---
title: "Kea Logging Configuration"
slug: "kea-logging-configuration"
description: "In Kea, log messages are controlled through what are known as \"loggers.\"  Basically, these are names which group together logs from specific parts of Kea. Logging provides a way to funnel messages of a specific type to a specific destination."
updated: 2023-03-11T00:08:16Z
published: 2023-03-11T00:08:16Z
canonical: "kb.isc.org/kea-logging-configuration"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://kb.isc.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Kea Logging Configuration

Kea is quite flexible in many areas, including logging. There are many ways to set up logging and loggers: in fact, too many to cover all of them in just one article. All of the details are in available in the [Kea ARM](https://kea.readthedocs.io/en/latest/arm/intro.html) in the section specifically about [Logging](https://kea.readthedocs.io/en/latest/arm/logging.html). Here are some basic guidelines which should offer enough information for most users to successfully configure logging in Kea.

## Loggers

In Kea, log messages are controlled through what are known as "loggers." Basically, these are names which group together logs from specific parts of Kea. The ARM has a [table](https://kea.readthedocs.io/en/latest/arm/logging.html#id3) of all of the available loggers. The idea here is to provide a way to funnel messages of a specific type to a specific destination (when used in conjunction with `output`, detailed below).

## Output methods

Kea offers three output methods for logs. These are `stdout` and `stderr`, `syslog`, and `/path/to/file.log`. These parameters alter the destination of the log info. Consider this example:

```
{
  "Dhcp4": {
    "loggers": [
      {
        "name": "kea-dhcp4",
        "output_options": [
          {
            "output": "stdout"
          }
        ]
      }
    ]
}
```

This will send all generated logs that are sent through the `kea-dhcp4` logger to standard out (`stdout`). If you are testing something and want to easily see logs, this is a great output method when starting Kea from the command line, as all logs will print directly to the terminal. `syslog` in the `output` setting will send the log message to the system log. You can also supply a facility example: `syslog:local7`. Finally, a file may be specified in the `output` setting, for example: `/var/log/kea/dhcp4.log`, as described below.

          Is it possible to use multiple output methods?

          

Yes! Any output method can be used with any logger regardless of what output method was used with another logger.

## Logging to a file

This method offers the easiest way of organizing log messages into separate locations by logger. In addition, it is possible to automatically rotate these files, which makes keeping detailed logs less burdensome.

## Recommended basic logging configuration

This example `loggers` configuration should meet most basic requirements:

```
{
  "Dhcp4": {
    "loggers": [
      {
        "name": "kea-dhcp4",
        "severity": "INFO",
        "output_options": [
          {
            "output": "/var/log/kea/dhcp4.log",
            "maxver": 10
          }
        ]
      },
      {
        "name": "kea-dhcp4.dhcpsrv",
        "severity": "INFO",
        "output_options": [
          {
            "output": "/var/log/kea/dhcp4-dhcpsrv.log",
            "maxver": 10
          }
        ]
      },
      {
        "name": "kea-dhcp4.leases",
        "severity": "INFO",
        "output_options": [
          {
            "output": "/var/log/kea/dhcp4-leases.log",
            "maxver": 10
          }
        ]
      }
    ]
  }
}
```

Omitted here are parameters like `maxsize` and `pattern`, which will cause the default values for these to be used. The default `pattern` should not be altered without a specific reason, as it is somewhat difficult to get right. The `maxsize` parameter specifies how large the file gets before it is rotated; the default size is 10MB. You will notice in the example above that there is a `maxver` of 10; this specifies the number of log files to be kept during rotation. In this example, there will be a maximum number of 10 log files of 10MB each of each logger setup. The maximum disk space that would be used for logs is 300MB with this configuration. This example is a good place to start for DHCPv4 logging as it should cover the most important things for troubleshooting and so on.

          What about DHCPv6?

          

These examples all used DHCPv4, but there are similar settings for DHCPv6 that allow fine control over what is logged and where.