The syslog-ng 3.0 Administrator GuideDocument version: Thirteenth
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The syslog-ng 3.0 Administrator GuideDocument version: Thirteenth
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This section describes the format of a syslog message, according to the IETF-syslog protocol (see RFC 5424-5428 http://tools.ietf.org/html/rfc5424).A syslog message consists of the following parts:
The following is a sample syslog message:[]
<34>1 2003-10-11T22:14:15.003Z mymachine.example.com su - ID47 - BOM'su root' failed for lonvick on /dev/pts/8
The message corresponds to the following format:
<priority>VERSION ISOTIMESTAMP HOSTNAME APPLICATION PID MESSAGEID STRUCTURED-DATA MSG
In this example, the Facility has the value of 4, severity is 2, so PRI is 34. The VERSION is 1. The message was created on 11 October 2003 at 10:14:15pm UTC, 3 milliseconds into the next second. The message originated from a host that identifies itself as "mymachine.example.com". The APP-NAME is "su" and the PROCID is unknown. The MSGID is "ID47". The MSG is "'su root' failed for lonvick...", encoded in UTF-8. The encoding is defined by the BOM. There is no STRUCTURED-DATA present in the message, this is indicated by "-" in the STRUCTURED-DATA field. The MSG is "'su root' failed for lonvick...".
The HEADER part of the message must be in plain ASCII format, the parameter values of the STRUCTURED-DATA part must be in UTF-8, while the MSG part should be in UTF-8. The different parts of the message are explained in the following sections.
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]](./note.png) |
Note |
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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 2.3. 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 2.4. syslog Message Severities
The HEADER part contains the following elements:
VERSION: Version number of the syslog protocol
standard. Currently this can only be 1.
ISOTIMESTAMP: The time when the message was
generated in the ISO 8601 compatible standard timestamp format
(yyyy-mm-ddThh:mm:ss+-ZONE), e.g.:
2006-06-13T15:58:00.123+01:00.
HOSTNAME: The machine that originally sent the message.
APPLICATION: The device or application that generated the message
PID: The process name or process ID of the syslog application that sent the message. It is not necessarily the process ID of the application that generated the message.
MESSAGEID: The ID number of the message.
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Note |
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The syslog-ng application supports other timestamp formats as well, like
ISO, or the PIX extended format. The timestamp used in the IETF-syslog
protocol is derived from RFC3339, which is based on ISO8601. For details,
see the |
The STRUCTURED-DATA message part may contain meta- information about the
syslog message, or application-specific information such as traffic counters or
IP addresses. STRUCTURED-DATA consists of data blocks enclosed in brackets
([]). Every block include the ID of the block, and
one or more name=value pairs. The syslog-ng application
automatically parses the STRUCTURED-DATA part of syslog messages, which can be
referenced in macros (see Section 8.5, “Macros” for details). An
example STRUCTURED-DATA block looks like:
[exampleSDID@0 iut="3" eventSource="Application" eventID="1011"][examplePriority@0 class="high"]
The MSG part contains the text of the message itself. The encoding of the text must be UTF-8 if the BOM character is present in the message. If the message does not contain the BOM character, the encoding is treated as unknown. Usually messages arriving from legacy sources do not include the BOM character.
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