I have been working on private organization and there is restricted policy for downloading docker images. So I am planning to use default RHEL server to convert tar.gz and try to import on docker engine.
If anyone has the details please share for changing normal server to docker image.
Deploy your own local Docker registry to allow pull from hosts without Internet.
Consider still basing your images on Docker Hub images or similar examples. A container environment is different from a full operating system with a kernel. Push images from a host with Internet.
Documentation suggests crossing an air-gap is possible. The usual consideration that you need a way to copy or migrate storage without an IP network applies.