Information
https://docs.docker.com/articles/certificates/
2.http://docs.docker.com/articles/https/
Solution
chmod 400 <path to Docker server certificate key file>This would set the Docker server certificate key file permissions to '400'.
Impact-
None.
Default Value-
By default, the permissions for Docker server certificate key file might not be '400'. The default file permissions are governed by the system or user specific umask values.