Synchronizing Configuration Files

Red Hat Cluster Suite: Configuring and Managing a Cluster
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# 13.7. Synchronizing Configuration Files

After configuring the primary LVS router, there are several configuration files that must be copied to the backup LVS router before you start the cluster.

These files include:

- `/etc/sysconfig/ha/lvs.cf` — the configuration file for the LVS routers.

- `/etc/sysctl` — the configuration file that, among other things, turns on packet forwarding in the kernel.

- `/etc/sysconfig/iptables` — If you are using firewall marks, you should synchronize one of these files based on which network packet filter you are using.

| Important
| The `/etc/sysctl.conf` and `/etc/sysconfig/iptables` files do not change when you configure the cluster using the Piranha Configuration Tool.

## 13.7.1. Synchronizing `lvs.cf`

Anytime the LVS configuration file, `/etc/sysconfig/ha/lvs.cf`, is created or updated, you must copy it to the backup LVS router node.

| Warning
| Both the active and backup LVS router nodes must have identical `lvs.cf` files. Mismatched LVS configuration files between the LVS router nodes can prevent failover.

The best way to do this is to use the `scp` command.

| Important
| To use `scp` the `sshd` must be running on the backup router, see Section 11.1 Configuring Services on the LVS Routers for details on how to properly configure the necessary services on the LVS routers.

Issue the following command as the root user from the primary LVS router to sync the `lvs.cf` files between the router nodes:

    scp /etc/sysconfig/ha/lvs.cf n.n.n.n:/etc/sysconfig/ha/lvs.cf

In the above command, replace `n.n.n.n` with the real IP address of the backup LVS router.

## 13.7.2. Synchronizing `sysctl`

The `sysctl` file is only modified once in most situations. This file is read at boot time and tells the kernel to turn on packet forwarding.

| Important
| If you are not sure whether or not packet forwarding is enabled in the kernel, see Section 11.5 Turning on Packet Forwarding for instructions on how to check and, if necessary, enable this key functionality.

## 13.7.3. Synchronizing Network Packet Filtering Rules

If you are using `iptables`, you will need to synchronize the appropriate configuration file on the backup LVS router.

If you alter the any network packet filter rules, enter the following command as root from the primary LVS router:

    scp /etc/sysconfig/iptables n.n.n.n:/etc/sysconfig/

In the above command, replace `n.n.n.n` with the real IP address of the backup LVS router.

Next either open an `ssh` session to the backup router or log into the machine as root and type the following command:

    /sbin/service iptables restart

Once you have copied these files over to the backup router and started the appropriate services (see Section 11.1 Configuring Services on the LVS Routers for more on this topic) you are ready to start the cluster.

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