Upgrade a 4.x Installation using a newer ISO image
Introduction
If you have a valid subscription the upgrade process should be as easy as upgrading packages, i.e.
apt-get update && apt-get dist-upgrade
If you are just testing the Proxmox VE 4.0 without a valid subscription you have no access to the pve-enterprise repository so you cannot easily ugrade to 4.1. To avoid a new installation, you can use the distribution ISO image to update the packages.
Step by step upgrade process
Create a mount point and update /etc/fstab accordingly
mkdir /media/cdrom echo '/dev/sr0 /media/cdrom iso9660 noauto,ro 0 0' >> /etc/fstab # optional
Mount the CD or an ISO image
If you have a real CD/DVD or if running the Proxmox VE in another VM and using the ISO image:
mount /dev/sr0 /media/cdrom
or just (if you have an entry in the /etc/fstab):
mount /media/cdrom
If you have the downloaded ISO image:
mount -o loop /path/to/proxmox-ve_4.1-2f9650d4-21.iso /media/cdrom
Mount an empty directory over /media/cdrom/dev
Using apt-cdrom will fail while trying to scan /media/cdrom/dev/proc/self/fd directory. As a workaround create an empty file-system and mount it over /media/cdrom/dev:
mkfs.cramfs /mnt /tmp/empty-image.img # /mnt being an empty directory mount -o loop /tmp/empty-image.img /media/cdrom/dev ls -l /media/cdrom/dev # shows an empty content
Add a CD repository
apt-cdrom --no-auto-detect --cdrom /media/cdrom --no-mount add
This should scan the CD content, ask you for a name (use Proxmox 4.1) and add a repository in your /etc/apt/sources.list file. It creates also an entry in the /var/lib/apt/cdroms.list using the CD ID and given name. The content of the /var/lib/apt/cdroms.list should look like:
CD::aa2253e1b6b98e93b17b38bef5b4d256-2 "Proxmox 4.1";
The added lines to the /etc/apt.sources.list should look like:
deb cdrom:[Proxmox 4.1]/ jessie pve deb cdrom:[Proxmox 4.1]/proxmox/packages/ /
Update and upgrade packages
apt-get update && apt-get dist-upgrade
Reboot
systemctl reboot
The packages should be updated from the CD/ISO image, a new kernel version should be 4.2.6-1-pve.
Cleanup: Remove the CD repository
You can disable or remove the CD repository by commenting out the corresponding lines in the /etc/apt/sources.list file, you can also remove the /var/lib/apt/cdroms.list file. Run apt-get update afterwards.