A number of the filters that come with fail2ban have a _daemon directive, but there is no mention of it in the documentation and no reference to it in any of my jail definitions.

What's it for?

  • About 60s after asking this, I realized what the answer was likely to be and it turned out to be so :)
    – Dancrumb
    Dec 29, 2014 at 14:52

1 Answer 1


The daemon directive is used to construct the __prefix_line regular expression that many of these filters use.

It allows the filter to ignore lines that come from other services, but may otherwise match your regular expression.

You can see references to _daemon in the filter.d/common.conf file.

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