networking – Ubuntu 20.04 loses network in AWS after updates 28 october

28 october I run a series of normal updates on one of my Amazon-EC2 instances. For some reason it locked up and I had to reboot it. It got up but it never got any network again. So after a lot of troubleshooting I restored it from an old snapshot. After updating it (that went smoothly) I rebooted as expected and it got up, but without network connectivity. This is quite annoying.

Is this a known problem? When I look in dpkg.log in the instance that crashed first, the following packages were updated (filtered dump from dpkg.log). I see quite a lot of network-related stuff there.

upgrade ca-certificates:all 20190110ubuntu1.1 20201027ubuntu0.20.04.1
upgrade distro-info-data:all 0.43ubuntu1.1 0.43ubuntu1.2
upgrade accountsservice:amd64 0.6.55-0ubuntu12~20.04.1 0.6.55-0ubuntu12~20.04.2
upgrade libaccountsservice0:amd64 0.6.55-0ubuntu12~20.04.1 0.6.55-0ubuntu12~20.04.2
upgrade bind9-dnsutils:amd64 1:9.16.1-0ubuntu2.3 1:9.16.1-0ubuntu2.4
upgrade bind9-libs:amd64 1:9.16.1-0ubuntu2.3 1:9.16.1-0ubuntu2.4
upgrade bind9-host:amd64 1:9.16.1-0ubuntu2.3 1:9.16.1-0ubuntu2.4
upgrade libplymouth5:amd64 0.9.4git20200323-0ubuntu6 0.9.4git20200323-0ubuntu6.1
upgrade plymouth-theme-ubuntu-text:amd64 0.9.4git20200323-0ubuntu6 0.9.4git20200323-0ubuntu6.1
upgrade plymouth:amd64 0.9.4git20200323-0ubuntu6 0.9.4git20200323-0ubuntu6.1

My (admittedly bad) forensics says that something goes wrong in cloud-init. That init is necessary as an instance gets a new IP every time it boots (it has a static IP but that is routed to the dynamic one).

I see two ways forward: Either I restore from my dump again and try to hold the packages above somehow or I find a way to fix the resulting network issue without having access to the live machine (as it has no network), I do have access to the file system when the machine is taken down though.

Any ideas or help appreciated! Thank you!