Ubuntu 17.04 ships with netbase 5.4, which removes a number of protocols from /etc/services. One of these is imap3 (220/tcp) which is used by several entries in /etc/fail2ban/jail.conf. This led to the following messages in /var/log/fail2ban.log:
iptables -w -I INPUT -p tcp -m multiport --dports smtp,465,submission,imap3,imaps,pop3,pop3s -j f2b-postfix-sasl -- stdout: b''
2017-04-13 21:37:04,274 fail2ban.action [2565]: ERROR iptables -w -N f2b-postfix-sasl
iptables -w -A f2b-postfix-sasl -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports smtp,465,submission,imap3,imaps,pop3,pop3s -j f2b-postfix-sasl -- stderr: b"iptabl
es v1.6.0: invalid port/service `imap3' specified\nTry `iptables -h' or 'iptables --help' for more information.\n"
2017-04-13 21:37:04,278 fail2ban.action [2565]: ERROR iptables -w -N f2b-postfix-sasl
iptables -w -A f2b-postfix-sasl -j RETURN
iptables -w -I INPUT -p tcp -m multiport --dports smtp,465,submission,imap3,imaps,pop3,pop3s -j f2b-postfix-sasl -- returned 2
2017-04-13 21:37:04,279 fail2ban.actions [2565]: ERROR Failed to start jail 'postfix-sasl' action 'iptables-multiport': Err
or starting action
The fail2ban package should be updated to remove references to the removed protocols.
ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: fail2ban 0.9.6-1
ProcVersionSignature: Ubuntu 4.10.0-19.21-generic 4.10.8
Uname: Linux 4.10.0-19-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.4-0ubuntu4
Architecture: amd64
CurrentDesktop: Unity:Unity7
Date: Fri Apr 14 12:11:57 2017
InstallationDate: Installed on 2016-12-27 (108 days ago)
InstallationMedia: Ubuntu-Server 16.10 "Yakkety Yak" - Release amd64 (20161012.1)
PackageArchitecture: all
SourcePackage: fail2ban
UpgradeStatus: Upgraded to zesty on 2017-04-14 (0 days ago)
Status changed to 'Confirmed' because the bug affects multiple users.