vultr-startup-debian-ubuntu.sh

#!/bin/bash

upgrade() {
# Initial updates
apt update
apt upgrade -y
DEBIAN_FRONTEND=noninteractive apt-get -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" upgrade

apt install -y jq
apt install -y ipcalc
snap install yq
}

calculate_mask() {
    MASK=`ipcalc -n 1.1.1.1 $1 | sed -n '/^Netm/{s#.*= #/#;s/ .*//p;q}'`
}

configure_private_ip() {
    curl -o /tmp/metadata.json http://169.254.169.254/v1.json
    PRIVATE_IP=`cat /tmp/metadata.json | jq '.interfaces[1].ipv4.address' -r`
    NET_MASK=`cat /tmp/metadata.json | jq '.interfaces[1].ipv4.netmask' -r`
    calculate_mask $NET_MASK
    jq -n --arg ip_cidr "$PRIVATE_IP$MASK"  '{"network": {"version": 2, "renderer": "networkd", "ethernets": {"ens7": {"dhcp4": "no", "mtu": 1450, "addresses": [$ip_cidr]}}}}' > /tmp/01-netcfg.json
    cat /tmp/01-netcfg.json | yq r - > /etc/netplan/01-netcfg.yaml
    netplan apply

}

upgrade
configure_private_ip

Upgrade the system and configures private network with the vultr api. You can see the ip in the settings tab of your server.
It may take a few minutes to finish the upgrade