It looks like this was reported in LP:1744296 and is supposed to have been fixed for Bionic.
** Changed in: ubuntu-fan (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to ubuntu-fan in Ubuntu. https://bugs.launchpad.net/bugs/2044428 Title: fanctl should exit 0 if interface is already configured Status in ubuntu-fan package in Ubuntu: Invalid Bug description: Hi, This is output from a `juju run` of `ifdown ens5; ifup ens5`: | - MachineId: "4" | ReturnCode: 1 | Stderr: | | Killed old client process | Internet Systems Consortium DHCP Client 4.3.3 | Copyright 2004-2015 Internet Systems Consortium. | All rights reserved. | For info, please visit https://www.isc.org/software/dhcp/ | | Corrupt lease file - possible data loss! | Listening on LPF/ens5/0a:c8:aa:2d:4d:2c | Sending on LPF/ens5/0a:c8:aa:2d:4d:2c | Sending on Socket/fallback | DHCPRELEASE on ens5 to 172.31.0.1 port 67 (xid=0x3575bf41) | run-parts: /etc/resolvconf/update-libc.d/squid exited with return code 3 | run-parts: /etc/resolvconf/update.d/libc exited with return code 1 | sudo: unable to resolve host ip-172-31-8-162: Connection refused | Internet Systems Consortium DHCP Client 4.3.3 | Copyright 2004-2015 Internet Systems Consortium. | All rights reserved. | For info, please visit https://www.isc.org/software/dhcp/ | | Listening on LPF/ens5/0a:c8:aa:2d:4d:2c | Sending on LPF/ens5/0a:c8:aa:2d:4d:2c | Sending on Socket/fallback | DHCPDISCOVER on ens5 to 255.255.255.255 port 67 interval 3 (xid=0x811b3e7f) | DHCPREQUEST of 172.31.8.162 on ens5 to 255.255.255.255 port 67 (xid=0x7f3e1b81) | DHCPOFFER of 172.31.8.162 from 172.31.0.1 | DHCPACK of 172.31.8.162 from 172.31.0.1 | run-parts: /etc/resolvconf/update-libc.d/squid exited with return code 3 | run-parts: /etc/resolvconf/update.d/libc exited with return code 1 | bound to 172.31.8.162 -- renewal in 1536 seconds. | /usr/sbin/fanctl: fan-252: already configured | run-parts: /etc/network/if-up.d/ubuntu-fan exited with return code 1 | Stdout: | | auto ens5 | iface ens5 inet6 dhcp | /usr/sbin/fanctl: /etc/network/fan:40 172.31.0.0/16 252.0.0.0/8 -- failed err=1 | Failed to bring up ens5. Unfortunately, it causes ifup to fail because fan interface already exists. ubuntu@ip-172-31-43-199:/etc/network$ apt-cache policy ubuntu-fan ubuntu-fan: Installed: 0.12.8~16.04.3 Candidate: 0.12.8~16.04.3 Version table: *** 0.12.8~16.04.3 500 500 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages 100 /var/lib/dpkg/status 0.9.0 500 500 http://gb.archive.ubuntu.com/ubuntu xenial/main amd64 Packages To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-fan/+bug/2044428/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp