[Bug 1771236] Re: forced use of systemd-networkd interferes with ifupdown in 18.04

[Wes]

There are plenty of examples, some of them bespoke 3rd party things.  An
equally large issue though are legacy technicians who aren't familiar
with systemd's way of doing things yet (I've been trying to get them up
to speed though).

But the crux is if returning to ifupdown is offered as an option, then
it needs to work as expected.  If there's more to reverting to the old
way than merely 'apt install ifupdown' then the documentation and config
file comments referring to this needs to be updated to outline these
steps.  If a sysadmin disables systemd-networkd, it should stay
disabled.

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1771236

Title:
  forced use of systemd-networkd interferes with ifupdown in 18.04

Status in systemd package in Ubuntu:
  Incomplete

Bug description:
  For several reasons, we are not able to use netplan nor systemd-
  networkd due to legacy applications that expect ifupdown's pre-up and
  post-up script mechanism.  The documentation around 18.04's
  (premature, I feel) wholesale adoption of netplan claims that one can
  revert to old behaviour by merely installing ifupdown (amongst
  assertions that netplan will never offer a mechanism for configuring
  pre-up and post-up actions even for network managers that support
  them).

  However when ifupdown is installed, systemd-networkd still tries to
  manage interfaces.  If you 'systemctl disable systemd-networkd', upon
  next reboot it is automatically re-enabled.  We tried disabling any
  systemd units even remotely related to networking and yet systemd-
  networkd still runs.  If it hasn't been configured, it tries to DHCP.
  On networks that don't provide DHCP this results in a stupendously
  long stall during boot.  Currently it appears to be impossible to tell
  systemd-networkd not to run in a clean manner that won't get reverted
  on package upgrades.

  I sincerely hope this is is a bug/oversight and not intentional.  We
  need to be able to disable systemd-networkd properly.

  Thanks

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1771236/+subscriptions