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Configuring DNS resolution with systemd-resolved

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Configuring DNS resolution with systemd-resolved

systemd-resolved is a systemd service that resolves DNS queries asynchronously and in parallel, with its own cache — it can be used alongside, or instead of, traditional resolution via /etc/hosts and a static /etc/resolv.conf.

Prerequisites

  • A systemd-based Linux distribution.
  • Root/sudo access.

Steps

1. Configure resolved

Edit /etc/systemd/resolved.conf, in the [Resolve] section:

[Resolve]
DNS=<dns-server-ip>
Domains=<search-domain>

2. Enable and start the service

systemctl start systemd-resolved
systemctl enable systemd-resolved
systemctl status systemd-resolved

3. Point /etc/resolv.conf at resolved

Configuration alone isn’t enough — resolution still needs to actually be routed through resolved:

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

Verify

nslookup <some-domain>

Expect a response via the local stub resolver (127.0.0.53#53). Check live statistics:

resolvectl statistics
watch -n 1 resolvectl statistics

Troubleshooting

  • DNS still resolves the “old” way after configuring resolved.conf: the symlink step (step 3) is required — editing resolved.conf alone does not repoint /etc/resolv.conf.

  • Running inside a Proxmox LXC container and /etc/resolv.conf keeps reverting: Proxmox overwrites /etc/resolv.conf on container start by default. Create an empty marker file to stop it:

    touch /etc/.pve-ignore.resolv.conf

    After that, the steps above apply normally inside the container.

  • Need to change the DNS server later: it must be changed in /etc/systemd/resolved.conf itself (and the service restarted), not via /etc/resolv.conf, since that file is now just a symlink to the resolved stub.

Alternative: static resolv.conf

systemd-resolved isn’t the only way to pin a DNS server on Ubuntu/Debian. A simpler, more “static” alternative: delete the /etc/resolv.conf symlink entirely and replace it with a plain, non-symlinked file that nothing manages or regenerates automatically.

sudo rm /etc/resolv.conf
echo "nameserver <dns-server-ip>
options edns0 trust-ad
search <search-domain>" | sudo tee /etc/resolv.conf > /dev/null
sudo chmod 644 /etc/resolv.conf

Verify with:

cat /etc/resolv.conf

Trade-offs versus systemd-resolved:

  • No local caching or asynchronous/parallel resolution — every lookup goes straight to the configured server(s).
  • It permanently overrides whatever DHCP or other network management would otherwise set — useful when that’s exactly the point (a server that must never silently pick up a different resolver), but it means the file has to be revisited manually if the network’s DNS setup changes, and anything that expects to manage /etc/resolv.conf (NetworkManager, systemd-resolved itself, DHCP client hooks) will either fight with it or silently have no effect.
  • No resolvectl-style per-interface visibility or statistics — just the one flat file.

Use this when a host needs a DNS setting that absolutely will not change without a manual edit (e.g. deliberately bypassing DHCP-provided DNS); use systemd-resolved (above) for the caching, async resolution and per-interface flexibility instead.

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