\fI*.conf\fR files are distributed by Fail2Ban. It is recommended that *.conf files should remain unchanged to ease upgrades. If needed, customizations should be provided in \fI*.local\fR files. For example, if you would like to enable the [ssh-iptables-ipset] jail specified in jail.conf, create jail.local containing
In .local files specify only the settings you would like to change and the rest of the configuration will then come from the corresponding .conf file which is parsed first.
Configuration files have sections, those specified with [section name], and name = value pairs. For those name items that can accept multiple values, specify the values separated by spaces, or in separate lines space indented at the beginning of the line before the second value.
Configuration files can include other (defining common variables) configuration files, which is often used in Filters and Actions. Such inclusions are defined in a section called [INCLUDES]:
Fail2ban has more advanced syntax (similar python extended interpolation). This extended interpolation is using \fB%(section/parameter)s\fR to denote a value from a foreign section.
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Besides cross section interpolation the value of parameter in \fI[DEFAULT]\fR section can be retrieved with \fB%(default/parameter)s\fR.
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Fail2ban supports also another feature named \fB%(known/parameter)s\fR (means last known option with name \fBparameter\fR). This interpolation makes possible to extend a stock filter or jail regexp in .local file (opposite to simply set failregex/ignoreregex that overwrites it), e.g.
Additionally to interpolation \fB%(known/parameter)s\fR, that does not works for filter/action init parameters, an interpolation tag \fB<known/parameter>\fR can be used (means last known init definition of filters or actions with name \fBparameter\fR). This interpolation makes possible to extend a parameters of stock filter or action directly in jail inside \fIjail.conf/jail.local\fR file without creating a separately filter.d/*.local file, e.g.
Comments: use '#' for comment lines and '; ' (space is important) for inline comments. When using Python2.X, '; ' can only be used on the first line due to an Python library bug.
This is used for communication with the fail2ban server daemon. Do not remove this file when Fail2ban is running. It will not be possible to communicate with the server afterwards.
This defines where the persistent data for fail2ban is stored. This persistent data allows bans to be reinstated and continue reading log files from the last read position when fail2ban is restarted. A value of \fINone\fR disables this feature.
Max number of matches stored in database per ticket. Default: 10
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This option sets the max number of matched log-lines could be stored per ticket in the database. This also affects values resolvable via tags \fB<ipmatches>\fR and \fB<ipjailmatches>\fR in actions.
The following options are applicable to any jail. They appear in a section specifying the jail name or in the \fI[DEFAULT]\fR section which defines default values to be used if not specified in the individual section.
Optional space separated option 'tail' can be added to the end of the path to cause the log file to be read from the end, else default 'head' option reads file from the beginning
Ensure syslog or the program that generates the log file isn't configured to compress repeated log messages to "\fI*last message repeated 5 time*s\fR" otherwise it will fail to detect. This is called \fIRepeatedMsgReduction\fR in rsyslog and should be \fIOff\fR.
Force the time zone for log lines that don't have one.
If this option is not specified, log lines from which no explicit time zone has been found are interpreted by fail2ban in its own system time zone, and that may turn to be inappropriate. While the best practice is to configure the monitored applications to include explicit offsets, this option is meant to handle cases where that is not possible.
The supported time zones in this option are those with fixed offset: Z, UTC[+-]hhmm (you can also use GMT as an alias to UTC).
This option has no effect on log lines on which an explicit time zone has been found.
banning action (default iptables-multiport) typically specified in the \fI[DEFAULT]\fR section for all jails.
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This parameter will be used by the standard substitution of \fIaction\fR and can be redefined central in the \fI[DEFAULT]\fR section inside \fIjail.local\fR (to apply it to all jails at once) or separately in each jail, where this substitution will be used.
list of IPs not to ban. They can include a DNS resp. CIDR mask too. The option affects additionally to \fBignoreself\fR (if true) and don't need to contain own DNS resp. IPs of the running host.
command that is executed to determine if the current candidate IP for banning (or failure-ID for raw IDs) should not be banned. The option affects additionally to \fBignoreself\fR and \fBignoreip\fR and will be first executed if both don't hit.
Like ACTION FILES, tags like <ip> are can be included in the ignorecommand value and will be substituted before execution.
.TP
.Bignorecache
provide cache parameters (default disabled) for ignore failure check (caching of the result from `ignoreip`, `ignoreself` and `ignorecommand`), syntax:
ignorecommand = if [ "<F-USER>" = "technical" ] && [ "<ip-host>" = "my-host.example.com" ]; then exit 0; fi;
exit 1
.fi
This will cache the result of \fBignorecommand\fR (does not call it repeatedly) for 5 minutes (cache time) for maximal 100 entries (cache size), using values substituted like "user@host" as cache-keys. Set option \fBignorecache\fR to empty value disables the cache.
backend to be used to detect changes in the logpath.
