debian-12-cloudimage.sh

# This documents how you would take a Debian 12 cloud image and make a Proxmox template out of it.
# This script isn't really meant to be executed, but more as a reference and copy/paste for each step.
# Enjoy!


# Download the image
mkdir -p ~/debian-bookworm-build/original && cd ~/debian-bookworm-build/original
wget 'https://cloud.debian.org/images/cloud/bookworm/20240717-1811/debian-12-genericcloud-amd64-20240717-1811.qcow2'
cd ..

# This is what the file systems in that image look like, for reference:
#
# $ virt-filesystems --long --parts --blkdevs -h -a debian-12-genericcloud-amd64-20240717-1811.qcow2
# Name        Type       MBR  Size  Parent
# /dev/sda1   partition  -    1.9G  /dev/sda
# /dev/sda14  partition  -    3.0M  /dev/sda
# /dev/sda15  partition  -    124M  /dev/sda
# /dev/sda    device     -    2.0G  -


# Resize the image, to give us more space to work with.
# The image is 2GB by default (seen above), but I'd like at least 8GB

qemu-img create -f qcow2 -o preallocation=metadata bookworm-cloudimg-amd64-8G.qcow2 8G
virt-resize --expand /dev/sda1 original/debian-12-genericcloud-amd64-20240717-1811.qcow2 bookworm-cloudimg-amd64-8G.qcow2

# Setup the image

# This will do a few things...
# * Reinstall grub, required because virt-resize messes up the partitions and the image won't boot, see:
#   https://bugzilla.redhat.com/show_bug.cgi?id=1472039
#   https://news.ycombinator.com/item?id=16304781
# * Install cloud guest packages
# * Install the qemu guest agent (so Proxmox can communicate to the guest), and enable it.
# * And install a base layer of packages that I like...
#   * cifs-utils are for connecting to my SMB file share
#   * htop and tmux are nice to have

virt-customize -a bookworm-cloudimg-amd64-8G.qcow2 \
    --run-command 'grub-install /dev/sda' \
    --install cloud-guest-utils,cloud-initramfs-growroot \
    --install qemu-guest-agent \
    --run-command 'systemctl enable qemu-guest-agent' \
    --install cifs-utils,htop,tmux

# Re-shrink the image after we made our changes:
virt-sparsify --compress bookworm-cloudimg-amd64-8G.qcow2 bookworm-cloudimg-amd64-8G-small.qcow2
rm bookworm-cloudimg-amd64-8G.qcow2

#
# Now the image is ready to go, and we can add it to Proxmox as a template!
#
# *** From root user on the Proxmox host: ***
# 

# Create the VM
qm create 9020 \
    --name 'Debian-12-20240717-ready' \
    --ostype l26 \
    --memory 2048 \
    --cores 2 \
    --net0 virtio,bridge=vmbr0 \
    --scsihw virtio-scsi-single \
    --agent enabled=1,fstrim_cloned_disks=1

# Copy over image
qm set 9020 --scsi0 local-vmdata:0,import-from=/home/ryan/debian-bookworm-build/bookworm-cloudimg-amd64-8G-small.qcow2

# Start configuring cloud-init data
qm set 9020 --ide2 local-vmdata:cloudinit --boot order=scsi0 --serial0 socket --vga serial0

# Convert VM to template to begin using
qm template 9020

# Now you can clone it from the Proxmox web UI and make VMs :)