Upgrade LXC Debian 12 to 13 (copy/paste solution)

upgrade_debian_12_to_13.sh

#!/bin/bash
# Update source from bookworm to trixie
sed -i 's/bookworm/trixie/g' /etc/apt/sources.list
apt-get update

# Upgrade to trixie
DEBIAN_FRONTEND=noninteractive apt-get -o Dpkg::Options::="--force-confold" dist-upgrade -y

# Disable services that break in LXC / containers (harmless if not present)
systemctl disable --now systemd-networkd-wait-online.service || true
systemctl disable --now systemd-networkd.service || true
systemctl disable --now ifupdown-wait-online || true

# Install ifupdown2 (better networking stack for LXC/VMs)
apt-get install -y ifupdown2

# Cleanup
apt-get autoremove --purge -y
apt-get clean

reboot

Thanks budy. Quite nice to have this, could've written that my self, but heh, lazyness is the key :D