66

Starting sometime around Ubuntu 18.04, the Ubuntu devs stopped using the classic /etc/init.d/networking and /etc/network/interfaces method of configuring the network and switched to some thing called netplan. This has made a lot of people very angry and been widely regarded as a bad move. Is it possible to remove netplan and use the correct /etc/network/interfaces method for configuring the network?

19
  • 3
    Why not just configure with netplan? In most situations, it is pretty straightforward.
    – chili555
    May 3 '18 at 20:00
  • 4
    @chili555 It may be that I just have to accept the change and learn something new. I'd just like to know if it is trivial to revert back to the way it should be. Much like systemd, I understand that disruptive change can sometimes be beneficial and be embraced. However, this is certainly not one of those times when the change was needed or beneficial.
    – jdgregson
    May 3 '18 at 20:06
  • 1
    It is not trivial and not easily reversible in case of error. If you'd like to live dangerously, I'll be happy to propose an answer. On the other hand, we can configure netplan in a couple of minutes. Which do you prefer? PS- I don't pretend to fully understand how netplan, to the exclusion of /etc/network/interfaces, fits in to the larger systemd picture. All I can do is trust that those who introduced the change do know why it's a better fit.
    – chili555
    May 3 '18 at 20:25
  • 2
    Or, just properly configure netplan and be done.
    – chili555
    May 3 '18 at 21:06
  • 1
    @chili555 Netplan doesn't support virtual network interfaces. See here: askubuntu.com/questions/990825/virtual-interface-in-netplan Jan 28 '19 at 8:12
61

The following procedure works for Ubuntu 18.04 (Bionic Beaver)

I. Reinstall the ifupdown package:

# apt-get update
# apt-get install ifupdown

II. Configure your /etc/network/interfaces file with configuration stanzas such as:

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

allow-hotplug enp0s3
auto enp0s3
iface enp0s3 inet static
  address 192.168.1.133
  netmask 255.255.255.0
  broadcast 192.168.1.255
  gateway 192.168.1.1
  # Only relevant if you make use of RESOLVCONF(8)
  # or similar...
  dns-nameservers 1.1.1.1 1.0.0.1

III. Make the configuration effective (no reboot needed):

# ifdown --force enp0s3 lo && ifup -a
# systemctl unmask networking
# systemctl enable networking
# systemctl restart networking

IV. Disable and remove the unwanted services:

# systemctl stop systemd-networkd.socket systemd-networkd \
networkd-dispatcher systemd-networkd-wait-online
# systemctl disable systemd-networkd.socket systemd-networkd \
networkd-dispatcher systemd-networkd-wait-online
# systemctl mask systemd-networkd.socket systemd-networkd \
networkd-dispatcher systemd-networkd-wait-online
# apt-get --assume-yes purge nplan netplan.io

Then, you're done.

Note: You MUST, of course, adapt the values according to your system (network, interface name...).

V. DNS Resolver

Because Ubuntu Bionic Beaver (18.04) make use of the DNS stub resolver as provided by SYSTEMD-RESOLVED.SERVICE(8), you SHOULD also add the DNS to contact into the /etc/systemd/resolved.conf file. For instance:

....
DNS=1.1.1.1 1.0.0.1
....

and then restart the systemd-resolved service once done:

# systemctl restart systemd-resolved

The DNS entries in the ifupdown INTERFACES(5) file, as shown above, are only relevant if you make use of RESOLVCONF(8) or similar.

17
  • 18
    Well, f*** them. Just apt-get install when you've got no network configuration. What a brilliant idea, Canonical.
    – Velkan
    Aug 3 '18 at 6:47
  • 1
    @Velkan You can always pre-configure your network with netplan then switch back to ifupdown later on ;) But I agreed with you. Somehow canonical take bad decisions. For instance, they break softwares that rely on ifupdown for networking configuration (no provider for netplan). This is the case for our control panel software (stable serie) where we do not want add new network configuration provider...
    – Nuxwin
    Aug 5 '18 at 9:58
  • 4
    @StephenBoston I totally agree with you. However, even if Canonical try to go ahead by introducing new technology, it could do this in less invasive manner. I mean, the choice should be left to end user. For workstations, the change from ifupdown to netplan is surely not a big deal but when you have to deal with Ubuntu servers, that's another story because most stable softwares doesn't necesserely provide adapters... That has been the same story for systemd. I've to deal with both Debian and Ubuntu everydays. The problem with Ubuntu is that they don't care much about backward compatibility.
    – Nuxwin
    Sep 1 '18 at 5:59
  • 1
    Also, if you use dns-domain and dns-searchin the interfaces file, you should configure the Domains parameter in resolved.conf, I think? Anyway, great job putting that all together here, probably saved me a lot of time :)
    – OttoEisen
    Dec 16 '18 at 16:26
  • 1
    @Nuxwin man for resolved.conf said that 'DNS=' is "A space-separated list" Mar 24 '19 at 7:40
12

The Netplan team has posted an official answer on their FAQ here:

How to go back to ifupdown

...

On a running system, netplan can be removed by installing ifupdown and configuring /etc/network/interfaces manually as users have done before.

At install time, a user can opt to use ifupdown by preseeding netcfg/do_not_use_netplan=true. This is done by adding the preseed line to the command line when booting the installation media (i.e. at install media boot menu, press F6, type ‘e’, and add to the command line).

See Nuxwin's answer for more complete instructions.

