1-192.168.1.200/26 – internal-lan cluster
cnode2:
eth0-192.168.2.152/24 – external-lan
eth1-192.168.1.201/26 – internal-lan cluster
cnode3:
eth0-192.168.2.153/24 – external-lan
eth1-192.168.1.202/26 – internal-lan cluster

Cluster Management Node:

centos:
eth0-192.168.2.150/24

As the cluster, its management interface and the service deamons use tcp, for the purpose of this article you can disable the firewalls at these nodes.

OS – All Nodes:
CentOS 6 Minimal

Cluster Nodes – Software Installation:

yum groupinstall "High Availability"
yum install ricci

Cluster Management Node – Software Installation:

yum groupinstall "High Availability Management"
yum install ricci

Copy this initial sample cluster config file into /etc/cluster/cluster.conf at all the nodes cnode1, cnode2, cnode3.

<?xml version="1.0"?>
<cluster config_version="1" name="cl1">
  <clusternodes>
    <clusternode name="cnode1" nodeid="1"/>
    <clusternode name="cnode2" nodeid="2"/>
    <clusternode name="cnode3" nodeid="3"/>
  </clusternodes>
</cluster>

This initial file states that the cluster name is cl1 and defines the cluster nodes.

Now some services have to be configured and started at the nodes first and then at the management node as below.

Cluster Nodes:

chkconfig iptables off
chkconfig ip6tables off
chkconfig ricci on
chkconfig cman on
chkconfig rgmanager on
chkconfig modclusterd on

Create a password for the ricci service user with

passwd ricci

service iptables stop
service ip6tables stop
service ricci start
service cman start
service rgmanager start
service modclusterd start

Cluster Management Node:

chkconfig iptables off
chkconfig ip6tables off
chkconfig luci on
chkconfig ricci on

service iptables stop
service ip6tables stop
service luci start
service ricci start

luci service is the management service that presents the web based cluster interface via https at port 8084 and can be accessed in any browser at
https://<cluster management node FQDN or hostname:8084>/

ricci service is the underlying daemon that helps in cluster configuration sync and file copy, service start, stop etc. and uses tcp port 11111.

cman, rgmanager and modclusterd are the actual cluster services which futher start other services that actually make the clustering happen and keep it live.

Open a browser and enter the conga node url which in tis case is https://centos:8084/

After clicking ‘ok’ to the initial warning information you will be presented with the login screen. Enter the root user and root password of that system and start the interface.

Now click Add cluster and add the first node cnode1 and the ricci password, click ‘ok’ and it will detect the other two nodes also, add the ricci passwords and the cluster will be added to the Cluster Management interface. The cluster can be managed and configured from this interface. Care should be taken as the cluster.conf file sometimes does not get synced to all cluster nodes, they will get fenced due to version misconfiguration. At such times copy the cluster.conf file from node1 to all the other nodes. If all the nodes are in sync then the uptime is shown in the cluster nodes list.

Getting a cluster, configuring and managing, your cluster is up, live and configured in no time and later other clusters can be added into this management interface for easy maintenance.

- Bellamkonda Sudhakar

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Install rsync

On Centos Linux type the following command:

yum install rsync

Using rsync command with password authentication

For example, i have two servers using for load balanced and called server1(192.168.1.101) and server2(192.168.1.102). I wanted to keep data in /var/www/html sync between to servers. Type the following command on server1:

rsync -avr --progress --links --rsh='/usr/bin/ssh' 192.168.1.102:/var/www/html /var/www/html

With:
-avr : archive mode (a), verbose (v), recurse into directories (r).
–progress: Show progress.
–links: copy symlinks as symlinks.
–rsh: use to specify the remote shell ssh to use.
192.168.1.102:/var/www/html: IP address of server2 and path to synchronize to server1
/var/www/html: Server1 path

Using rsync command with SSH certificate

Replace above command with following command:

rsync -avr --progress --links --rsh='/usr/bin/ssh -i /path_to_private_key' 192.168.1.102:/var/www/html /var/www/html

A sample shell script

#!/bin/bash
SOURCEPATH='source'
DESTPATH='destination'
SOURCEHOST='ip_address'
PRIVATEKEY='private_key'
LOGFILE='log_file'
SSH='/usr/bin/ssh'
rsync -avr --progress --links --rsh="'$SSH -i $PRIVATEKEY'" $SOURCEHOST:$SOURCEPATH $DESTPATH 2>&1 >> $LOGFILE

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