Docker builds fail on Hetzner VPS due to DNS resolution (Nixpacks, Railpack, Dockerfile)

[tsolak9]

To Reproduce

1. Install Dokploy on a Hetzner Cloud VPS (fresh Ubuntu image)
2. Create an application from a GitHub repo (any Node.js project)
3. Deploy using any build type (Nixpacks, Railpack, or Dockerfile)
4. Build fails with DNS resolution errors

Nixpacks error: "Could not resolve host: github.com"
Railpack error: "lookup ghcr.io on 185.12.64.1:53: server misbehaving"
Dockerfile (npm ci): "Exit handler never called!" after ~141 seconds

Root cause: Hetzner's default DNS servers (185.12.64.1, 185.12.64.2) fail recursive resolution inside Docker build containers. Dokploy's install script does not configure Docker DNS.

Current vs. Expected behavior

Current: All build types fail with DNS errors on Hetzner VPS because Docker inherits Hetzner's broken DNS servers.

Expected: Builds should work out of the box, or the troubleshooting docs should mention this for Hetzner users.

Provide environment information

Operating System:
    OS: Ubuntu (latest Hetzner default image)
    Arch: x86_64
  Dokploy version: latest
  VPS Provider: Hetzner Cloud
  Application: Astro SSR (Node.js)

Which area(s) are affected? (Select all that apply)

Docker

Are you deploying the applications where Dokploy is installed or on a remote server?

Remote server

Additional context

Fix: Configure Docker to use public DNS resolvers:

sudo mkdir -p /etc/docker
echo '{"dns": ["1.1.1.1", "8.8.8.8"]}' | sudo tee /etc/docker/daemon.json
sudo systemctl restart docker

All three build types (Nixpacks, Railpack, Dockerfile) failed before this fix and worked immediately after. The issue is that Hetzner's DNS servers (185.12.64.1) don't support recursive resolution properly inside Docker containers.

Will you send a PR to fix it?

No

[Siumauricio]

This looks like a connectivity issue specific to your environment rather than a Dokploy bug. We've seen similar reports before, but they tend to be isolated to particular VPS configurations not consistent across all Hetzner servers in general.

The fact that all three build types (Nixpacks, Railpack, Dockerfile) fail with DNS errors points to a network/connectivity problem at the infrastructure level, not something Dokploy can control. The fix you found (pointing Docker to public DNS resolvers) confirms this.

If you're able to reproduce this on a fresh Hetzner server consistently, that would be useful information — but based on what we've seen, this doesn't seem to affect Hetzner users broadly.

[Siumauricio]

@dosubot review

[dosubot]

Thanks for the detailed issue report! This is a confirmed known issue that affects various VPS providers.

Your diagnosis and fix are correct. Other users experiencing the same "Could not resolve host: github.com" errors during builds have resolved it by configuring DNS in /etc/docker/daemon.json.

A few additional notes:

• Hetzner users have also reported related IPv6 networking issues — if DNS config alone doesn't help, ensuring IPv4 is properly configured may be worth trying
• This affects providers with aggressive DNS caching or network restrictions, not just Hetzner

Your suggestion to add this to the troubleshooting docs is valid — this scenario isn't currently documented. The fix you provided is the standard solution:

sudo mkdir -p /etc/docker
echo '{"dns": ["1.1.1.1", "8.8.8.8"]}' | sudo tee /etc/docker/daemon.json
sudo systemctl restart docker

To reply, just mention @dosu.

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