How to reset cluster configuration in Proxmox

If you have already made the proxmox cluster, but you want to make changes to the cluster config, for example for changing the hostname of the node, or the network with which the nodes are communicating on in the cluster, you can remove the cluster and create it again:

>> 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

Sumber : http://undefinederror.org/how-to-reset-cluster-configuration-in-proxmox-2/