create-static.sh

#!/bin/bash
# ============================================================
#  create-static.sh — Configure Ethernet to Static IP
#  Supports: Ubuntu 22.04/24.04/26.x (Netplan)
#            Arch Linux (systemd-networkd)
#  Run as root: sudo bash create-static.sh
# ============================================================

set -euo pipefail

RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
CYAN='\033[0;36m'
BOLD='\033[1m'
NC='\033[0m'

# ── Root check ───────────────────────────────────────────────
if [[ $EUID -ne 0 ]]; then
    echo -e "${RED}Error: Please run as root → sudo bash $0${NC}"
    exit 1
fi

# ── Detect distro ────────────────────────────────────────────
detect_distro() {
    if [[ -f /etc/os-release ]]; then
        source /etc/os-release
        echo "${ID,,}"   # lowercase: ubuntu, arch, debian, etc.
    else
        echo "unknown"
    fi
}

DISTRO=$(detect_distro)

case "$DISTRO" in
    ubuntu|debian|linuxmint|pop)  METHOD="netplan" ;;
    arch|manjaro|endeavouros|garuda|centos|cachyos) METHOD="networkd" ;;
    *)
        # Fallback: if netplan binary exists use it, else networkd
        if command -v netplan &>/dev/null; then
            METHOD="netplan"
        elif systemctl is-active --quiet systemd-networkd 2>/dev/null || \
             systemctl is-enabled --quiet systemd-networkd 2>/dev/null; then
            METHOD="networkd"
        else
            echo -e "${RED}Unsupported distro: ${DISTRO}. Cannot auto-detect network manager.${NC}"
            exit 1
        fi
        ;;
esac

echo -e "\n${BOLD}${CYAN}══════════════════════════════════════════${NC}"
echo -e "${BOLD}${CYAN}   Static IP Configurator                  ${NC}"
echo -e "${BOLD}${CYAN}   Distro : ${DISTRO}  │  Method: ${METHOD}  ${NC}"
echo -e "${BOLD}${CYAN}══════════════════════════════════════════${NC}\n"

# ── List ethernet interfaces ─────────────────────────────────
echo -e "${YELLOW}Available network interfaces:${NC}"
mapfile -t IFACES < <(ip -o link show | awk -F': ' '{print $2}' | grep -v lo)
for i in "${!IFACES[@]}"; do
    IFACE="${IFACES[$i]}"
    STATUS=$(ip link show "$IFACE" | grep -o 'state [A-Z]*' | awk '{print $2}')
    CURRENT_IP=$(ip -4 addr show "$IFACE" 2>/dev/null | grep -oP '(?<=inet )\S+' || echo "none")
    echo -e "  ${BOLD}[$((i+1))]${NC} ${CYAN}${IFACE}${NC}  — state: ${STATUS}  IP: ${CURRENT_IP}"
done

echo ""
read -rp "$(echo -e "${BOLD}Select interface number: ${NC}")" IFACE_NUM

if ! [[ "$IFACE_NUM" =~ ^[0-9]+$ ]] || (( IFACE_NUM < 1 || IFACE_NUM > ${#IFACES[@]} )); then
    echo -e "${RED}Invalid selection.${NC}"; exit 1
fi

IFACE="${IFACES[$((IFACE_NUM-1))]}"
echo -e "\n${GREEN}Selected: ${BOLD}${IFACE}${NC}\n"

# ── Helper: validate IPv4 ────────────────────────────────────
valid_ip() {
    local ip="$1"
    local IFS='.'
    read -ra PARTS <<< "$ip"
    [[ ${#PARTS[@]} -eq 4 ]] || return 1
    for part in "${PARTS[@]}"; do
        [[ "$part" =~ ^[0-9]+$ ]] && (( part >= 0 && part <= 255 )) || return 1
    done
}

