2.10. The structure of a log message

This section describes the format of a syslog message, according to RFC 3164 (http://www.ietf.org/rfc/rfc3164.txt). A syslog message consists of the following parts:

PRI
HEADER
MSG

The total message must be shorter than 1024 bytes.

The following is a sample syslog message: <133>Feb 25 14:09:07 webserver syslogd: restart. The message corresponds to the following format: <priority>timestamp hostname application: message. The different parts of the message are explained in the following sections.

	Note
	The syslog-ng application supports longer messages as well. For details, see the `log_msg_size()` option in Section 9.6, “Options”. However, it is not recommended to enable messages larger than the packet size when using UDP destinations.

2.10.1. The PRI message part

The PRI part of the syslog message (known as Priority value) represents the Facility and Severity of the message. Facility represents the part of the system sending the message, while severity marks its importance. The Priority value is calculated by first multiplying the Facility number by 8 and then adding the numerical value of the Severity. The possible facility and severity values are presented below.

	Note
	Facility codes may slightly vary between different platforms. The syslog-ng application accepts facility codes as numerical values as well.

Numerical Code	Facility
0	kernel messages
1	user-level messages
2	mail system
3	system daemons
4	security/authorization messages
5	messages generated internally by syslogd
6	line printer subsystem
7	network news subsystem
8	UUCP subsystem
9	clock daemon
10	security/authorization messages
11	FTP daemon
12	NTP subsystem
13	log audit
14	log alert
15	clock daemon
16-23	locally used facilities (local0-local7)

Table 2.1. syslog Message Facilities

The following table lists the severity values.

Numerical Code	Severity
0	Emergency: system is unusable
1	Alert: action must be taken immediately
2	Critical: critical conditions
3	Error: error conditions
4	Warning: warning conditions
5	Notice: normal but significant condition
6	Informational: informational messages
7	Debug: debug-level messages

Table 2.2. syslog Message Severities

2.10.2. The HEADER message part

The HEADER part contains a timestamp and the hostname (without the domain name) or the IP address of the device. The timestamp field is the local time in the Mmm dd hh:mm:ss format, where:

Mmm is the English abbreviation of the month: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec.
dd is the day of the month on two digits. If the day of the month is less than 10, the first digit is replaced with a space. (E.g., Aug 7.)
hh:mm:ss is the local time. The hour (hh) is represented in a 24-hour format. Valid entries are between 00 and 23, inclusive. The minute (mm) and second (ss) entries are between 00 and 59 inclusive.

	Note
	The syslog-ng application supports other timestamp formats as well, like ISO, or the PIX extended format. For details, see the `ts_format()` option in Section 9.6, “Options”.

2.10.3. The MSG message part

The MSG part contains the name of the program or process that generated the message, and the text of the message itself. The MSG part is usually in the following format: program[pid]: message text.

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2.9. High availability support	Home \| Contents	Chapter 3. Configuring syslog-ng

The syslog-ng Administrator Guide

Document version: 1.0.20
Release date: April 11, 2008
Latest version available at the BalaBit Documentation Page