config f2b for Ubuntu or Debian

etc/fail2ban/jail.d/dovecot.conf

@@ -2,4 +2,4 @@
 enabled = true
 port    = imap2,imap3,imaps,pop3,pop3s
 filter  = dovecot
-logpath = /var/log/mail.log tail
+

etc/fail2ban/jail.d/exim-hard.conf

@@ -2,6 +2,7 @@
 enabled  = true
 port     = smtp,ssmtp,imap2,imap3,imaps,pop3,pop3s,submission
 filter   = exim-hard
+backend  = auto
 logpath  = /var/log/exim4/rejectlog tail
 maxretry = 1
 bantime  = 86400

etc/fail2ban/jail.d/exim-ratelimit.conf

@@ -3,6 +3,7 @@ enabled  = true
 port     = smtp,ssmtp,imap2,imap3,imaps,pop3,pop3s,submission
 filter   = exim-ratelimit
 action   = mail-ratelimit
+backend  = auto
 logpath  = /var/log/exim4/rejectlog tail
 maxretry = 1
 findtime = 60

etc/fail2ban/jail.d/exim.conf

@@ -2,4 +2,5 @@
 enabled  = true
 port     = smtp,465,submission
 filter   = exim
+backend  = auto
 logpath  = /var/log/exim4/rejectlog tail

install.sh

@@ -129,7 +129,7 @@ install --owner=Debian-exim --group=Debian-exim --mode=640 /dev/null /etc/exim4/
 cp etc/exim4/* /etc/exim4/
 if [ $os_codename = jammy ]; then
   cp /etc/exim4/exim4-jammy.conf /etc/exim4/exim4.conf
-elif [ $os_codename != bookworm ]; then
+elif [ $os_codename = bookworm ]; then
   cp /etc/exim4/exim4-bookworm.conf /etc/exim4/exim4.conf
 else
   echo "WARNING: Unexpected OS codename. This should never happen due to previous checks."
@@ -217,6 +217,12 @@ fi
 if [[ -d /etc/fail2ban/ ]]; then
   chmod 644 etc/fail2ban/*/*.conf
   cp -a etc/fail2ban/* /etc/fail2ban/
+  if [ $os_codename = bookworm ]; then
+    echo "backend = systemd" >> /etc/fail2ban/jail.d/dovecot.conf
+  elif [ $os_codename = jammy ]; then
+    echo "backend = auto" >> /etc/fail2ban/jail.d/dovecot.conf
+    echo "logpath = /var/log/mail.log tail" >> /etc/fail2ban/jail.d/dovecot.conf
+  fi
 else
   echo
   echo "fail2ban not installed, skipping fail2ban email configs."