Netgate is offering COVID-19 aid for pfSense software users, learn more.
Troubleshooting Thread Errors with Hostnames in Aliases¶
If a large number of hostnames are present in aliases, the following error may appear in the system log:
filterdns: Unable to create monitoring thread for host myhost.example.com! It will not be monitored
This error indicated that the
filterdns daemon hit the limit of the number
of concurrent threads it could launch in order to resolve and monitor the
The cure for this is to raise the number of allowed threads per process. This
can be done by navigating from the pfSense® webGUI to System > Advanced on the System Tunables
tab. There, create an entry for
kern.threads.max_threads_per_proc and set it
After raising that value,
filterdns must be restarted. This can be done by
any method that triggers a filter reload, such as navigating to Status >
Filter Reload and clicking Reload Filter.