Each system log message belongs to a facility, which groups together messages that either are generated by the same source (such as a software process) or concern a similar condition or activity (such as authentication attempts). Each message is also preassigned a severity level, which indicates how seriously the triggering event affects routing platform functions.
When you configure logging for a facility and destination, you specify a severity level for each facility. Messages from the facility that are rated at that level or higher are logged to the destination
[edit system syslog]
(console | file filename | host destination | user username) {
facility severity ;
}
(For information about the destinations, see ,Directing Messages to a User Terminal,Directing Messages to the Console and Directing Messages to a Remote Machine or the Other Routing Engine.)
To log messages belonging to more than one facility to a particular destination, specify each facility and associated severity as a separate statement within the set of statements for the destination.
Table 9 lists the facilities that you can specify in configuration statements at the [edit system syslog] hierarchy level.
Table 9: JUNOS System Logging Facilities
Table 10lists the severity levels that you can specify in configuration statements at the [edit system syslog] hierarchy level. The levels from emergency through info are in order from highest severity (greatest effect on functioning) to lowest.
Unlike the other severity levels, the none level disables logging of a facility instead of indicating how seriously a triggering event affects routing functions. For more information, see Disabling Logging of a Facility
Table 10: System Log Message Severity Levels