LXC & Docker Containerization

Automating LXC Container Provisioning on Proxmox with Cloud-Init and Custom Cloud Images

**Problem**: The ops lead from a customer’s staging farm who had just recently configured a brand new Proxmox cluster contacted me with a request for thirty similar Ubuntu-based containers to be made available by lunchtime. Going through the GUI of Proxmox and configuring each container by manually entering information such as hostnames, usernames and SSH keys would not only take half the day but if there was any typo in any of the hostnames would require tearing down the container you created, starting again.

**Constraints**: I had no choice except to create light weight LXC containers since we would use all the system RAM. Furthermore, the customer wanted Ubuntu 24.04 LTS with zero configuration drift. The overhead of using full VMs was not necessary since we could not compromise on either of the two items above, therefore we created multiple identical containers with exactly the same secure and hardened SSH configuration, the same monitoring agent, and a single known set of users, without performing any manual steps after creation.

**Solution**: I built a custom LXC Template using the official Ubuntu Cloud Image and integrated the Provisioning using Proxmox’s Snippet Based User Data Cloud Init facility, causing me to be able to provision my entire request within approximately four minutes. That first deployment was a seamless installation, I felt like I was cheating because since that time I have never manually provisioned any container again.