Test an insecure registryEstimated reading time: 3 minutes
While it’s highly recommended to secure your registry using a TLS certificate issued by a known CA, you may alternatively decide to use self-signed certificates, or even use your registry over plain http.
You have to understand the downsides in doing so, and the extra burden in configuration.
Deploying a plain HTTP registry
Warning: it’s not possible to use an insecure registry with basic authentication.
This basically tells Docker to entirely disregard security for your registry. While this is relatively easy to configure the daemon in this way, it is very insecure. It does expose your registry to trivial MITM. Only use this solution for isolated testing or in a tightly controlled, air-gapped environment.
Depending on your operating system, your Engine daemon start options.
Edit (or add) the
DOCKER_OPTSline and add the
This flag takes the URL of your registry, for example.
Close and save the configuration file.
Restart your Docker daemon
The command you use to restart the daemon depends on your operating system. For example, on Ubuntu, this is usually the
service docker stopand
service docker startcommand.
Repeat this configuration on every Engine host that wants to access your registry.
Using self-signed certificates
Warning: using this along with basic authentication requires to also trust the certificate into the OS cert store for some versions of docker (see below)
This is more secure than the insecure registry solution. You must configure every docker daemon that wants to access your registry
Generate your own certificate:
mkdir -p certs && openssl req \ -newkey rsa:4096 -nodes -sha256 -keyout certs/domain.key \ -x509 -days 365 -out certs/domain.crt
Be sure to use the name
myregistrydomain.comas a CN.
Use the result to start your registry with TLS enabled
Instruct every docker daemon to trust that certificate.
This is done by copying the
Don’t forget to restart the Engine daemon.
Troubleshooting insecure registry
This sections lists some common failures and how to recover from them.
Failing to configure the Engine daemon and trying to pull from a registry that is not using TLS will results in the following message:
FATA Error response from daemon: v1 ping attempt failed with error: Get https://myregistrydomain.com:5000/v1/_ping: tls: oversized record received with length 20527. If this private registry supports only HTTP or HTTPS with an unknown CA certificate,please add `--insecure-registry myregistrydomain.com:5000` to the daemon's arguments. In the case of HTTPS, if you have access to the registry's CA certificate, no need for the flag; simply place the CA certificate at /etc/docker/certs.d/myregistrydomain.com:5000/ca.crt
Docker still complains about the certificate when using authentication?
When using authentication, some versions of docker also require you to trust the certificate at the OS level. Usually, on Ubuntu this is done with:
$ cp certs/domain.crt /usr/local/share/ca-certificates/myregistrydomain.com.crt update-ca-certificates
… and on Red Hat (and its derivatives) with:
cp certs/domain.crt /etc/pki/ca-trust/source/anchors/myregistrydomain.com.crt update-ca-trust
… On some distributions, e.g. Oracle Linux 6, the Shared System Certificates feature needs to be manually enabled:
$ update-ca-trust enable
Now restart docker (
service docker stop && service docker start, or any other way you use to restart docker).