\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]:
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.
.TP
.Bdbpurgeage
Database purge age in seconds. Default: 86400 (24hours)
This sets the age at which bans should be purged from the database.
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.
filename(s) of the log files to be monitored, separated by new lines. Globs -- paths containing * and ? or [0-9] -- can be used however only the files that exist at start up matching this glob pattern will be considered.
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.
action(s) from \fI/etc/fail2ban/action.d/\fR without the \fI.conf\fR/\fI.local\fR extension. Arguments can be passed to actions to override the default values from the [Init] section in the action file. Arguments are specified by:
.RS
.RS
[name=value,name2=value,name3="values,values"]
.RE
Values can also be quoted (required when value includes a ","). More that one action can be specified (in separate lines).
command that is executed to determine if the current candidate IP for banning should not be banned. IP will not be banned if command returns successfully (exit code 0).
Like ACTION FILES, tags like <ip> are can be included in the ignorecommand value and will be substituted before execution. Currently only <ip> is supported however more will be added later.
backend to be used to detect changes in the logpath. 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. 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.
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.
.TP
.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 [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:
.TP
\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. The filter [Init] section is limited to the following options:
.TP
\fBmaxlines\fR
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.
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.
