17

I would like to use DHCP to assign an IP address to my server, but specify the DNS servers manually. I tried the following simple configuration:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      dhcp4: yes
      nameservers: [8.8.8.8,8.8.4.4]

After running netplan apply I check the nameservers with systemd-resolve --status and it shows:

DNS Servers: 8.8.8.8
             8.8.4.4
             192.168.1.1

The last is the DNS server provided by DHCP, which I do not want to be in the list.

Does netplan have a way to accomplish this?

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4
  • You may find the answer here helpful unix.stackexchange.com/questions/136117/…
    – nucc1
    May 5, 2018 at 12:35
  • I appreciate the attempt to help, but dhclient.conf does not appear to affect netplan configured DHCP at all. In fact, on Ubuntu 17.10 I found that you could delete the dhclient binary and netplan would still configure everything with DHCP.
    – alanwj
    May 7, 2018 at 7:18
  • I found the bug (you?) filed on netplan for this: bugs.launchpad.net/netplan/+bug/1759014 I skimmed the netplan code and it doesn't support any way to specify DHCP options. It is hardcoded to write two options "UseMTU" and "RouteMetric". The only way I can think of for "hacking" what you want is to manually (or using a script) edit the files in /run/systemd/network/10-netplan-* which is where networkd reads definitions from. YOu can append the dhcp options you want there . doesn't look too complex to support this, so maybe we will see a patch in our lifetimes.
    – nucc1
    May 7, 2018 at 11:36
  • of course, as you know, the files will be overwritten every time you call netplan apply... also, my comments are based on Ubuntu 18.04 and the current Master of netplan.
    – nucc1
    May 7, 2018 at 11:45

4 Answers 4

Reset to default
14

This has been fixed in the netplan repository on github, and will presumably make its way into Ubuntu at some point.

Two new options have been added, dhcp4-overrides and dhcp6-overrides. To ignore DNS servers from DHCP you would do something like:

dhcp4: yes
dhcp4-overrides:
  use-dns: no
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2
  • 3
    I agree this is the best fix. However, if you don't have the latest netplan (for example, you're on 18.04 like me), you can instead append "UseDNS=false" to /run/systemd/network/10-netplan-*.network, then execute systemctl restart systemd-networkd. Note that a future netplan apply will clobber this. (Info from bugs.launchpad.net/netplan/+bug/1759014/comments/5)
    – Chris
    Jan 22, 2019 at 15:19
  • Works on 18.04, netplan/bionic 1.10.1-5build1
    – Gaia
    Jun 2, 2020 at 22:28
5

There is unfortunately no changelog in the netplan github repo to ascertain when the newer features came in. However there was a big jump in release versions in https://github.com/CanonicalLtd/netplan/releases from 0.40 to 0.90 in November 2018

On Ubuntu 18.10, netplan is presently at version 0.40.2.2

With that netplan version, trying a wireless config to do DHCP but with the Cloudflare anonymous DNS servers:

network:
  version: 2
  renderer: NetworkManager
    ethernets:
      wlp4s0:
        dhcp4: yes
        dhcp4-overrides:
          use-dns: no
        nameservers:
          addresses: [1.1.1.1,1.0.0.1]

produces an Unknown key dhcp4-overrides error:

enter image description here

There are no backports to cosmic according to ubuntu.packages.org

On Ubuntu 19.04 beta, netplan version 0.96 is installed and the dhcp4-overrides can be used:

enter image description here

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2
  • This is working on ubuntu 18.04 right now (netplan 0.98)
    – Giovanni Toraldo
    Mar 9, 2020 at 8:34
  • Cool. I see that 19.10 uses netplan 1.10.1 so issue should be resolved there too
    – timbo
    Mar 9, 2020 at 20:12
2

This is a really common setup that's totally borked in Ubuntu 18.04, Netplan needs to support the NetworkManager options when using DHCP:

nmcli connection modify ${ID} ipv4.ignore-auto-dns yes
nmcli connection modify ${ID} ipv4.dns 'xx.xx.xx.10 xx.xx.xx.20'
nmcli connection modify ${ID} ipv4.dns-search 'abc01.domain.com. abc02.domain.com.'
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1

Using dhcp6-overrides with 'use-dns: false' doesn't work to ignore DNS servers provided over DHCP6.

NB: I'm using netplan.io 0.96 and systemd 240 in Ubuntu 19.04 (disco).

# cat /etc/netplan/10-enp3s0-init.yaml
network:
    version: 2
    renderer: networkd
    ethernets:
        enp3s0:
            critical: true
            dhcp4: true
            dhcp4-overrides:
                use-dns: false
            dhcp6: true
            dhcp6-overrides:
                use-dns: false
            ipv6-privacy: true
            nameservers:
                search: [home]
                addresses: [1.0.0.1, 1.1.1.1]

# resolvectl status enp3s0
Link 2 (enp3s0)
      Current Scopes: DNS
DefaultRoute setting: yes
       LLMNR setting: yes
MulticastDNS setting: no
  DNSOverTLS setting: opportunistic
      DNSSEC setting: yes
    DNSSEC supported: yes
  Current DNS Server: 1.0.0.1
         DNS Servers: 1.0.0.1
                      1.1.1.1
                      fd50:a94:67b3:0:26a7:dcff:fe27:a60 <--- DHCP6 provided?
          DNS Domain: home
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1
  • 1
    I fixed this by uninstalling netplan and just using /etc/systemd/network/*.network files to configure networking accordingly.
    – trcm
    May 6, 2019 at 9:44

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