Logging, monitoring, diagnostics

To read service logs use commands usual for your distribution. E.g. on distributions using systemd-journald use command journalctl -eu knot-resolver.

  groups: [manager, cache]  # enable debug logging level for some groups
  level: info  # other groups are logged based on this level
level: crit|err|warning|notice|info|debug


Logging level notice is set after start by default, so logs from Knot Resolver should contain only couple lines a day. For debugging purposes it is possible to use the very verbose debug level, but that is generally not usable unless restricted in some way (see below). On busy systems the debug-level logging can produce several MB of logs per second and will slow down operation.

In addition, your OS may provide a way to show logs only for some levels, e.g. journalctl supports passing -p warning to show lines that are warnings or more severe.

In addition to levels, logging is also divided into the groups.

groups: <list of logging groups>

Use to turn-on debug logging for the selected groups regardless of the global log level. Other groups are logged to the log based on the initial level.

Less verbose logging for DNSSEC validation errors can be enabled by using DNSSEC validation failure logging module.

target: syslog|stderr|stdout

Knot Resolver logs to standard error stream by default, but typical systemd units change that to 'syslog'. That setting logs directly through systemd’s facilities (if available) to preserve more meta-data. Do not edit if you do not know what you are doing.

Various statistics for monitoring purposes are available in Statistics collector, including export to central systems like Graphite, Metronome, InfluxDB, or Prometheus format.

Additional monitoring and debugging methods are described below. If none of these options fits your deployment or if you have special needs you can configure your own checks and exports using Asynchronous events.