Term	Description
Facility	The identifier used to describe the application or process that submitted the log message. Examples are mail, kernel, and ftp.
Priority	An indicator of the importance of the message. Levels are defined within syslog as guidelines, from debugging information to critical events.
Selector	A combination of one or more facilities and levels. When an incoming event matches a selector, an action is performed.
Action	What happens to an incoming message that matches a selector. Actions can write the message to a log file, echo the message to a console or other device, write the message to a logged in user, or send the message along to another syslog server.

Facility	Description
auth	Activity related to requesting name and password (getty, su, login)
authpriv	Same as auth but logged to a file that can only be read by selected users
console	Used to capture messages that would generally be directed to the system console
cron	Messages from the cron system scheduler
daemon	System daemon catch-all
ftp	Messages relating to the ftp daemon
kern	Kernel messages
local0.local7	Local facilities defined per site
lpr	Messages from the line printing system
mail	Messages relating to the mail system
mark	Pseudo event used to generate timestamps in log files
news	Messages relating to network news protocol (nntp)
ntp	Messages relating to network time protocol
user	Regular user processes
uucp	UUCP subsystem

Priority	Description
emerg	Emergency condition, such as an imminent system crash, usually broadcast to all users
alert	Condition that should be corrected immediately, such as a corrupted system database
crit	Critical condition, such as a hardware error
err	Ordinary error
warning	Warning
notice	Condition that is not an error, but possibly should be handled in a special way
info	Informational message
debug	Messages that are used when debugging programs
none	Pseudo level used to specify not to log messages.

Option	Description
-f filename	Use the contents of file filename as the message to log.
-i	Log the process ID of the logger process with each line.
-p priority	Enter the message with the specified priority (specified selector entry); the message priority can be specified numerically, or as a facility.priority pair. The default priority is user.notice.
-t tag	Mark each line added to the log with the specified tag.
message	The string arguments whose contents are concatenated together in the specified order, separated by the space

Application	Directory
httpd	/var/log/httpd
samba	/var/log/samba
cron	/var/log/
mail	/var/log/
mysql	/var/log/

*.err;kern.debug;auth.notice /dev/console
daemon,auth.notice           /var/log/messages
lpr.info                     /var/log/lpr.log
mail.*                       /var/log/mail.log
ftp.*                        /var/log/ftp.log
auth.*                       @prep.ai.mit.edu
auth.*                       root,amrood
netinfo.err                  /var/log/netinfo.log
install.*                    /var/log/install.log
*.emerg                      *
*.alert                      |program_name
mark.*                       /dev/console

						
The logger Command:

logger [-i] [-f file] [-p priority] [-t tag] [message]...