Install and configure Nagios Core 4.5 for network and server monitoring with web interface

#!/usr/bin/env bash

set -euo pipefail

# Colors for output
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m'

# Default variables
NAGIOS_VERSION="4.5.5"
PLUGINS_VERSION="2.4.10"
NAGIOS_USER="nagios"
ADMIN_USER="nagiosadmin"

# Usage function
usage() {
    echo "Usage: $0 [OPTIONS]"
    echo "Options:"
    echo "  -h, --help     Show this help message"
    echo "  -p, --password Set admin password (will prompt if not provided)"
    exit 1
}

# Cleanup function
cleanup() {
    echo -e "${RED}[ERROR] Installation failed. Cleaning up...${NC}"
    systemctl stop nagios 2>/dev/null || true
    rm -rf /tmp/nagios-* /tmp/nagios-plugins-* 2>/dev/null || true
    exit 1
}

trap cleanup ERR

# Parse arguments
ADMIN_PASSWORD=""
while [[ $# -gt 0 ]]; do
    case $1 in
        -h|--help)
            usage
            ;;
        -p|--password)
            ADMIN_PASSWORD="$2"
            shift 2
            ;;
        *)
            echo -e "${RED}Unknown option: $1${NC}"
            usage
            ;;
    esac
done

# Check if running as root or with sudo
if [[ $EUID -ne 0 ]]; then
    echo -e "${RED}This script must be run as root or with sudo${NC}"
    exit 1
fi

# Auto-detect distribution
if [ -f /etc/os-release ]; then
    . /etc/os-release
    case "$ID" in
        ubuntu|debian)
            PKG_MGR="apt"
            PKG_INSTALL="apt install -y"
            PKG_UPDATE="apt update && apt upgrade -y"
            WEB_USER="www-data"
            WEB_SERVICE="apache2"
            APACHE_CONF_DIR="/etc/apache2/sites-enabled"
            ;;
        almalinux|rocky|centos|rhel|ol|fedora)
            PKG_MGR="dnf"
            PKG_INSTALL="dnf install -y"
            PKG_UPDATE="dnf update -y"
            WEB_USER="apache"
            WEB_SERVICE="httpd"
            APACHE_CONF_DIR="/etc/httpd/conf.d"
            ;;
        amzn)
            PKG_MGR="yum"
            PKG_INSTALL="yum install -y"
            PKG_UPDATE="yum update -y"
            WEB_USER="apache"
            WEB_SERVICE="httpd"
            APACHE_CONF_DIR="/etc/httpd/conf.d"
            ;;
        *)
            echo -e "${RED}Unsupported distribution: $ID${NC}"
            exit 1
            ;;
    esac
else
    echo -e "${RED}Cannot detect distribution${NC}"
    exit 1
fi

echo -e "${GREEN}Installing Nagios Core 4.5 on $PRETTY_NAME${NC}"

# Step 1: Update system packages
echo -e "${YELLOW}[1/10] Updating system packages...${NC}"
$PKG_UPDATE

# Step 2: Install dependencies
echo -e "${YELLOW}[2/10] Installing dependencies...${NC}"
if [[ "$PKG_MGR" == "apt" ]]; then
    $PKG_INSTALL apache2 apache2-utils php php-gd libgd-dev build-essential unzip wget openssl libssl-dev
else
    $PKG_INSTALL httpd php php-gd gd-devel unzip wget openssl-devel
    dnf groupinstall -y "Development Tools" 2>/dev/null || yum groupinstall -y "Development Tools"
fi

# Step 3: Create Nagios user and group
echo -e "${YELLOW}[3/10] Creating Nagios user and group...${NC}"
if ! id "$NAGIOS_USER" &>/dev/null; then
    useradd -r -s /bin/false "$NAGIOS_USER"
fi
usermod -aG "$NAGIOS_USER" "$WEB_USER"

