First, make a backup of the cluster:
cp -a /etc/pve /root/pve_backup
Stop cluster service:
/etc/init.d/pve-cluster stop
Umount /etc/pve if it is mounted:
umount /etc/pve
Stop corosync service:
/etc/init.d/cman stop
Remove cluster configuration:
# rm /etc/cluster/cluster.conf # rm -rf /var/lib/pve-cluster/*
Start again cluster service:
/etc/init.d/pve-cluster start
Now, you can create new cluster:
# pvecm create newcluster
Restore cluster and virtual machines configuration from the backup:
# cp /root/pve_backup/*.cfg /etc/pve/ # cp /root/pve_backup/qemu-server/*.conf /etc/pve/qemu-server/ # cp /root/pve_backup/openvz/* /etc/pve/openvz/
UPDATE: This post is also valid to change the hostname of a node in a cluster or to move a node between two clusters. When you have removed a node from the cluster, it still appears in the proxmox nodes tree, to remove it from the tree you have to delete the node directory from another node in the cluster:
# rm -rf /etc/pve/nodes/HOSTNAME