an invention by cyphar
In many cases, people want to start containers on a system where the administrator is not happy about granting privileges to users or installing any new software. For example, when I was a researcher and wanted to run Python 3 on a computing cluster it was not possible to get the administrator to install Docker or Python 3. In recent Linux kernels, it has been possible to create containers without any privileges. All that's missing is a container runtime that allows you to do this. LXC is close but falls short (it requires certain privileged processes and PAM modules for everything to work).