Do I need to list registry-mirrors in no-proxy when writing daemon.json ?

[ianzone]

Need direct connections to the registry-mirrors when pulling images while using the proxy to login.

[christianalberto]

Yes, absolutely. If your registry mirror is located within your local/internal network (or accessible directly without going through the outbound proxy), you must list its domain or IP address in the no-proxy list inside daemon.json (or your environment settings).

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Why this happens

When a proxy is configured for the Docker daemon:

1. Docker routes all outgoing HTTP/HTTPS traffic (including image pulls) through the proxy by default.
2. If your registry-mirrors host is not specified in no-proxy, Docker will attempt to reach the local/internal mirror via the proxy.
3. This usually results in connection timeouts, 502/504 proxy errors, or routing loops if the proxy cannot reach internal infrastructure.

---

How to configure it in daemon.json

Add your mirror's host domain or IP (and optionally its port) to no-proxy (or NO_PROXY in environment configuration):

{
  "registry-mirrors": [
    "[https://mirror.internal.company.com:5000](https://mirror.internal.company.com:5000)"
  ],
  "proxies": {
    "http-proxy": "[http://proxy.company.com:8080](http://proxy.company.com:8080)",
    "https-proxy": "[http://proxy.company.com:8080](http://proxy.company.com:8080)",
    "no-proxy": "localhost,127.0.0.1,mirror.internal.company.com,.company.com"
  }
}

Note: Remember to reload and restart the Docker daemon after saving changes:

Bash
sudo systemctl reload docker # or sudo systemctl restart docker
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