enable-dhcp.sh

enable-dhcp.sh

#!/usr/bin/env bash

set -e

NETPLAN_FILE="/etc/netplan/50-cloud-init.yaml"
BACKUP_FILE="/etc/netplan/50-cloud-init.yaml.bak.$(date +%s)"

# Must be run as root
if [[ $EUID -ne 0 ]]; then
  echo "Run as root"
  exit 1
fi

# Ensure file exists
if [[ ! -f "$NETPLAN_FILE" ]]; then
  echo "File not found: $NETPLAN_FILE"
  exit 1
fi

# Detect primary interface (first non-lo interface)
IFACE=$(ip -o link show | awk -F': ' '{print $2}' | grep -v lo | head -n 1)

if [[ -z "$IFACE" ]]; then
  echo "Could not detect network interface"
  exit 1
fi

echo "Detected interface: $IFACE"

# Backup
cp "$NETPLAN_FILE" "$BACKUP_FILE"
echo "Backup created: $BACKUP_FILE"

# Rewrite netplan with DHCP enabled
cat > "$NETPLAN_FILE" <<EOF
network:
  version: 2
  ethernets:
    $IFACE:
      dhcp4: true
EOF

# Apply netplan
netplan apply

echo "DHCP enabled on $IFACE"