I had a bad time.
I ran a do-release-upgrade on one of my Amazon EC2 instances to try and upgrade it from 14.04 (Trusty) to 16.04 (Xenial). After the update and a reboot the box refused to come back up. When I detached the drive and attached it to another to check syslog I found this:
/sbin/dhclient -1 -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -I -df /var/lib/dhcp/dhclient6.eth0.leases eth0
Usage: dhclient [-4|-6] [-SNTP1dvrx] [-nw] [-p <port>] [-D LL|LLT]
[-s server-addr] [-cf config-file] [-lf lease-file]
[-pf pid-file] [--no-pid] [-e VAR=val]
[-sf script-file] [interface]
Failed to bring up eth0.
Oh good, it forgot how to eth0.
I spent about four hours figuring out how to fix it:
apt update
apt -y upgrade
cat << EOF > /etc/update-manager/release-upgrades.d/unauth.cfg
[Distro]
AllowUnauthenticated=yes
EOF
apt install -y network-manager
do-release-upgrade
apt update
apt -y upgrade
systemctl enable systemd-networkd
systemctl enable systemd-resolved
dpkg-reconfigure resolvconf
apt-get -y autoremove
rm /etc/update-manager/release-upgrades.d/unauth.cfg
reboot
- Make sure you are up to date first.
- Some packages (python3) complain that they are unauthenticated. Feel free to skip this if you want.
- Install the network-manager
- Leap of faith... do the upgrade
- Finish the upgrade by installing the rest of the packages.
- Enable the systemd network daemon and resolver daemon
- Reconfigure resolvconf so you can dns
- Get rid of the unauth.cfg file you created
- Reboot and pray.
Thanks to these three links for the solutions (I just put them together):
- https://askubuntu.com/a/426121
- https://askubuntu.com/a/769239
- http://willhaley.com/blog/resolvconf-dns-issue-after-ubuntu-xenial-upgrade/