NGINX supports a wide range of severity levels to make it easy to log the information you care about. Each of these levels can be used with the error_log directive to set the minimum level at which messages are logged. Here are the supported levels in lowest to highest order, along with a guide on how they’re used:
- Debug – Debugging messages that are not useful most of the time.
- Info – Informational messages that might be good to know.
- Notice – Something normal but significant happened and it should be noted.
- Warn – Something unexpected happened, however it’s not a cause for concern.
- Error – Something failed.
- Crit – A critical condition occurred.
- Alert – Immediate action is required.
- Emerg – The system is unusable.