Proxmox

Proxmox Virtual Environment is a Debian-based virtualization platform combining KVM for full virtual machines, LXC for containers, and a clustering layer, behind one web interface and API.

The reason it matters is positioning rather than novelty. KVM and LXC are standard Linux technology available anywhere; Proxmox assembles them with clustering, storage integration, backup, and management into something a small team can run without either a commercial licence or building the stack themselves.

VMs and containers in one place

The dual model is more useful than it first appears. LXC containers share the host kernel — fast to start, low overhead, and appropriate for Linux workloads that do not need kernel isolation. KVM virtual machines are fully isolated with their own kernel, needed for other operating systems, kernel modules, or anything requiring a genuine security boundary.

Having both under one interface means the choice is per-workload rather than per-platform. A lightweight internal service runs as a container; anything needing isolation or a different kernel runs as a VM. Most platforms make you commit to one model.

Note that LXC containers are not Docker containers. LXC is system containers — a full userspace you administer like a machine — where Docker is application containers. Running Docker inside a Proxmox VM is the usual arrangement, and running it in an LXC container is possible and fiddly.

Clustering and shared storage

Multiple nodes form a cluster with a shared configuration and a single interface. The payoff is live migration — moving a running VM between hosts with no downtime — which makes host maintenance possible without scheduling an outage.

Live migration requires shared storage, and this is the architectural decision to get right early. Ceph is the standard choice and integrates directly; NFS or iSCSI also work. Local storage means migration requires copying the disk, which is slow and not live.

Ceph under Proxmox wants enough nodes to be sensible — three is the practical minimum and has little margin.

Practical notes

Backup is built in and works, including scheduled snapshots and restore. It is worth configuring on day one rather than after the first incident.

The subscription is for the enterprise repository and support; the software is open source and the no-subscription repository is fully functional. For institutional use a subscription buys tested updates, which is worth more than it costs when the platform holds production systems.

See also: Ceph, Docker Compose, Checkmk, and Linux administration in datacenters.