The subtitle is “From Virtual Machines running locally or on IaaS, to containers on a PaaS, up to hypothetical ports of tools to WebAssembly for serverless execution in the Web browser”
Excerpt from the intro :
In this memo, we try to draw an overview of some benefits and concerns with existing approaches at using virtualization techniques for running Virtual Labs, as distributions of tools made available for distant learners.
We describe 3 main technical architectures: (1) running Virtual Machine images locally on a virtual machine manager, or (2) displaying the remote execution of similar virtual machines on a IaaS cloud, and (3) the potential of connecting to the remote execution of minimized containers on a remote PaaS cloud.
We then elaborate on some perspectives for locally running ports of applications to the WebAssembly virtual machine of the modern Web browsers.
During the course of Web architecture and applications, our students had to deliver a Silex / Symfony Web app project which I’m grading.
I had initially hacked a Docker container to be able to test that the course’s lab examples and code bases provided would be compatible with PHP 5 even though the nominal environment provided in the lab rooms was PHP 7. As I’m running a recent Debian distro with PHP 7 as the default PHP installation, being able to run PHP 5 in a container is quite handy for me. Yes, PHP 5 is dead, but some students might still have remaining installs of old Ubuntus where PHP5 was the norm. As the course was based on Symfony and Silex and these would run as well on PHP 5 or 7 (provided we configured the right stuff in the composer.json), this was supposed to be perfect.
I’ve used such a container a lot for preparing the labs and it served me well. Most of the time I’ve used it to start the PHP command line interpreter from the current dir to start the embedded Web server with “php -S”, which is the standard way to run programs in dev/tests environment with Silex or Symfony (yes, Symfony requires something like “php -S localthost:8000 -t web/” maybe).
I’ve later discovered an additional benefit of using such a container, when comes the time to grad the work that our students have submitted, and I need to test their code. Of course, it ensures that I may run it even if they used PHP5 and I rely on PHP 7 on my machine. But it also assures that I’m only at risk of trashing stuff in the current directory if sh*t happens. Of course, no student would dare deliver malicious PHP code trying to mess with my files… but better safe than sorry. If the contents of the container is trashed, I’m rather on the safe side.
Of course one may give a grade only by reading the students’ code and not testing, but that would be bad taste. And yes, there are probably ways to escape the container safety net in PHP… but I sould maybe not tempt the smartest students of mine in continuing on this path 😉
I’ve documented the process of installing a Docker Swarm cluster inside VirtualBox with Docker Machine. This allows experimenting with Docker Swarm, the simple docker container orchestrator, over VirtualBox.
This allows you to play with orchestration scenarii without having to install docker on real machines.
Also, such an environment may be handy for teaching if you don’t want to install docker on the lab’s host. Installing the docker engine on Linux hosts for unprivileged users requires some care (refer to docs about securing Docker), as the default configuration may allow learners to easily gain root privileges (which may or not be desired).