The kubernetes plugin uses the Kubernetes client libraries, which in turn use golang/glog to log certain events. By default, glog outputs to files, and while it registers certain flags to allow customisation of this behaviour, it is not exposed in CoreDNS.

This is problematic for several reasons:

• glog does not itself perform any log file management, so without something like logrotate running alongside CoreDNS (especially problematic if running CoreDNS containerised) the log files just accumulate.
• It is desirable in some environments to run CoreDNS in a container with a read-only root filesystem for security reasons. Without a way to disable the file-based logging, this causes CoreDNS to exit whenever anything is logged via glog.