I've always wondered why only Linux can do 'true' containers without VMs. Is there a good blog post or something I can read about the various technical hurdles?
BSD can do BSD containers with Jails for more than a decade now?
Due to innate features of a container, it can be of the same OS of the host running on the system, since they have no kernel. Otherwise you need to go the VM route.
> Containers build on top of the host operating system's kernel (...), and contain only apps and some lightweight operating system APIs and services that run in user mode
> You can increase the security by using Hyper-V isolation mode to isolate each container in a lightweight VM
I'm not sure about MacOS, but otherwise all major OSs today can run containers natively. However, the interest in non-Linux containers is generally very very low. You can absolutely run Kubernetes as native Windows binaries [0] in native Windows containers, but why would you?
Note that containers, by definition, rely on the host OS kernel. So a Windows container can only run Windows binaries that interact with Windows syscalls. You can't run Linux binaries in a Windows container anymore than you can run them on Windows directly. You can run Word in a Windows container, but not GCC.
Is there any limitation in running older.NET Framework on current Windows? Back when I was using it, you could have multiple versions installed at the same time, I think.
Containers are essentially just a wrapper tool for a linux kernel feature called cgroups, with some added things such as layered fs and the distribution method.
You can also use just use cgroups with systemd.
Now, you could implement something fairly similar in each OS, but you wouldn't be able to use the vast majority of contained software, because it's ultimately linux software.