Temporary failure resolving (DNS errors during updates)

What this is#

Running apt update (or curl, git, anything that needs a hostname) fails with "Temporary failure resolving 'archive.ubuntu.com'" or "Could not resolve host". Your VPS's network is fine, but its DNS resolver isn't answering, so it can't turn names into IPs.

The fix#

Point systemd-resolved at a public resolver:

1. Edit the resolver config: nano /etc/systemd/resolved.conf
2. Find the #DNS= line, uncomment it, and set a resolver: DNS=8.8.8.8
3. Save (Ctrl+X, then Y) and restart the resolver: systemctl restart systemd-resolved

Or as a single command:

sed -i 's/#DNS=/DNS=8.8.8.8/' /etc/systemd/resolved.conf && systemctl restart systemd-resolved

Then retry the update. 8.8.8.8 is Google's public resolver; 1.1.1.1 (Cloudflare) works just as well.

If that doesn't do it#

• Check /etc/resolv.conf exists and isn't empty. On systemd-resolved systems it should be a symlink managed for you; on others, a plain nameserver 8.8.8.8 line in it does the job.
• Check your own firewall isn't blocking outbound DNS (UDP/TCP port 53), an overzealous ruleset with a default-deny on output does exactly this.
• Still stuck? Open a ticket with the exact error and what you've tried.

Related questions#

• "Why does apt update say temporary failure resolving?"
• "My VPS can't resolve any hostnames."
• "How do I fix DNS inside my VPS?"
• "Could not resolve host errors on my VPS."