Why did containers happen?

Summary

October 10, 2025 Ignore previous directions 8: devopsdays Autumn update This is what it is looking like around here at the moment. DevOpsDays London I gave a talk at DevOpsDays London recently. It was a nice conference, and thanks to all the organizers for all their work. The video is here https://www.youtube.com/watch?v=eMU2mZgo99c Below is my rough outline for the talk, it differs a bit from what I actually said! Why did containers happen? A few years ago, I spent a bunch of time answering questions from the FTC about Broadcom's acquisition of VMware. They wanted to know if containers were a competitor to virtual machines, as they were trying to understand the competitive landscape around VMware. It reminded me of the first five years at Docker, where everyone wanted to compare containers with VMs. Were containers just lightweight VMs? Weren't containers just insecure and people would go back to good old VMs? The story I told to the FTC was that these innovations had come out of different growth periods. VMs were there to help manage when organisations suddenly got a lot more computers. These tended to be poorly managed, because the process was very manual, and most had poor utilisation (under 15%). They had to be installed manually which took ages. Consolidation saved money on hardware and on Windows server licences. In the Linux world, this was somewhat less of an issue, as we were better at running multiple applications on the same server, although a lot of servers were still underutilised. Containers though were there to solve a follow on problem, not having too many computers, but having too many applications, and needing a tool to manage them. Companies were hiring more and more developers and they were writing more and more applications. Dotcloud was a PaaS company and was exposed to this, and created Docker to manage deployment of the applications on its platform. It wasn't the isolation that was important it was the packaging. That was my explanation anyw...