Oh, perhaps I misunderstood your question. If you mean why can't I completely replace them with newly built containers, it's because they are complete but rath

Oh, perhaps I misunderstood your question. If you mean why can't I completely replace them with newly built containers, it's because they are complete but rather old OS images with years of configuration history in them, running specific versions of mission critical applications. They are older than LXC, and were originally run on real servers, then under chroot and UML, then under KVM, before LXC or Docker were a thing. To be tinkered with most carefully. As much as I would like to restart from scratch, with new versions of everything, experience has taught me it would be unwise to do it in a hurry, or without extensive testing. So yes they can be replaced and will be eventually, but it's not a small job and will need time scheduled to it. For the time being it's the Right Thing To Do(tm) to keep the existing images still running as they are.