Proxmox VE 4.x

Upgrade 3.x versioonilt 4-le

# Upgrade to latest clean PVE version
apt-get update && apt-get dist-upgrade

# Remove node from cluster
pvecem delnode NODE_NAME

# Remove PVE
apt-get remove proxmox-ve-2.6.32 pve-manager corosync-pve openais-pve redhat-cluster-pve pve-cluster pve-firmware

# Remove backports
sed -i '/backports/d' /etc/apt/sources.list

# Add pve no-sub repo
echo "deb http://download.proxmox.com/debian jessie pve-no-subscription" >> /etc/apt/sources.list 

# Update distribution in sources and update
sed -i 's/wheezy/jessie/g' /etc/apt/sources.list
sed -i 's/wheezy/jessie/g' /etc/apt/sources.list.d/pve-enterprise.list
apt-get update

# Find and install latest kernel version and firmware package
apt-cache search pve-kernel | sort
apt-get install pve-kernel-4.4.18-1-pve pve-firmware 
 
# Find and install latest kernel headers, matching to the installed pve-kernel
apt-cache search pve-headers | sort
apt-get install pve-headers-4.4.18-1-pve

# Upgrade base system and reboot
apt-get upgrade
apt-get dist-upgrade
shutdown -r now

# Install PVE
apt-get install proxmox-ve