# ── Collect static IP settings ───────────────────────────────
while true; do
    read -rp "$(echo -e "${BOLD}Static IP address (e.g. 192.168.1.100): ${NC}")" STATIC_IP
    valid_ip "$STATIC_IP" && break
    echo -e "${RED}  Invalid IP. Try again.${NC}"
done

while true; do
    read -rp "$(echo -e "${BOLD}Subnet prefix length (e.g. 24 for /24): ${NC}")" PREFIX
    [[ "$PREFIX" =~ ^[0-9]+$ ]] && (( PREFIX >= 1 && PREFIX <= 32 )) && break
    echo -e "${RED}  Invalid prefix. Enter a number 1-32.${NC}"
done

while true; do
    read -rp "$(echo -e "${BOLD}Default gateway (e.g. 192.168.1.1): ${NC}")" GATEWAY
    valid_ip "$GATEWAY" && break
    echo -e "${RED}  Invalid gateway. Try again.${NC}"
done

read -rp "$(echo -e "${BOLD}DNS servers, space-separated (default: 8.8.8.8 1.1.1.1): ${NC}")" DNS_INPUT
DNS_INPUT="${DNS_INPUT:-8.8.8.8 1.1.1.1}"

# ════════════════════════════════════════════════════════════
#  NETPLAN (Ubuntu / Debian)
# ════════════════════════════════════════════════════════════
apply_netplan() {
    # Build YAML DNS list
    local DNS_YAML=""
    for dns in $DNS_INPUT; do
        DNS_YAML+="          - ${dns}"$'\n'
    done

    local NETPLAN_DIR="/etc/netplan"
    local NETPLAN_FILE="${NETPLAN_DIR}/99-static-${IFACE}.yaml"

    mkdir -p "$NETPLAN_DIR"

    if [[ -f "$NETPLAN_FILE" ]]; then
        local BACKUP="${NETPLAN_FILE}.bak.$(date +%Y%m%d_%H%M%S)"
        cp "$NETPLAN_FILE" "$BACKUP"
        echo -e "${YELLOW}Backed up existing config → ${BACKUP}${NC}"
    fi

    cat > "$NETPLAN_FILE" <<EOF
network:
  version: 2
  renderer: networkd
  ethernets:
    ${IFACE}:
      dhcp4: no
      addresses:
        - ${STATIC_IP}/${PREFIX}
      routes:
        - to: default
          via: ${GATEWAY}
      nameservers:
        addresses:
${DNS_YAML}
EOF

    chmod 600 "$NETPLAN_FILE"
    echo -e "\n${GREEN}Netplan config written to: ${BOLD}${NETPLAN_FILE}${NC}"
    echo -e "\n${YELLOW}Config preview:${NC}"
    echo "─────────────────────────────────────────"
    cat "$NETPLAN_FILE"
    echo "─────────────────────────────────────────"

    echo ""
    read -rp "$(echo -e "${BOLD}Apply now? This will change your network. (y/N): ${NC}")" CONFIRM
    if [[ "$CONFIRM" =~ ^[Yy]$ ]]; then
        echo -e "\n${CYAN}Validating config...${NC}"
        netplan generate 2>&1 || { echo -e "${RED}Config invalid! Rolling back.${NC}"; rm -f "$NETPLAN_FILE"; exit 1; }
        echo -e "${CYAN}Applying...${NC}"
        netplan apply
        sleep 2
        local NEW_IP
        NEW_IP=$(ip -4 addr show "$IFACE" 2>/dev/null | grep -oP '(?<=inet )\S+' || echo "not assigned yet")
        echo -e "\n${GREEN}${BOLD}Done!${NC} ${IFACE} → ${BOLD}${NEW_IP}${NC}"
        echo -e "${YELLOW}Tip: if SSH dropped, reconnect to ${STATIC_IP}${NC}"
    else
        echo -e "\n${YELLOW}Skipped. Apply manually: ${BOLD}sudo netplan apply${NC}"
    fi

    echo -e "\n${CYAN}To revert to DHCP: delete ${NETPLAN_FILE} and run: sudo netplan apply${NC}\n"
}

