Information
You should verify that the Docker server certificate key file (the file that is passed along with the --tlskey parameter) has permissions of 400.
Rationale:
The Docker server certificate key file should be protected from any tampering or unneeded reads. It holds the private key for the Docker server certificate. It must therefore have permissions of 400 to ensure that the certificate key file is not modified.
Impact:
None.
Solution
You should execute the following command:
chmod 400 <path to Docker server certificate key file>
This sets the Docker server certificate key file permissions to 400.
Default Value:
By default, the permissions for the Docker server certificate key file might not be 400. The default file permissions are governed by the operating system or user specific umask values.