[syslog-ng] What am I doing wrong?

Balazs Scheidler bazsi77 at gmail.com
Wed Dec 16 06:09:39 UTC 2020


On Wed, Dec 16, 2020, 06:04 Dan Egli <dan at newideatest.site> wrote:

> Help me understand this, please?  I have ISC dhcpd configured to log to
> syslog.local7 (since I don't see an option to force it into it's own log
> file).


Hmm syslog.local7 doesn't seem to be a facility.severity pair.

Both syslog and localX are facility codes, so either syslog or localX.

Syslog is normally reserved for the syslog subsystem, so I wouldn't use
that for dhcpd.

Also, logging and filtering based on facility codes alone is not really
flexible, as facility codes were not kept up with changes of the underlying
system. There are dedicated codes for legacy stuff like "news" which people
rarely use, but lack newer stuff like kafka or docker.

So in most cases, I see people use the PROGRAM field, or even the IP
address of devices to classify log messages.

Still, in your use case the current set of facility codes could be just
fine.

So I went into my syslog-ng file and created two filters, just
> like on the example page of syslog-ng.com:
>
> filter dhcpmsgs { facility(23) );
>

This would filter on facility code 23, each facility is mapped to a numeric
code, I can't remember what is 23, but you can check rfc3164 for the exact
assignment.

filter non_dhcp { NOT filter(dhcpmsgs) );
>

Negation should be lower case, e.g. "not"
The closing paren should be a closing brace (e.g. "}")



> I quoted almost directly from the example page on syslog-ng.com, but I
> keep getting this error when I reload syslog-ng's config:
> Error parsing filter expression, filter plugin NOT not found OR you may
> not used double quotes in your filter expression in
> /etc/syslog-ng/syslog-ng.conf:25:18-25:21:
>
> What did I do wrong? Here's the lines I modified from the syslog-ng page:
> filter demo_filter { host("example") and match("deny" value("MESSAGE")) };
> filter inverted_demo_filter { NOT filter(demo_filter) }
>
> You can see the page at:
>
> https://www.syslog-ng.com/technical-documents/doc/syslog-ng-open-source-edition/3.16/administration-guide/53
>
>
> --
> Dan Egli
>  From my Test Server
>
>
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>
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