checkmk monitoring script for fail2ban

In order to have a lokal check for checkmk to monitor fail2ban jails, here is a small check script:

#! /bin/bash

declare -i RETCODE=0
declare -i EXITCODE=0

# you can define the list of jails to monitor here
#declare -r JAILS="exchange tsg nextcloud bruteforce"
# or automatically monitor all jails
declare -r JAILS=$(fail2ban-client status | sed '/Jail list:/!d; s/^.*Jail list:\s*//g; s/,\s*/ /g')

for jail in $JAILS; do

    fail2ban-client status ${jail} > /tmp/fail2ban-${jail}.status 2>&1

    RETCODE=$?
    EXITCODE=0

    if [ $RETCODE -gt 0 ]; then
        EXITCODE=2
    fi

    FILELIST=$(sed '/File list:/!d;s/^.*:\s*//g;' /tmp/fail2ban-${jail}.status)
    STATUSFILECONT=$(sed 's/|//g;s/`//g' /tmp/fail2ban-${jail}.status)

    if [ $EXITCODE -eq 0 ] ; then
        if [ -n "$FILELIST" ]; then
            statustxt="OK"
            txt="$(echo $STATUSFILECONT)  "
        else
            EXITCODE=1
            txt="no log files listed: $(echo $STATUSFILECONT)"
        fi
        perf=$(sed '/^ *|/!d;/:/!d;/File list:/d;s/^.*- //g;s/ /_/g;s/:\s*/=/g;s/$/|/g;s/=|/=0|/g;' /tmp/fail2ban-${jail}.status)
    else
        statustxt="CRITICAL"
        perf=""
        txt="$(echo $STATUSFILECONT)  "
    fi

    echo "$EXITCODE fail2ban-${jail} "$(echo $perf | sed 's/ //g;s/|$//g')" $statustxt - $txt"
done

Just save it to /usr/lib/check_mk_agent/local/check_fail2ban.sh, make the file executable and it will create one check per jail.

Update:

fail2ban
checkmk