Facilities represent the fixed list of internal system processes that produce the log messages.
The following table lists the common facilities keywords that are available in CentOS 7 and their descriptions:
|
Facility |
Description |
|
auth or authpriv |
It represents authentication-related subsystem messages such as login |
|
cron |
It represents the crond service and any scheduled application messages |
|
daemon |
Generic name used to represent the various daemon subsystem messages |
|
kern |
It represents kernel messages |
|
lpr |
It represents legacy print service messages |
|
|
It represents all mail program messages |
|
mark |
It is for internal use and not to be used with any application |
|
news |
It represents the messages generated by NNTP |
|
security |
Same as authpriv and not used anymore |
|
syslog |
It represents the messages of the syslog daemon |
|
user |
It represents the messages generated by the user space |
|
uucp |
It represents the messages generated by the UUCP subsystem |
|
local0-local7 |
It represents the custom unused facilities provided by the system to the user for sending messages generated by user defined services |
|
* |
It matches all the facilities |
Priorities represent the severity or priority of messages that are logged for any service. There are different priority levels that can be used to determine the type of event that can be logged, such as debug, info, emerg, alert, and so on, for the specified service.
The following table lists the severity/priority levels with their description and assigned number for priority:
|
Assigned number |
Priority |
Severity description |
|
0 |
emerg |
Generates message when system is unusable |
|
1 |
alert |
Action must be taken immediately, available service is about to be discontinued |
|
2 |
crit |
Generates message when critical condition occurs |
|
3 |
err |
Non-critical error condition |
|
4 |
warning |
Warning condition |
|
5 |
notice |
Informational message for event that needs attention to prevent future issues |
|
6 |
info |
Generates informational messages for normal service operation |
|
7 |
debug |
Debugging-level messages for service operation |
If the wild card * is specified in the priority field, then it represents all types of severity (messages). If none is written in the severity field, then it means none of the messages of the corresponding facility will be added in the specified log files. The none is used to prevent logging of same message in different log files, as shown in the following diagram:
