Clusters change: hardware is retired, and small clusters need help to keep quorum. This guide shows how to remove a node from a Proxmox cluster cleanly and how a QDevice gives a two-node cluster the third vote it needs.
Before you start
- Root shell on the cluster nodes.
- All VMs and containers moved off the node you will remove (migrate VMs), and its HA resources and replication jobs deleted.
- For a QDevice: a small separate Linux machine or VM outside the cluster (a Raspberry Pi or small VPS works).
Remove a node from the Proxmox cluster
- Check the cluster:
pvecm statusandpvecm nodes. - Power off the node being removed. It must not come back online with the same configuration.
- On a remaining node, remove it:
pvecm delnode pve3- Remove the leftover directory so it disappears from the web UI:
rm -r /etc/pve/nodes/pve3(check the name carefully). - Remove the old node's entries from SSH known hosts if you will reuse its name or IP.
Warning: Never start the removed node on the same network without reinstalling it. It still believes it is in the cluster and can disturb corosync.
Why a QDevice
A two-node cluster has two votes. If one node fails, the survivor has 50% and loses quorum, so it cannot start or change VMs. A QDevice adds a third vote from an outside machine, so the surviving node keeps quorum.
Add a QDevice
- On the external machine (Debian/Ubuntu):
apt install corosync-qnetd. - On every cluster node:
apt install corosync-qdevice. - Make sure root SSH from one cluster node to the QDevice machine works (password or key).
- On one cluster node, run:
pvecm qdevice setup 192.0.2.50- Check with
pvecm status: you should see the QDevice listed and 3 expected votes.
Troubleshooting
- Removed node still visible: delete its directory under
/etc/pve/nodes. - QDevice setup fails: SSH as root to the QDevice host is blocked, or the packages are missing on a node.
- Quorum lost during removal: too many nodes offline at once; bring nodes back before continuing.
Frequently asked questions
Do I need a QDevice with three nodes?
Not normally. With an even number of nodes, a QDevice can help, but it is mainly for two-node clusters.
Can the QDevice be far away?
Yes, it only needs a stable connection; latency is less critical than for corosync between nodes.
Can I re-add a removed node?
Reinstall Proxmox on it first, then join it as a new node.