[Bug 1823871] Re: After unattended-upgrade of systemd IP configuration removed from interfaces

[Domonkos Tomcsanyi]

I have followed the instructions in the /etc/network/interfaces file to
ditch netplan and use ifupdown:

# To re-enable ifupdown on this system, you can run:
#    sudo apt install ifupdown

As an extra measure I have removed netplan packages completely:

~# grep netplan .bash_history
apt remove nplan netplan.io

I have opened the bug against systemd, because I think it is the one responsible for the issue, but I could be wrong. It could be the unattended-upgrades package with the combination of systemd as well, or something different. I have written down the way my network configuration works so that enough information of my system is available - especially in this case where networking itself seems to have a hiccup.
Weirdly enough my virtual bridge (configured via the same /etc/network/interfaces file) supporting my VMs running on the server has not lost its IP configuration. This + Joi's experience indicate to me that this is not an issue of how the network configuration is applied on the server, it is an issue of something on a lower level possibly, and the loss of network connection is just an inconvenient result, and not the issue itself.

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Title:
  After unattended-upgrade of systemd IP configuration removed from
  interfaces

Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  Info:
  Ubuntu Server 18.04 LTS, 4.15.0-43-generic, fresh installation (December, 2018).
  HP DL380 server

  I had this issue already twice in the past couple of months. After unattended upgrade of systemd my server's public IP address is removed from the interface.
  I statically configure the IP address using the interfaces file. I have opted out of the YML based network configuration. This is my apt history log:

  Start-Date: 2019-04-09  06:15:01
  Commandline: /usr/bin/unattended-upgrade
  Upgrade: systemd-sysv:amd64 (237-3ubuntu10.13, 237-3ubuntu10.19)
  End-Date: 2019-04-09  06:15:07

  Start-Date: 2019-04-09  06:15:12
  Commandline: /usr/bin/unattended-upgrade
  Upgrade: udev:amd64 (237-3ubuntu10.13, 237-3ubuntu10.19), libudev1:amd64 (237-3ubuntu10.13, 237-3ubuntu10.19)
  End-Date: 2019-04-09  06:15:56

  Start-Date: 2019-04-09  06:15:59
  Commandline: /usr/bin/unattended-upgrade
  Upgrade: libsystemd0:amd64 (237-3ubuntu10.13, 237-3ubuntu10.19), libpam-systemd:amd64 (237-3ubuntu10.13, 237-3ubuntu10.19), systemd:amd64 (237-3ubuntu10.13, 237-3ubuntu10.19), libnss-systemd:amd64 (237-3ubuntu10.13, 237-3ubuntu10.19)
  End-Date: 2019-04-09  06:16:15

  
  After that my server was unavailable from the Internet. When I logged in via out of band management and simply brought down and up the interface everything went back to normal. As said above this is the second time I had this issue. Last time it was unattended upgrades and it was systemd again.

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