Warning: upgrading Devuan jessie brings in a new version of
ifupdown entangled with Systemd. Here is the message:
------- beginning of message ----------
ifupdown (0.8.1) unstable; urgency=medium

The /etc/default/networking file is now read even when systemd is used,
although its use is not recommended.

-- Guus Sliepen <guus@???> Wed, 02 Dec 2015 23:25:41 +0100

ifupdown (0.8) unstable; urgency=medium

Ifupdown now comes with a systemd service file. Any options specified in
/etc/default/networking will no longer be used. If you are using
CONFIGURE_INTERFACES=no, then run "systemctl disable networking" instead.
If you are using EXCLUDE_INTERFACES, then edit
/etc/network/interfaces and
remove those interfaces from any "auto" keywords.

Ifupdown will now be more strict when errors occur, and will also
properly
return a non-zero exit code when (de)configuring an interface fails.
Please
ensure your /etc/network/interfaces is correct and that your
interfaces can
be brought up and down without errors, especially during system startup.

Ifupdown now has more fine-grained locking, allowing concurrent calls of
ifup and ifdown. It is also allowed to call ifup and ifdown from a
(pre-)up
or (post-)down line from /etc/network/interfaces, as long as no recursion
occurs.

You can now use the "inherits" keyword to copy settings from another
interface stanza.

RFC 4361 DDNS support is now enabled by default for inet dhcp
interfaces if
isc-dhcp-client is installed.

-- Guus Sliepen <guus@???> Sun, 22 Nov 2015 21:19:44 +0100

systemd (220-7) unstable; urgency=medium

   * The mechanism for providing stable network interface names changed.
     Previously they were kept in /etc/udev/rules.d/70-persistent-net.rules
     which mapped device MAC addresses to the (arbitrary) name they got when
     they first appeared (i. e. mostly at the time of installation). As this
     had several problems and is not supported any more, this is 
deprecated in
     favor of the "net.ifnames" mechanism. With this most of your network
     interfaces will get location-based names. If you have ifupdown, 
firewall,
     or other configuration that relies on the old names, you need to update
     these by Debian 10/Ubuntu 18.04 LTS, and then remove
     /etc/udev/rules.d/70-persistent-net.rules. Please see
     /usr/share/doc/udev/README.Debian.gz for details about this.

-- Martin Pitt <mpitt@???> Mon, 15 Jun 2015 15:30:29 +0200

--------- end of message -------------

The following packages interdepend with ifupdown: udev, libudev1. I had
to lock the version of all three.

I was alarmed by the message but don't know if upgrading these 3
packages is really harmfull.

     Didier