1. Overview

CDEHA is a custom-built High Availability system designed for two-node Linux environments. It provides automatic failover, heartbeat monitoring, IP management, and optional script hooks. This manual covers its core configuration and usage for system administrators.

2. Configuration File

Path: /etc/cdeha/config.cfg

3. Node Role

NodeRole=Primary

Set to Primary or Secondary depending on the role of the node in your HA setup.

4. Authentication

SERVICE_KEY='asecretkey';

Shared secret used to authenticate communication between both nodes. Must be the same on both.

5. Backup Node Energy Saving Mode

secondary_node_mode=active

Set to notactive only if the backup node will remain powered off for extended periods.

6. Node Network Configuration

# Primary Node
nodeP_ip=172.16.1.11
nodeP_eth=eth2
nodeP_common_eth=eth0
nodeP_common_eth_type=physical

# Secondary Node
nodeS_ip=172.16.1.21
nodeS_eth=eth2
nodeS_common_eth=eth1
nodeS_common_eth_type=physical

7. Failover Timing

SN_MAX_WAIT=60;

How long (in seconds) the secondary waits for a heartbeat before taking over.

8. Common IP Configuration

common_addr=194.154.145.133
common_netmask=255.255.255.252
FORCE_COMMON_ADDRESS_TO_PHYSICAL_ETHERNET=no

9. MAC Cloning

mac_address_clone=0
mac_address_common=00:0F:FE:0F:49:77

Enable only if required by your physical network environment.

10. External Scripts

node_check=/bin/node_check.sh
node_deactivate=/bin/node_deactivate.sh
node_activate=/bin/node_activate.sh
node_final=/bin/node_final.sh

• node_check: Monitors local health
• node_deactivate: Runs before a node is demoted
• node_activate: Runs before a node becomes active
• node_final: Final tasks after becoming active

11. System Behavior Settings

cron_check=auto
disable_pc_speaker=yes
email_account=root
debug=disable
system_performance=high

• cron_check: Auto-restart daemon if it stops
• disable_pc_speaker: Disable internal beep
• email_account: Email recipient for system alerts
• debug: Enable verbose logging (only for troubleshooting)
• system_performance: Use high, medium, or low depending on hardware

12. Deployment Checklist

13. Tips & Best Practices

• Ensure NTP time sync between nodes
• Test failover quarterly in maintenance windows
• Place override settings in /etc/cdeha/custom_config.cfg
• Use static IPs on all interfaces
• Review logs regularly for warnings and failover attempts