Configure System Logging

To configure the router to log system messages, include the syslog statement at the [edit system] hierarchy level:

[edit system] 

syslog {

    archive {

        files number ;

        size size ; 

        (world-readable | no-world-readable); 

    }

    file filename {

        facility level ;

        archive {

            files number ;

            size size ; 

            (world-readable | no-world-readable); 

        }

    }

    host hostname {

        facility level ;

        facility-override facility;

        log-prefix string;

    }

    user (username | *) {

        facility level ;

    }

    console {

        facility level ;

    }

}

The JUNOS system logging utility is similar to the UNIX syslogd utility, and includes the following features:

• You can direct messages to one or more destinations:

• To a named file in a local file system, by including the file statement
• To a remote machine that is running the syslogd utility, by including the host statement
• To the terminal session of one or more specific users (or all users) when they are logged into the router, by including the user statement
• To the router console, by including the console statement

• Each message is assigned to a facility, which is a group of messages that are either generated by the same software process or concern a similar condition or activity (such as authentication attempts). To log the messages belonging to one or more facilities to a particular destination, specify each facility name as a separate statement within the set of statements for the destination. Table 2 lists the JUNOS system logging facilities.
• Each message is assigned a severity level, which indicates how seriously it affects router functioning. When you configure logging for a facility and destination, you specify a severity level for each facility; messages that belong to the facility and are rated at that level or higher are logged to the destination. Table 3 lists the severity levels in order from highest to lowest.
• To prevent log files from growing too large, the JUNOS system logging utility by default writes messages to a sequence of files of a defined size. You can configure the number of files, their maximum size, and who can read them. For more information, see Configure Archiving of Log Files.
• When directing messages to a remote machine, you can configure features that make it easier to separate out JUNOS-specific messages or messages generated on particular routers. For more information, see Configure Handling of Messages Directed to a Remote Machine.

Table 2: JUNOS System Logging Facilities

Facility	Type of Event or Error
any	Any (that is, includes messages from all facilities)
authorization	Authentication and authorization attempts
change-log	Change to the JUNOS configuration
conflict-log	Configuration that is inconsistent with router hardware
cron	Actions performed or errors encountered by the cron daemon
daemon	Actions performed or errors encountered by various system daemons
firewall	Packet filtering actions performed by a firewall filter
interactive-commands	Commands issued at the JUNOS command-line interface (CLI) prompt
kernel	Actions performed or errors encountered by the JUNOS kernel
pfe	Actions performed or errors encountered by the Packet Forwarding Engine
user	Actions performed or errors encountered by various user-space processes

Table 3: System Log Message Severity Levels

Severity Level	Description
emergency	System panic or other condition that causes the router to stop functioning.
alert	Conditions that require immediate correction, such as a corrupted system database.
critical	Critical conditions, such as hard drive errors.
error	Error conditions that generally have less serious consequences than errors in the emergency, alert, and critical levels.
warning	Conditions that warrant monitoring.
notice	Conditions that are not errors but might warrant special handling.
info	Events or nonerror conditions of interest.
debug	Software debugging messages. Specify this level only when so directed by a technical support representative.

For a statement summary for the syslog statement, see the JUNOS Internet Software Configuration Guide: Getting Started.

For information about special logging features and for examples, see the following sections:

• Configure Archiving of Log Files
• Configure Handling of Messages Directed to a Remote Machine
• Examples: Configure System Logging