Problems starting vnstat installed with brew After installing vnstat with homebrew:
brew install vnstat

and opening it, i got following error:
Error: Failed to open database &quot;/usr/local/var/db/vnstat/vnstat.db&quot; in read-only mode.
The vnStat daemon should have created the database when started.
Check that it is configured and running. See also &quot;man vnstatd&quot;

It seems, that the daemon is not running.
The solution was to start the service via brew:
sudo brew services start vnstat