SIGNALS:
Here follows a list of supported signals and their meaning; note: pmacct core
process says goodbye when its last child dies or is terminated.


Core process:
SIGCHLD:	used to handle gracefully his loved child processes;
SIGHUP:         reopens the logging infrastructure. Works with both syslog
		and logfiles;
SIGUSR1:        returns various statistics via either console or syslog; the
		syslog level used is NOTICE; the facility is selected through
		configuration (ie. key 'syslog'). The feature works for all
		daemons;
SIGUSR2:	if 'maps_refresh' config directive is enabled, it causes Core
		Process-based maps to be reloaded (ie. Pre-Tagging, BGP source
		peer ASN, NetFlow/sFlow agent to BGP peer, BGP MD5, etc.).
SIGINT:		if starting pmacct in foreground the signal is propagated to
		each running plugin, which is in turn gracefully terminated;
		if starting pmacct in background, this signal is ignored by
		the Core process but not from the plugins: it is recommended
		to send the signal to all plugins, ie. "killall -INT pmacctd"
		so to let the whole pmacct instance exit gracefully.
SIGTERM:	not handled (which means it follows the default behaviour for
		the OS) if the daemon is started in background; otherwise it 
		orks like SIGINT;
SIGPIPE:	ignored;

Plugin (SQL, noSQL, memory, print, tee, probes, etc.) processes:
SIGPIPE:	ignored;
SIGCHLD:	ignored;
SIGHUP:		inherited by Core Process; 
SIGUSR1:	ignored;
SIGUSR2:        if 'maps_refresh' configuration directive is enabled it causes
		Ports and Networks maps to be reloaded;
SIGINT:		causes the process to exit gracefully;	
