I may be reading something incorrectly but it doesn't look like the enabled fail2ban filters in the container are working properly according to the logs on a fresh docker install.
2017-09-14 23:21:53,943 fail2ban.utils [266]: ERROR ip6tables -w -N f2b-nginx-http-auth
ip6tables -w -A f2b-nginx-http-auth -j RETURN
ip6tables -w -I INPUT -p tcp -m multiport --dports http,https -j f2b-nginx-http-auth -- stderr:
2017-09-14 23:21:53,943 fail2ban.utils [266]: ERROR -- stderr: "modprobe: can't change directory to '/lib/modules': No such file or directory"
2017-09-14 23:21:53,943 fail2ban.utils [266]: ERROR -- stderr: "ip6tables v1.6.1: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)"
2017-09-14 23:21:53,943 fail2ban.utils [266]: ERROR -- stderr: 'Perhaps ip6tables or your kernel needs to be upgraded.'
2017-09-14 23:21:53,944 fail2ban.utils [266]: ERROR -- stderr: "modprobe: can't change directory to '/lib/modules': No such file or directory"
2017-09-14 23:21:53,944 fail2ban.utils [266]: ERROR -- stderr: "ip6tables v1.6.1: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)"
2017-09-14 23:21:53,944 fail2ban.utils [266]: ERROR -- stderr: 'Perhaps ip6tables or your kernel needs to be upgraded.'
2017-09-14 23:21:53,944 fail2ban.utils [266]: ERROR -- stderr: 'Could not open socket to kernel: Address family not supported by protocol'
2017-09-14 23:21:53,944 fail2ban.utils [266]: ERROR ip6tables -w -N f2b-nginx-http-auth
ip6tables -w -A f2b-nginx-http-auth -j RETURN
ip6tables -w -I INPUT -p tcp -m multiport --dports http,https -j f2b-nginx-http-auth -- returned 1
2017-09-14 23:21:53,944 fail2ban.actions [266]: ERROR Failed to start jail 'nginx-http-auth' action 'iptables-multiport': Error starting action Jail('nginx-http-auth')/iptables-multiport
2017-09-14 23:21:53,981 fail2ban.utils [266]: ERROR ip6tables -w -N f2b-nginx-badbots
ip6tables -w -A f2b-nginx-badbots -j RETURN
ip6tables -w -I INPUT -p tcp -m multiport --dports http,https -j f2b-nginx-badbots -- stderr:
2017-09-14 23:21:53,982 fail2ban.utils [266]: ERROR -- stderr: "modprobe: can't change directory to '/lib/modules': No such file or directory"
2017-09-14 23:21:53,982 fail2ban.utils [266]: ERROR -- stderr: "ip6tables v1.6.1: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)"
2017-09-14 23:21:53,983 fail2ban.utils [266]: ERROR -- stderr: 'Perhaps ip6tables or your kernel needs to be upgraded.'
2017-09-14 23:21:53,983 fail2ban.utils [266]: ERROR -- stderr: "modprobe: can't change directory to '/lib/modules': No such file or directory"
2017-09-14 23:21:53,983 fail2ban.utils [266]: ERROR -- stderr: "ip6tables v1.6.1: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)"
2017-09-14 23:21:53,984 fail2ban.utils [266]: ERROR -- stderr: 'Perhaps ip6tables or your kernel needs to be upgraded.'
2017-09-14 23:21:53,984 fail2ban.utils [266]: ERROR -- stderr: 'Could not open socket to kernel: Address family not supported by protocol'
2017-09-14 23:21:53,985 fail2ban.utils [266]: ERROR ip6tables -w -N f2b-nginx-badbots
ip6tables -w -A f2b-nginx-badbots -j RETURN
ip6tables -w -I INPUT -p tcp -m multiport --dports http,https -j f2b-nginx-badbots -- returned 1
2017-09-14 23:21:53,985 fail2ban.actions [266]: ERROR Failed to start jail 'nginx-badbots' action 'iptables-multiport': Error starting action Jail('nginx-badbots')/iptables-multiport
2017-09-14 23:21:53,997 fail2ban.utils [266]: ERROR ip6tables -w -N f2b-nginx-botsearch
ip6tables -w -A f2b-nginx-botsearch -j RETURN
ip6tables -w -I INPUT -p tcp -m multiport --dports http,https -j f2b-nginx-botsearch -- stderr:
2017-09-14 23:21:53,998 fail2ban.utils [266]: ERROR -- stderr: "modprobe: can't change directory to '/lib/modules': No such file or directory"
2017-09-14 23:21:53,998 fail2ban.utils [266]: ERROR -- stderr: "ip6tables v1.6.1: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)"
2017-09-14 23:21:53,999 fail2ban.utils [266]: ERROR -- stderr: 'Perhaps ip6tables or your kernel needs to be upgraded.'
2017-09-14 23:21:53,999 fail2ban.utils [266]: ERROR -- stderr: "modprobe: can't change directory to '/lib/modules': No such file or directory"
2017-09-14 23:21:53,999 fail2ban.utils [266]: ERROR -- stderr: "ip6tables v1.6.1: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)"
2017-09-14 23:21:54,000 fail2ban.utils [266]: ERROR -- stderr: 'Perhaps ip6tables or your kernel needs to be upgraded.'
2017-09-14 23:21:54,000 fail2ban.utils [266]: ERROR -- stderr: 'Could not open socket to kernel: Address family not supported by protocol'
2017-09-14 23:21:54,000 fail2ban.utils [266]: ERROR ip6tables -w -N f2b-nginx-botsearch
ip6tables -w -A f2b-nginx-botsearch -j RETURN
ip6tables -w -I INPUT -p tcp -m multiport --dports http,https -j f2b-nginx-botsearch -- returned 1
2017-09-14 23:21:54,000 fail2ban.actions [266]: ERROR Failed to start jail 'nginx-botsearch' action 'iptables-multiport': Error starting action Jail('nginx-botsearch')/iptables-multiport