# ════════════════════════════════════════════════════════════
#  SYSTEMD-NETWORKD (Arch Linux)
# ════════════════════════════════════════════════════════════
apply_networkd() {
    # Build DNS line (space-separated for networkd)
    local DNS_LINE
    DNS_LINE=$(echo "$DNS_INPUT" | tr '\n' ' ' | xargs)

    local NET_DIR="/etc/systemd/network"
    local NET_FILE="${NET_DIR}/20-static-${IFACE}.network"

    mkdir -p "$NET_DIR"

    if [[ -f "$NET_FILE" ]]; then
        local BACKUP="${NET_FILE}.bak.$(date +%Y%m%d_%H%M%S)"
        cp "$NET_FILE" "$BACKUP"
        echo -e "${YELLOW}Backed up existing config → ${BACKUP}${NC}"
    fi

    cat > "$NET_FILE" <<EOF
[Match]
Name=${IFACE}

[Network]
Address=${STATIC_IP}/${PREFIX}
Gateway=${GATEWAY}
DNS=${DNS_LINE}

[Link]
RequiredForOnline=yes
EOF

    chmod 600 "$NET_FILE"
    echo -e "\n${GREEN}systemd-networkd config written to: ${BOLD}${NET_FILE}${NC}"
    echo -e "\n${YELLOW}Config preview:${NC}"
    echo "─────────────────────────────────────────"
    cat "$NET_FILE"
    echo "─────────────────────────────────────────"

    # Also configure systemd-resolved for DNS if available
    if command -v resolvectl &>/dev/null; then
        echo -e "\n${CYAN}Note: systemd-resolved detected — DNS will be managed automatically.${NC}"
    fi

    echo ""
    read -rp "$(echo -e "${BOLD}Apply now? This will restart systemd-networkd. (y/N): ${NC}")" CONFIRM
    if [[ "$CONFIRM" =~ ^[Yy]$ ]]; then
        echo -e "\n${CYAN}Enabling & restarting systemd-networkd...${NC}"

        # Disable any conflicting DHCP service on this interface (NetworkManager, dhcpcd)
        if systemctl is-active --quiet NetworkManager 2>/dev/null; then
            echo -e "${YELLOW}Detected NetworkManager — stopping it for this interface.${NC}"
            nmcli device set "$IFACE" managed no 2>/dev/null || true
        fi
        if systemctl is-active --quiet dhcpcd 2>/dev/null; then
            echo -e "${YELLOW}Stopping dhcpcd (conflicts with networkd)...${NC}"
            systemctl stop dhcpcd
            systemctl disable dhcpcd 2>/dev/null || true
        fi

        systemctl enable systemd-networkd --now
        systemctl restart systemd-networkd

        # Restart resolved if present
        if systemctl list-units --type=service | grep -q systemd-resolved; then
            systemctl enable systemd-resolved --now
            systemctl restart systemd-resolved
        fi

        sleep 3
        local NEW_IP
        NEW_IP=$(ip -4 addr show "$IFACE" 2>/dev/null | grep -oP '(?<=inet )\S+' || echo "not assigned yet")
        echo -e "\n${GREEN}${BOLD}Done!${NC} ${IFACE} → ${BOLD}${NEW_IP}${NC}"
        echo -e "${YELLOW}Tip: if SSH dropped, reconnect to ${STATIC_IP}${NC}"
    else
        echo -e "\n${YELLOW}Skipped. Apply manually:${NC}"
        echo -e "  ${BOLD}sudo systemctl restart systemd-networkd${NC}"
    fi

    echo -e "\n${CYAN}To revert to DHCP: delete ${NET_FILE} and restart systemd-networkd${NC}\n"
}

# ── Dispatch ─────────────────────────────────────────────────
case "$METHOD" in
    netplan)   apply_netplan ;;
    networkd)  apply_networkd ;;
esac