[Bug 1881832] Re: Ubuntu server 20.04 fails to get IP address from DHCP server (no network connectivity)

[Anthony Bush]

*** This bug is a duplicate of bug 1882162 ***
    https://bugs.launchpad.net/bugs/1882162

@slyon - I use unraid here, and if I modify the VM configuration at all
(I just mounted an unraid share through unraid's VM manager, and
rebooted my Ubuntu Server - no IP address). I made no changes beyond
that, which seems odd, (and I understand that unraid's VM manager is not
applicable per-say here) just figured I would provide the additional
information. Seems to happen anytime the configuration changes - the
device name in Ubuntu is modified, but the netplan configuration keeps
the original ethernet device name from the install. In this specific
case, 00-installer-config.yaml has the device name as enp1s0, but the
correct device name is now enp3s0. Luckily, I know how to fix, but its
quite impactful.

IMHO, the issue is the installer's eth device path, which clearly
changes later on in the lifecycle of the VM but netplan doesn't
recognise nor modify it's config.

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https://bugs.launchpad.net/bugs/1881832

Title:
  Ubuntu server 20.04 fails to get IP address from DHCP server (no
  network connectivity)

Status in netplan.io package in Ubuntu:
  Invalid
Status in subiquity package in Ubuntu:
  New

Bug description:
  Ubuntu 20.04 server amd64, running as virtual machine on FreeNAS-11.3-U3.2.
  Network interface was configured with driver VirtIO, and network interface is bridged at FreeNAS.

  The issue is that I have DHCP server in my LAN and Ubuntu installer
  gets IPv4 address and applies updates from internet. Install process
  is OK. Once installation is finished, reboot is required but Ubuntu
  will start but  no IP address is assigned to enp0s4 interface, so
  Ubuntu 20.04 server has no network connectivity. I can manually force
  IP address allocation with command "sudo dhclient enp0s4" and it works
  but that is just a workaround. IP address should be allocated
  automatically during server boot...

  I have older Ubuntu machines on the same FreeNAS box and those work
  fine, so I assume there is a bug in Ubuntu 20.04 and DHCP client is
  broken or not reliable... :-( Some problem in netplan utility??

  I tried to install fresh 18.04.4 to my FreeNAS box and I see the same
  problem, no IP address is assigned during boot. That is strange
  because old installation of 18.04 from the past works fine.

  I tried to install 20.04 to VMware ESXi 6.7 and I see the same
  problem, no IP address is assigned to the new instance (install is OK,
  but after restart, no network connectivity, "dhclient ensp0s4" is
  working fine).

  Summary is that I see similar problem on fresh installs of 20.04 and
  18.04, FreeNAS or ESXi. I can connect instances with "dhclient
  enp0s4", so it looks like DHCP server works fine and there is no
  problem on LAN...

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