Ubuntu 18.04 Netplan

Ubuntu 18.04 used a YAML based file with Netplan to configure the networking. I need to set up a server for virtualisation hosting with bonded uplinks to the ethernet switch.

This page build on the basic config to have a bonded ethernet with a vlan driver next to pick off vlans from the bond0 interface, and then the bridging driver on the vlans to allow a guest to connect to any vlan presented.

network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      dhcp4: yes

network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      addresses:
        - 192.168.5.YYY/24
      gateway4: 192.168.5.ZZZ
      nameservers:
          search: [rainsbrook.co.uk, sub.rainsbrook.co.uk]
          addresses: [192.168.5.XXX, 1.1.1.1]

This renames the “newer” style of naming ethernet to the more traditional eth0/1/2 etc based on the MAC address of the interface.

network:
  version: 2
  renderer: networkd

  ethernets:
    eth0:
      match:
        macaddress: 00:30:48:c0:ff:ee
      dhcp4: no
      dhcp6: no
      optional: true
      set-name: eth0

    eth1:
      match:
        macaddress: 00:fe:de:ad:be:ef
      dhcp4: no
      dhcp6: no
      optional: true
      set-name: eth1

  bonds:
    bond0:
      interfaces: [ eth0, eth1 ]
      dhcp4: no
      dhcp6: no
      parameters:
          mode: active-backup
          primary: eth0

  vlans:
    vlan5:
      accept-ra: no
      id: 5
      link: bond0
      dhcp4: no
      dhcp6: no

  vlans:
    vlan7:
      accept-ra: no
      id: 7
      link: bond0
      dhcp4: no
      dhcp6: no


  bridges:
    br1:
      addresses: [ 192.168.1.x/24 ]
      dhcp4: no
      dhcp6: no
      interfaces: [ bond0 ]
      gateway4: 192.168.1.1
      nameservers:
        addresses: [ 192.168.1.x ]
        search:    [ domain1.co.uk, domain1.int ]
    br5:
      dhcp4: no
      dhcp6: no
      interfaces: [ vlan5 ]

    br7:
      dhcp4: no
      dhcp6: no
      interfaces: [ vlan7 ]

/etc/resolv/conf is now a symlink as below:-

root@argon:~# ls -l /etc/resolv.conf
lrwxrwxrwx 1 root root 39 Apr  3 08:41 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf
 
root@argon:~# ls -l /run/systemd/resolve/*
-rw-r--r-- 1 systemd-resolve systemd-resolve 633 Apr  3 12:04 /run/systemd/resolve/resolv.conf
-rw-r--r-- 1 systemd-resolve systemd-resolve 760 Apr  3 12:04 /run/systemd/resolve/stub-resolv.conf

Two choices seem to exist, the resolv.conf file is the one updated by netplan, so let's use this:-

root@argon:~# ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
ln: failed to create symbolic link '/etc/resolv.conf': File exists
root@argon:~# mv /etc/resolv.conf /etc/resolv.conf.orig
root@argon:~# ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
root@argon:~# rm /etc/resolv.conf.orig

You could just use ln -sf to force the link creation, but if something goes wrong, you loose the original file.

Test with dig or nslookup and resolution should work as expected.