Quick deployment of Debian cloud image in Proxmox with cloud-init

Introduction

This post demonstrates how to quickly create and afterwards clone virtual machine in Proxmox using Debian cloud image. When not using cloud image, more time must be spent after cloning virtual machine: you need to recreate SSH keys (cloning virtual machine doesn't change host SSH keys and that can cause problems with SSH connection to VMs cloned from same template machine), create new user with SSH access, change partition size when you resize disk in Proxmox, set hostname. All of this can be easily achieved with Debian cloud image because it is using cloud-init and Proxmox has built in support for it. This instruction is for creating virtual machine from cloud image on Proxmox with ZFS filesystem.

Software used: Proxmox 8, Debian 12 cloud image

General info

Warning

One important thing to note is that by default Proxmox cloud-init configuration sets up sudo command in the virtual machine so that it does not require entering a password. Machines with such configuration are suitable for testing, automation, CI/CD and even then it's recommended to restrict what actions user can do with sudo without password. You can change this behavior with custom cloud-init configuration, but this requires creating new files that you must manage outside of Proxmox backup system. Such configuration is beyond the scope of this post.

Download Debian cloud image

Create ZFS dataset in Proxmox for downloading cloud images.

# zfs create datapool/cloud-images -o recordsize=1M

datapool - your ZFS zpool name
cloud-images - enter name for your dataset
-o recordsize - ZFS dataset record size, for large files like backups and ISO images 1M can be a good choice

Download latest cloud image in raw format from Debian Official Cloud Images web page (for Debian 12 it will be in bookworm path).

In this post genericcloud cloud image will be used.

wget -P /path/to/save/ https://URL/image.raw

# wget -P /datapool/cloud-images/ https://cloud.debian.org/images/cloud/bookworm/<date-time>/debian-12-genericcloud-amd64-<date-time>.raw

-P - folder where the file will be downloaded

Note

Debian web page has following cloud image types:

generic: Should run in any environment using cloud-init, for e.g. OpenStack, DigitalOcean and also on bare metal.
genericcloud: Similar to generic. Should run in any virtualised environment. Is smaller than generic by excluding drivers for physical hardware.
nocloud: Mostly useful for testing the build process itself. Doesn't have cloud-init installed, but instead allows root login without a password.
azure: Optimized for the Microsoft Azure environment
ec2: Optimized for the Amazon EC2

Create virtual machine

Create a new virtual machine in Proxmox without assigning a virtual disk.

Click button Create VM:
- Tab General:
  - Node - select your Proxmox host
  - VM ID - enter ID for your virtual machine (in Proxmox it is a number)
  - Name - enter name for your virtual machine, it will be your machine hostname
- Tab OS:
  - select Do not use any media
  - in other fields leave default values
- Tab System:
  - Qemu Agent - check this field
  - in other fields leave default values
- Tab Disks:
  - delete default disk scsci0
- Tab CPU:
  - Cores - select number of cores you want to assign to virtual machine
  - Type - select host if you want maximum performance
  - in other fields leave default values
- Tab Memory:
  - Memory (MiB) - enter amount of RAM you want to assign to virtual machine
- Tab Network:
  - Bridge - select network bridge for use by this virtual machine
  - VLAN Tag - enter VLAN number if you separate virtual machines from other parts of your network using VLANs. If you don't use VLANs leave this field empty.
  - in other fields leave default values

Import Debian cloud image to Proxmox virtual machine

Import downloaded cloud image using command:

qm disk import <vmID> <image_file> <Proxmox_storage>

# qm disk import 100 /datapool/cloud-images/debian-12-genericcloud-amd64-xxx.raw local-zfs

100 - ID of created virtual machine in Proxomx
local-zfs - storage in Proxmox to which import downloaded cloud image as virtual machine disk

Next go to created virtual machine:

Datacenter > your Proxmox host > virtual machine > Hardware > select Unused Disk 0 > click Edit > check Discard > click Add
Datacenter > your Proxmox host > virtual machine > Options > select Boot Order > click Edit > check scsci0 and drag and drop it as first disk to boot

Discard - discard unused blocks on mounted filesystem. This can save space on host when you delete data from virtual machine, because image can then be automatically shrunk.

Configuration of Debian virtual machine

Remove hardware not needed by virtual machine

You can remove CD/DVD drive as it won't be needed by this machine.

Datacenter > your Proxmox host > virtual machine > Hardware > select CD/DVD drive > click Remove

Resize disk

Datacenter > your Proxmox host > virtual machine > Hardware > select Hard Disk (scsi0) > click Disk Action > select Resize > Size Increment (GiB) - enter number in gigabytes by how much to increase the disk

Cloud-init

Datacenter > your Proxmox host > virtual machine > Hardware > click Add > select CloudInit Drive > Storage - select storage where you keep your virtual machine
Datacenter > your Proxmox host > virtual machine > Cloud-Init:
- User - create user for this virtual machine
- Password - set user password for this virtual machine
- SSH public key - load SSH public key for SSH login to this virtual machine
- IP Config (net0) - set IPv4 as DHCP if you plan on using DHCP for this virtual machine or enter static IP address
- in other fields leave default values

You can change above CloudInit values at any time and they will be included at the next virtual machine reboot. If you resize virtual machine disk size, it will be expanded in virtual machine at the next reboot.

Cloning virtual machine

Tip

If you plan to clone virtual machine in Proxmox that was created with cloud image it is best to clone it before first start. Otherwise if you run this VM, cloud-init will set some settings that are only set on first boot. This can result in the cloned machine receiving the same IP address from the DHCP server as the base virtual machine.

First run of Debian virtual machine

Start your virtual machine in Proxmox. If everything was configured correctly you should see login screen in virtual machine Console:

Datacenter > your Proxmox host > virtual machine > Console

Enter credentials that you configured in CloudInit to log in.

Note

By default Proxmox CloudInit configure sudo command in virtual machine to don't require entering a password.
This configuration is read from read-only file: /etc/sudoers.d/90-cloud-init-users.

Check assigned IP

Check if IP is assigned by running command:

$ ip a

Other actions

With the virtual machine up and running you need to perform other typical post install actions such as:

Set timezone
Install qemu-guest-agent
Create swapfile
Create other users