AIO mastercontainer exits with curl: (6) Could not resolve host: ghcr.io, while the same image can reach ghcr.io successfully

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I have spent several weeks debugging this and intentionally excluded the common causes (DNS, firewall, Pi-hole, VPN, Docker DNS, bridge networking).

Are you using the latest AIO image?

Yes.

Image:

ghcr.io/nextcloud-releases/all-in-one:latest

Created:

2026-06-26T08:34:24Z

Digest:

sha256:e7abd7c7f4f28ec63971e92fdcb03d361a85cd3e7d83cd50d19c375cad623614

Host system

Hardware:

  • Raspberry Pi 4 (8 GB)

OS:

  • Debian GNU/Linux 13 (Trixie)

Kernel:

  • 6.18.34+rpt-rpi-v8

Docker:

  • Docker Engine Community 29.6.1
  • Compose v5.3.0

Storage:

  • overlayfs
  • Docker Root Dir: /var/lib/docker

Problem

The AIO mastercontainer immediately exits with

curl: (6) Could not resolve host: ghcr.io

Could not reach https://ghcr.io.

Most likely is something blocking access to it.

The strange part

Everything else can resolve and reach ghcr.io.

Host:

ping ghcr.io

works.

Host:

curl -I https://ghcr.io

works.

Container:

docker run --rm alpine nslookup ghcr.io

works.

Container:

docker run --rm alpine sh -c "apk add --no-cache curl >/dev/null && curl -I https://ghcr.io"

works.

Even the SAME AIO image works:

docker run --rm 
--entrypoint /bin/bash 
ghcr.io/nextcloud-releases/all-in-one:latest 
-c "curl -I https://ghcr.io/v2/"

returns HTTP/2 405 successfully.

So the image itself clearly has working DNS/network access.

Docker DNS

daemon.json

{
  "dns": [
    "8.8.8.8",
    "1.1.1.1"
  ]
}

Host resolv.conf

nameserver 8.8.8.8
nameserver 1.1.1.1

Docker network

bridge network exists normally.

iptables looks normal.

No custom firewall.

No Pi-hole.

No proxy.

No VPN inside Docker.

Tailscale was stopped during testing.

Container

Entrypoint:

/start.sh

CMD:

null

NetworkMode:

bridge

What looks inconsistent

Inside /start.sh the following check exists:

if ! curl --no-progress-meter https://ghcr.io/v2/ >/dev/null; then

This curl reports

curl: (6) Could not resolve host: ghcr.io

However running exactly the same curl manually from the same image succeeds.

So it appears the startup environment behaves differently from a normal shell started from the image.

Question

Is this a known issue with

  • Docker Engine 29.6.x
  • Debian 13 (Trixie)
  • Raspberry Pi arm64

or is there another reason why curl inside /start.sh cannot resolve ghcr.io while the exact same image can?