That only works for the Docker backends that are based on Linux namespaces. What about backends like OpenVZ or FreeBSD jails? Even if I limit the scope to Linux

That only works for the Docker backends that are based on Linux namespaces. What about backends like OpenVZ or FreeBSD jails? Even if I limit the scope to Linux namespaces, for arbitrary shell commands to work properly, I have to know exactly which namespaces Docker use, which may be version-specific or configuration-specific.