Debian 10/9/8 DNS configuration bug

[ubuntu-server-builder]

This bug was originally filed in Launchpad as LP: #1850310

Launchpad details

affected_projects = []
assignee = None
assignee_name = None
date_closed = None
date_created = 2019-10-29T12:45:21.422366+00:00
date_fix_committed = None
date_fix_released = None
id = 1850310
importance = medium
is_complete = False
lp_url = https://bugs.launchpad.net/cloud-init/+bug/1850310
milestone = None
owner = dshemin
owner_name = Dmitry Shemin
private = False
status = triaged
submitter = dshemin
submitter_name = Dmitry Shemin
tags = []
duplicates = []

Launchpad user Dmitry Shemin(dshemin) wrote on 2019-10-29T12:45:21.422366+00:00

I use cloud-init with NoCloud data source for configuring my VM's and got strange bug with DNS configuration on official Debian images like https://cdimage.debian.org/cdimage/openstack/current-10/debian-10-openstack-amd64.qcow2.

My network config:

version: 2
ethernets:
  eth0:
    set-name: eth0
    match:
      macaddress: <MAC address>
    addresses: [ <IP address> ]
    gateway4: <GATEWAY ADDRESS>
    nameservers:
      addresses: [8.8.8.8,8.8.4.4]

After creating new VM I got next configuration in /etc/network/interfaces.d/50-cloud-init.cfg which is seems ok:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
    address 10.52.240.11/16
    dns-nameservers 8.8.8.8 8.8.4.4
    gateway 10.52.1.1

But /etc/resolv.conf contains:

nameserver 127.0.0.1

Which leads to the fact that I can’t resolve any domain name, for example:

# ping google.com
ping: google.com: Temporary failure in name resolution

[ubuntu-server-builder]

Launchpad user Dmitry Shemin(dshemin) wrote on 2019-10-29T12:45:21.422366+00:00

Launchpad attachments: cloud-init.tar.gz

[ubuntu-server-builder]

Launchpad user Ryan Harper(raharper) wrote on 2019-10-30T15:34:35.067799+00:00

Thanks for filing the bug.

Cloud-init itself does not render /etc/resolv.conf on Ubuntu/Debian; In Ubuntu, the resolvconf package is installed which handles maintain /etc/resolv.conf.

Looking at:

https://cdimage.debian.org/cdimage/openstack/current-10/debian-10-openstack-amd64-packages.list

resolvconf package is not present, hence the bug. I would suggest that the images include this package.

That said, cloud-init could detect if resolvconf is not present and render resolv.conf directly.

[ubuntu-server-builder]

Launchpad user Adam Conrad(adconrad) wrote on 2019-10-30T15:53:08.950232+00:00

In Ubuntu, the resolvconf package is installed which handles maintain /etc/resolv.conf.

This hasn't been true for years. That said, it's still handled "magically" today, just that now we do it with systemd-resolved.

[ubuntu-server-builder]

Launchpad user Ryan Harper(raharper) wrote on 2019-10-30T16:08:06.595966+00:00

@adam,

In the context of Ubuntu images which still use ifupdown by default (Xenial); they also include resolvconf which is what manages resolv.conf.

As you note, newer Ubuntu uses systemd-resolved as replacement for resolvconf; cloud-init on Ubuntu does not directly render contents into /etc/resolv.conf for these reasons.

[ubuntu-server-builder]

Launchpad user Dmitry Shemin(dshemin) wrote on 2019-10-30T18:03:52.568215+00:00

The documentation says that the 'resolvconf' package is optional for Debian. https://wiki.debian.org/NetworkConfiguration#Defining_the_.28DNS.29_Nameservers
So temporarily I used 'systemd-resolved' for DNS configuration by adding this line to my user data:

runcmd:
 - |
   cat << EOL > /etc/systemd/resolved.conf
   [Resolve]
   DNS=8.8.8.8
   EOL
 - |
   cat << EOL > /etc/resolv.conf
   nameserver 127.0.0.53
   EOL
 - systemctl enable systemd-resolved
 - systemctl start systemd-resolved

But I think it's worth doing something about it.

[ubuntu-server-builder]

Launchpad user Brian King(inflatador) wrote on 2020-05-29T17:17:00.830918+00:00

I'm affected as well. Running an Openstack cloud with the config-drive and static IP information. The DNS servers are in the network-data.json file, but cloud-init on Debian 10 does not set the DNS servers unless the resolvconf package is present.

[ubuntu-server-builder]

Launchpad user TJ(zimmertr) wrote on 2020-08-26T21:52:27.905610+00:00

I'm affected as well. Got around this like so:

write_files:

• path: /etc/resolvconf/resolv.conf.d/base
  content: nameserver 192.168.1.100
  runcmd:
• [ systemctl, restart, resolvconf ]