Troubleshooting Starting Issues

Problem

OpenNMS is not starting anymore.

Possible Causes

Two scenarios are typical candidates that can cause OpenNMS is not starting.

Configurations

Invalid configuration changes were made in /etc/opennms/.
These files do not change by themselves.
An administrator must have changed files that causes now the starting issue.

Figure out what has changed and revert or correct it.

Upgrades

The upgrade process can also change configuration files. It’s always a good approach to check the Breaking Changes section in the release notes.

In case of upgrade configuration changes this article can help.

General Doings

Check Versions

The install guides provides a versioned compatibility matrix you can use as reference.

Check the logs

The output.log file should be investigated for problems.

To find issues in the log use:
grep -i 'error\|exception\|caused by' /var/log/opennms/output.log

In a Dockered OpenNMS the approach differs:
docker logs horizon 2>&1 | grep -i 'error\|exception\|caused by'

Config Tester

The configuration tester offers errors in the current configuration.

Name Resolution

OpenNMS has to be able to resolve localhost. The error that appears if it’s not possible looks like:

at org.opennms-netmgt.vmmgr.Manager.testGetLocalhost(Manager.java:248)
...
Caused by: java.net.UnkownHostException:
...

Configuration Management Hint

To prevent configuration change issues in future it is a good approach to use Git to manage your configuration files to have a better overview about changes in configuration files.