ifupdown is actually behaving correctly in this case. It's likely that cloud-initramfs-tools should be marking the interface "iface foo inet[6] manual" in every case, since that's the indicator that seems to prevent ifdown from downing the interface.
When I had it do that, what I then found was that we had gotten to "reached shutdown target", and the system was then having timeouts in systemd watchdogs. Looking at it with systemd's debug shell, /media /root-ro (the iscsi volume) has been unmounted, and /media/root-rw (the overlayfs) is still mounted. Interestingly, the last few things are: [ OK ] Unmounted /media/root-rw. [ OK ] Reached target Unmount All Filesystems. [ OK ] Stopped target Local File Systems (Pre). Stopped Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progress polling... [ OK ] Stopped Remount Root and Kernel File Systems [ OK ] Stopped Create Static Device Nodes in /dev. [ OK ] Reached target Shutdown 5 seconds later is the "connection 1:0: ping timeout of 5 secs expired, .... and / is still (or is that "again") mounted on overlayfs rw,relatime,lowerdir=/media/root-ro,upperdir=/media/root-rw//overlay,workdir=/media/root-rw//overlay-workdir And then there is the collection of "INFO: task systemd:1 blocked for more than 120 seconds." log entries on the console. ** Changed in: ifupdown (Ubuntu) Assignee: LaMont Jones (lamont) => (unassigned) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1629972 Title: networking stop incorrectly disconnects from (network) root filesystem To manage notifications about this bug go to: https://bugs.launchpad.net/maas/+bug/1629972/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs