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system: Collect the system-specific log messages of a platform

Starting with version 3.2, AxoSyslog can automatically collect the system-specific log messages of the host on a number of platforms using the system() driver. If the system() driver is included in the AxoSyslog configuration file, AxoSyslog automatically adds the following sources to the AxoSyslog configuration.

The system() driver is also used in the default configuration file of AxoSyslog. For details on the default configuration file, see Example: The default configuration file of [%=General.OSE%]. Starting with AxoSyslog version 3.6, you can use the system-expand command-line utility (which is a shell script, located in the modules/system-source/ directory) to display the configuration that the system() source will use.

Starting with version 3.6, AxoSyslog parses messages complying with the Splunk Common Information Model (CIM) and marked with @cim as JSON messages (for example, the ulogd from the netfilter project can emit such messages). That way, you can forward such messages without losing any information to CIM-aware applications (for example, Splunk).

Sources automatically added by AxoSyslog
PlatformMessage source
AIX unix-dgram("/dev/log");
FreeBSD unix-dgram("/var/run/log"); unix-dgram("/var/run/logpriv" perm(0600)); file("/dev/klog" follow-freq(0) program-override("kernel") flags(no-parse));

For FreeBSD versions earlier than 9.1, follow-freq(1) is used.

GNU/kFreeBSD unix-dgram("/var/run/log"); file("/dev/klog" follow-freq(0) program-override("kernel"));
HP-UX pipe("/dev/log" pad-size(2048));
Linux

Note that on Linux, the so-rcvbuf() option of the system() source is automatically set to 8192.

If the host is running under systemd, AxoSyslog reads both syslog and kernel messages directly from the systemd journal file using the systemd-journal() source. In this case, AxoSyslog doesn't read from `/dev/log` nor `/proc/kmsg`.

If the kernel of the host is version 3.5 or newer, and /dev/kmsg is seekable, AxoSyslog will use that instead of /proc/kmsg, using the multi-line-mode(indented), keep-timestamp(no), and the format(linux-kmsg) options.

If AxoSyslog is running in a jail or a Linux Container (LXC), it will not read from the /dev/kmsg or /proc/kmsg files.

  • With systemd:

    systemd-journal();

  • Without systemd, on kernel 3.5 or newer:

    unix-dgram("/dev/log"); file("/dev/kmsg" program-override("kernel") flags(kernel) format("linux-kmsg") keep-timestamp(no));

  • Without systemd, on kernels older than 3.5:

    unix-dgram("/dev/log"); file("/proc/kmsg" program-override("kernel") flags(kernel) keep-timestamp(no));
macOS file("/var/log/system.log" follow-freq(1));
NetBSD unix-dgram("/var/run/log");
Solaris 8 sun-streams("/dev/log");
Solaris 9 sun-streams("/dev/log" door("/etc/.syslog_door"));
Solaris 10 sun-streams("/dev/log" door("/var/run/syslog_door"));

1 - system() source options

The system() driver has the following options:

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

Using hook-commands() when AxoSyslog starts or stops

To execute an external program when AxoSyslog starts or stops, use the following options:

startup()

Type:string
Default:N/A

Description: Defines the external program that is executed as AxoSyslog starts.

shutdown()

Type:string
Default:N/A

Description: Defines the external program that is executed as AxoSyslog stops.

Using the hook-commands() when AxoSyslog reloads

To execute an external program when the AxoSyslog configuration is initiated or torn down, for example, on startup/shutdown or during a AxoSyslog reload, use the following options:

setup()

Type:string
Default:N/A

Description: Defines an external program that is executed when the AxoSyslog configuration is initiated, for example, on startup or during a AxoSyslog reload.

teardown()

Type:string
Default:N/A

Description: Defines an external program that is executed when the AxoSyslog configuration is stopped or torn down, for example, on shutdown or during a AxoSyslog reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as AxoSyslog is started/stopped.

The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the AxoSyslog created rule is there, packets can flow, otherwise the port is closed.

   source {
       network(transport(udp)
        hook-commands(
              startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
              shutdown("iptables -D LOGCHAIN 1")
            )
         );
    };