1
  • This appears to be ignored by the 18.04.4 installer. I tried putting this option both before and after the --- that ends the command line initially presented (on separate attempts, of course) and always end up with netplan. I may need to try installed 16.04 and doing a dist upgrade just to get what I want. Mar 31 '20 at 10:19
6

The answer of Nuxwin is great and almost complete, I'd just add the lines:

rm /etc/resolv.conf
ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf

This will make sure that the resolver can be updated by the DHCP-client, like it was before when using interfaces.

(I would have added this as a comment but somehow one need 50 reputation to post a comment)

2
  • Upvoting to get you to 50 rep.
    – jdgregson
    Nov 18 '20 at 19:03
  • @Nmath, thanks for the hints, I've edited my post.
    – ChrisTG74
    Nov 22 '20 at 10:25
4

Why not just configure with netplan?

Well, as it is configured in 18.04-Desktop, it is a single line handing over control to all interfaces to NetworkManager.

While that is probably suitable for 95% of users, remember that NetworkManager is only run once you are logged in to a session.

Should you want your machine to act as a server/desktop, for example start serving files to local machines, acting as VNP server, etc... or anything "fancy" before anyone is ever logged in, just by the simple fact it is on, you will have trouble with how it is configured in standard 18.04-Desktop.

Of course, the alternative would be to use the server-Netplan configuration, which, as far as I have read (not checked by myself), hands control over to systemd-networkd instead. In this case you'd better learn how systemd does things as a replacement of the old System V init.

Should you go this path, you still have to make change to the netplan yaml, since on a desktop version the control is given to NetworkManager.

6
  • 4
    At least one reason exists: Netplan does not support openvswitch.
    – Kamilion
    Aug 31 '18 at 18:07
  • 6
    netplan does not support IP aliases (eth0:0 style). I can't believe how such thing could find its way into Ubuntu server! Oct 11 '18 at 12:30
  • Because my netplan directories is empty !
    – dsgdfg
    Jan 16 '19 at 12:47
  • 2
    NetworkManager service starts pretty early and does not require a session or a logged-in user.
    – thaller
    Oct 23 '19 at 21:04
  • Because netplan is not ready for production, with the slightest network problems the server will go into an endless load. Dec 8 '20 at 10:38
2

Why not just remove netplan:

$ sudo apt remove netplan
$ rm -rf /etc/netplan

Once for all!

1
  • Assuming you've never successfully connected the server to the network before to install alternate methods of configuring the network, does this leave you completely unable to configure networking? It is there a built in fallback method?
    – jdgregson
    May 2 at 17:53
1

The key is knowing that cloud.init is the real control program.
That being said the line in the netplan config file "optional: true" is mandatory.
Knowing that made it easy.

I just removed 01-network-manager-all.yaml and copied it to /root/save/. Then put a known good config in place instead of it, 50-cloud-init.yaml: its contents follow:

network:
  version: 2
  renderer: networkd
  ethernets:
    eports:
      match: 
        name: enp*
        optional: true
  bonds:
    bond0:
      interfaces: [eports]
      addresses: [192.168.2.5/24]
      gateway4: 192.168.2.1
      nameservers:
        addresses: [127.0.0.1, 8.8.4.4]          
      parameters:
        mode: 0          
        mii-monitor-interval: 100

Then reboot and it should be working fine.

The known good config came from Configure bonded 802.3ad network using netplan on Ubuntu 18.04.

1
  • 1
    The question here is how to switch back to ifupdown ;) In future, you should try to answer the questions without polluting them, even through it is not always easy to stick to initial subject ;)
    – Nuxwin
    Sep 1 '18 at 6:09
0

According to this answer, the solution is to remove all operational .yaml files: Ubuntu 17.10 disable netplan

I wouldn’t remove anything without backing up. We can do so easily by simply moving the files aside. First, locate the files:

sudo updatedb
locate netplan | grep yaml

On my 18.04 system, it appears that the only operational file is /etc/netplan/01-network-manager-all.yaml. Let’s move it:

mkdir ~/netplan
sudo mv /etc/netplan/01-network-manager-all.yaml  /home/user/netplan

...where user is your user name.

Now check to make sure the file is truly gone:

ls /etc/netplan

Now make your additions to /etc/network/interfaces as required.

Reboot.

Any improvement?

Footnote: The exact process to do this is hard to find. We may need to refine a bit as we go.

10
  • I'll have to try that and see how it goes. The only other question would be how to apply the changes without rebooting. In the past you could use ifup/ifdown, /etc/init.d/networking restart, service networking restart, and the systemd methods, like systemctl restart networking, systemctl restart Network-Manager.service etc, but none of these were possible for me after installing Ubuntu 18.04.
    – jdgregson
    May 3 '18 at 22:05
  • What is the result of: sudo ip link set eth0 down followed by: sudo ifup -v eth0 Of course, substitute your interface for the mythical eth0.
    – chili555
    May 3 '18 at 23:01
  • ifupdown is not installed by default, so when you call ifup it just tells you how to install it. However, sudo ip link set eth0 down followed by sudo ip link set eth0 up does turn the interface off and back on.
    – jdgregson
    May 3 '18 at 23:27
  • Awesome! So you are solved and all set?
    – chili555
    May 3 '18 at 23:46
  • Careful, not all *.yaml files are related to netplan, so only remove those in netplan-related directories!
    – JanC
    May 5 '18 at 19:33

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