Upgrade Proxmox PVE HN hardware node from version 3.1.x to 3.3.x

*** MAKE SURE ALL CONTAINERS AND VMS ARE SHUTDOWN ***

*** MAKE BACKUP OF ALL CTS AND VMS ***

edit sources.list

nano /etc/apt/sources.list

add the following line in between debian main and debian security:

# PVE pve-no-subscription repository provided by proxmox.com, NOT recommended for production use
deb http://download.proxmox.com/debian wheezy pve-no-subscription

Remark this line to avoid error for subscription repo:

nano /etc/apt/sources.list.d/pve-enterprise.list

# deb https://enterprise.proxmox.com/debian wheezy pve-enterprise

Update packages list

apt-get update

Perform upgrade

apt-get dist-upgrade