问题:

Read some PPTs, it seems that one container can run on different linux vendors. Is is true?

回答1:

Yes. That's the main idea of docker.

It creates a "static container" in a chrooted env that is able to run on any linux because all the needed user-land dependencies are included in the image.

Since linux (the kernel) maintains a backward compatibility on system calls and their call-schemes, the idea can work across versions and even different distributions of Linux.

Of course, the binary architecture (say amd64) needs to be the same on the source and target system.

回答2:

Yes, for most applications this works. The kernel is whatever you are really running on (RedHat in your example) while the userspace is supplied by the container (Ubuntu).

Most Linux kernel variants are sufficiently similar that applications will not notice. However if the code relies on something specific in the kernel that is not there, Docker can't help you.

Docker itself relies on certain minimum kernel features, version 3.8 at the time of writing. https://docs.docker.com/engine/installation/binaries/