In Ubuntu 18.04 network configuration is managed by Netplan and it’s causing a lot of confusion and frustration for people who aren’t aware of the change.
Most people just want the short answer so here it is, you’ll need to know the IP address, gateway and nameservers.
The network config file in /etc/netplan should be named something like 50-cloud-init.yaml so open it up and configure your network like this.
Important: Tab indentation is forbidden in YAML files, you must use spaces instead.
network:
version: 2
renderer: networkd
ethernets:
eth0:
dhcp4: no
dhcp6: no
addresses: [192.168.1.70/24]
gateway4: 192.168.1.1
nameservers:
addresses: [192.168.1.1, 8.8.8.8, 8.8.4.4]
Once you’re done with editing the file run this command:
sudo netplan apply
You’re done, now check ifconfig and test the network.
If it doesn’t work then run this command:
sudo netplan --debug apply
This will give you hints about what might be wrong.
And here’s how to configure a static IP address and bridge for an LXD containers host.
Step 1. Finding the new configuration files in Ubuntu 18.04
Prior to 18.04 network configuration was done in /etc/network/interfaces but in Bionic Beaver the new config files are found in /etc/netplan:
[email protected]:~$ ls -lh /etc/netplan total 4.0K -rw-r--r-- 1 root root 388 Jan 5 22:15 01-netcfg.yaml
and here’s how it looks when properly configured for an LXD host:
# This file describes the network interfaces available on your system
# For more information, see netplan(5).
network:
version: 2
renderer: networkd
ethernets:
ens33:
dhcp4: no
dhcp6: no
bridges:
br0:
interfaces: [ens33]
dhcp4: no
addresses: [192.168.1.101/24]
gateway4: 192.168.1.1
nameservers:
addresses: [192.168.1.1]
As you can see my physical network is reported as ens33 and I’ve disabled all DHCP because I’m using static addressing for this machine, the br0 bridge settings are pretty straightforward and easy to understand.
After editing the config file you should apply the changes like this
[email protected]:/etc/netplan# netplan --debug apply ** (generate:1774): DEBUG: Processing input file //etc/netplan/01-netcfg.yaml.. ** (generate:1774): DEBUG: starting new processing pass ** (generate:1774): DEBUG: br0: setting default backend to 1 ** (generate:1774): DEBUG: ens33: setting default backend to 1 ** (generate:1774): DEBUG: Generating output files.. ** (generate:1774): DEBUG: NetworkManager: definition br0 is not for us (backend 1) ** (generate:1774): DEBUG: NetworkManager: definition ens33 is not for us (backend 1) DEBUG:netplan generated networkd configuration exists, restarting networkd DEBUG:no netplan generated NM configuration exists DEBUG:device ens33 operstate is up, not replugging DEBUG:netplan triggering .link rules for ens33 DEBUG:device br0 operstate is up, not replugging DEBUG:netplan triggering .link rules for br0 DEBUG:device lo operstate is unknown, not replugging DEBUG:netplan triggering .link rules for lo
Once you’re comfortable with the syntax you can omit the –debug switch and just use netplan apply but I recommend using the debug switch until then.
Check your configuration is working with
[email protected]:/etc/netplan# ifconfig -a br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.1.101 netmask 255.255.255.0 broadcast 192.168.1.255 inet6 fe80::64df:7dff:fe1c:8b03 prefixlen 64 scopeid 0x20 ether 69:dd:7d:1c:8d:01 txqueuelen 1000 (Ethernet) RX packets 12172 bytes 2051194 (2.0 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 504 bytes 55974 (55.9 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 ether 00:0d:29:c4:01:d3 txqueuelen 1000 (Ethernet) RX packets 2673456 bytes 1747246330 (1.7 GB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 501 bytes 57198 (57.1 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 46 bytes 3661 (3.6 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 46 bytes 3661 (3.6 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
and
[email protected]:/etc/netplan# networkctl status -a ● 1: lo Link File: /lib/systemd/network/99-default.link Network File: n/a Type: loopback State: carrier (unmanaged) Address: 127.0.0.1 ::1 ● 8: ens33 Link File: /lib/systemd/network/99-default.link Network File: /run/systemd/network/10-netplan-ens33.network Type: ether State: carrier (configured) Path: pci-0000:02:01.0 Driver: e1000 Vendor: Intel Corporation Model: 82545EM Gigabit Ethernet Controller (Copper) (PRO/1000 MT Single Port Adapter) HW Address: 00:0d:29:c4:0b:d4 ● 9: br0 Link File: /lib/systemd/network/99-default.link Network File: /run/systemd/network/10-netplan-br0.network Type: ether State: routable (configured) Driver: bridge HW Address: 61:df:71:1b:8b:02 Address: 192.168.1.101 fe80::64df:7dff:fe1c:8b03 Gateway: 192.168.1.1 (ARADOR CORPORATION) DNS: 192.168.1.1
And check your connectivity with pings and such.
WARNING: If you made changes to /etc/network/interfaces you must undo them or the above won’t work and you’ll have all kinds of weird stuff going on that makes no sense to you. I hope this helped and if you’re still having problems leave a comment below and I’ll try to help.
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How to make it work with LXD bridge?
I have similar config, but with lxdbrd0 and after netplan apply it works like a charm, but after reboot it for some reason sets broadcast as 0.0.0.0 for bridge. After another netplan apply it works again,,
The main issues I had getting this to work was with DHCP but once I ensured there was nothing in my /etc/network/interfaces and that the Netplan config had dhcp4:no and dhcp6:no for both network and bridge then the problems went away, although I do recall having to manually configure the routing on one of my boxes and reboot my router but I believe that was due to a /etc/network/interfaces conflict.
Thank you worked like a charm
Another useful command of netplan is try. This allows it to read the config file and, if there are errors, roll back to the previous config. Very cool if you are trying this remotely. Also adding the –debug to the try command gives details of the internals of how it is reading the config file and where it is tripping up.
netplan try and netplan –debug try
Helpful tips, thanks Jim.
I’m using Vi to edit the file, and when I add the “:” it changes the color of the text to blue and the “:” to red. What am I doing wrong? (I’m a newbee to the UNIX command line, but a DOS veteran.) I basically know how to open in Vi and to save my changes; that’s about all.
Thanks. This worked in my lab on a physical Ubuntu server machine.