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It defaults to "auto" which will try "pyinotify", "gamin", "systemd" before "polling". Any of these can be specified. "pyinotify" is only valid on Linux systems with the "pyinotify" Python libraries. "gamin" requires the "gamin" libraries.
use DNS to resolve HOST names that appear in the logs. By default it is "warn" which will resolve hostnames to IPs however it will also log a warning. If you are using DNS here you could be blocking the wrong IPs due to the asymmetric nature of reverse DNS (that the application used to write the domain name to log) compared to forward DNS that fail2ban uses to resolve this back to an IP (but not necessarily the same one). Ideally you should configure your applications to log a real IP. This can be set to "yes" to prevent warnings in the log or "no" to disable DNS resolution altogether (thus ignoring entries where hostname, not an IP is logged)..
regex (Python \fBreg\fRular \fBex\fRpression) to be added to the filter's failregexes (see \fBfailregex\fR in section FILTER FILES for details). If this is useful for others using your application please share you regular expression with the fail2ban developers by reporting an issue (see REPORTING BUGS below).
regex which, if the log line matches, would cause Fail2Ban not consider that line. This line will be ignored even if it matches a failregex of the jail or any of its filters.
max number of matched log-lines the jail would hold in memory per ticket. By default it is the same value as \fBmaxretry\fR of jail (or default). This option also affects values resolvable via tag \fB<matches>\fR in actions.
requires pyinotify (a file alteration monitor) to be installed. If pyinotify is not installed, Fail2ban will use auto.
.TP
.Bgamin
requires Gamin (a file alteration monitor) to be installed. If Gamin is not installed, Fail2ban will use auto.
.TP
.Bpolling
uses a polling algorithm which does not require external libraries.
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.Bsystemd
uses systemd python library to access the systemd journal. Specifying \fBlogpath\fR is not valid for this backend and instead utilises \fBjournalmatch\fR from the jails associated filter config.
.SSActions
Each jail can be configured with only a single filter, but may have multiple actions. By default, the name of a action is the action filename, and in the case of Python actions, the ".py" file extension is stripped. Where multiple of the same action are to be used, the \fBactname\fR option can be assigned to the action to avoid duplication e.g.:
The time entries in fail2ban configuration (like \fBfindtime\fR or \fBbantime\fR) can be provided as integer in seconds or as string using special abbreviation format (e. g. \fB600\fR is the same as \fB10m\fR).
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.BAbbreviationtokens:
.RS
.nf
years?, yea?, yy?
months?, mon?
weeks?, wee?, ww?
days?, da, dd?
hours?, hou?, hh?
minutes?, min?, mm?
seconds?, sec?, ss?
The question mark (?) means the optional character, so \fBday\fR as well as \fBdays\fR can be used.
.fi
.RE
You can combine multiple tokens in format (separated with space resp. without separator), e. g.: \fB1y 6mo\fR or \fB1d12h30m\fR.
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Note that tokens \fBm\fR as well as \fBmm\fR means minutes, for month use abbreviation \fBmo\fR or \fBmon\fR.
The time format can be tested using \fBfail2ban-client\fR:
The [Init] section enables action-specific settings. In \fIjail.conf/jail.local\fR these can be overridden for a particular jail as options of the action's specification in that jail.
The [Init] section allows for action-specific settings. In \fIjail.conf/jail.local\fR these can be overwritten for a particular jail as options to the jail. The following are special tags which can be set in the [Init] section:
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\fBtimeout\fR
The maximum period of time in seconds that a command can executed, before being killed.
Commands specified in the [Definition] section are executed through a system shell so shell redirection and process control is allowed. The commands should
return 0, otherwise error would be logged. Moreover if \fBactioncheck\fR exits with non-0 status, it is taken as indication that firewall status has changed and fail2ban needs to reinitialize itself (i.e. issue \fBactionstop\fR and \fBactionstart\fR commands).
More than a single command is allowed to be specified. Each command needs to be on a separate line and indented with whitespace(s) without blank lines. The following example defines
As per \fBfailures\fR, but total of all failures for that ip address across all jails from the fail2ban persistent database. Therefore the database must be set for this tag to function.
concatenated string of the log file lines of the matches that generated the ban. Many characters interpreted by shell get escaped to prevent injection, nevertheless use with caution.
As per \fBmatches\fR, but includes all lines for the IP which are contained with the fail2ban persistent database. Therefore the database must be set for this tag to function.
Python based actions can also be used, where the file name must be \fI[actionname].py\fR. The Python file must contain a variable \fIAction\fR which points to Python class. This class must implement a minimum interface as described by \fIfail2ban.server.action.ActionBase\fR, which can be inherited from to ease implementation.
For multiline regexs the tag \fI<SKIPLINES>\fR should be used to separate lines. This allows lines between the matched lines to continue to be searched for other failures. The tag can be used multiple times.
Similar to actions, filters have an [Init] section which can be overridden in \fIjail.conf/jail.local\fR. Besides the filter-specific settings, the filter [Init] section can be used to set following standard options:
specifies the maximum number of lines to buffer to match multi-line regexs. For some log formats this will not required to be changed. Other logs may require to increase this value if a particular log file is frequently written to.
specifies a custom date pattern/regex as an alternative to the default date detectors e.g. %Y-%m-%d %H:%M(?::%S)?. For a list of valid format directives, see Python library documentation for strptime behaviour.
specifies the systemd journal match used to filter the journal entries. See \fBjournalctl(1)\fR and \fBsystemd.journal-fields(7)\fR for matches syntax and more details on special journal fields. This option is only valid for the \fIsystemd\fR backend.
Similar to actions [Init] section enables filter-specific settings. All parameters specified in [Init] section can be redefined or extended in \fIjail.conf/jail.local\fR.
At the moment it is maintained and further developed by Yaroslav O. Halchenko <debian@onerussian.com>, Daniel Black <daniel.subs@internode.on.net> and Steven Hiscocks <steven-fail2ban@hiscocks.me.uk> along with a number of contributors. See \fBTHANKS\fR file shipped with Fail2Ban for a full list.
