As defined by the syslog protocol, facility identifies the sub-system that generates a log. The
values local use 0-local use 7 are user-defined. The log generated by a switch can be specified
by facility. By default, local 7 is used.

Numerical Code Facility
0	kernel messages
1	user-level messages
2	mail system
3	system daemons
4	security/authorization messages (note 1)
5	messages generated internally by syslogd
6	line printer subsystem
7	network news subsystem
8	UUCP subsystem
9	clock daemon (note 2)
10	security/authorization messages (note 1)
11	FTP daemon
12	NTP subsystem
13	log audit (note 1)
14	log alert (note 1)
15	clock daemon (note 2)
16	local use 0 (local0)
17	local use 1 (local1)
18	local use 2 (local2)
19	local use 3 (local3)
20	local use 4 (local4)
21	local use 5 (local5)
22	local use 6 (local6)
23	local use 7 (local7)