# Step 4: Download and compile Nagios Core
echo -e "${YELLOW}[4/10] Downloading and compiling Nagios Core...${NC}"
cd /tmp
wget -q "https://assets.nagios.com/downloads/nagioscore/releases/nagios-${NAGIOS_VERSION}.tar.gz"
tar -xzf "nagios-${NAGIOS_VERSION}.tar.gz"
cd "nagios-${NAGIOS_VERSION}"

./configure --with-httpd-conf="$APACHE_CONF_DIR" \
  --with-nagios-user="$NAGIOS_USER" \
  --with-nagios-group="$NAGIOS_USER" \
  --with-command-user="$NAGIOS_USER" \
  --with-command-group="$NAGIOS_USER" >/dev/null

make all >/dev/null
make install >/dev/null
make install-daemoninit >/dev/null
make install-commandmode >/dev/null
make install-config >/dev/null
make install-webconf >/dev/null

# Step 5: Download and install Nagios plugins
echo -e "${YELLOW}[5/10] Installing Nagios plugins...${NC}"
cd /tmp
wget -q "https://github.com/nagios-plugins/nagios-plugins/releases/download/release-${PLUGINS_VERSION}/nagios-plugins-${PLUGINS_VERSION}.tar.gz"
tar -xzf "nagios-plugins-${PLUGINS_VERSION}.tar.gz"
cd "nagios-plugins-${PLUGINS_VERSION}"

./configure --with-nagios-user="$NAGIOS_USER" --with-nagios-group="$NAGIOS_USER" >/dev/null
make >/dev/null
make install >/dev/null

# Step 6: Configure Apache web server
echo -e "${YELLOW}[6/10] Configuring Apache web server...${NC}"
if [[ "$PKG_MGR" == "apt" ]]; then
    a2enmod rewrite cgi >/dev/null
    systemctl restart apache2
else
    systemctl enable httpd
    systemctl start httpd
    # Configure SELinux for Nagios
    if command -v setsebool &>/dev/null; then
        setsebool -P httpd_can_network_connect 1
        setsebool -P httpd_enable_cgi 1
    fi
fi

# Step 7: Create Nagios admin user
echo -e "${YELLOW}[7/10] Creating Nagios admin user...${NC}"
if [[ -z "$ADMIN_PASSWORD" ]]; then
    echo "Enter password for Nagios admin user ($ADMIN_USER):"
    read -s ADMIN_PASSWORD
fi
echo "$ADMIN_PASSWORD" | htpasswd -c -i /usr/local/nagios/etc/htpasswd.users "$ADMIN_USER"

# Step 8: Configure file permissions
echo -e "${YELLOW}[8/10] Setting file permissions...${NC}"
chown -R "$NAGIOS_USER":"$NAGIOS_USER" /usr/local/nagios/
chmod 755 /usr/local/nagios/var/rw
find /usr/local/nagios/etc -name "*.cfg" -exec chmod 644 {} \;

# Step 9: Configure Nagios main configuration
echo -e "${YELLOW}[9/10] Configuring Nagios...${NC}"
cat >> /usr/local/nagios/etc/nagios.cfg << 'EOF'

# Web interface settings
check_external_commands=1
command_check_interval=10s

# Log settings  
log_initial_states=1
log_current_states=1
EOF

# Enable and start services
systemctl enable nagios
systemctl start nagios
systemctl enable "$WEB_SERVICE"
systemctl restart "$WEB_SERVICE"

# Configure firewall
if command -v ufw &>/dev/null && ufw status | grep -q "Status: active"; then
    ufw allow 'Apache Full' >/dev/null 2>&1 || true
elif command -v firewall-cmd &>/dev/null; then
    firewall-cmd --permanent --add-service=http >/dev/null 2>&1 || true
    firewall-cmd --permanent --add-service=https >/dev/null 2>&1 || true
    firewall-cmd --reload >/dev/null 2>&1 || true
fi

# Step 10: Verify installation
echo -e "${YELLOW}[10/10] Verifying installation...${NC}"
if systemctl is-active --quiet nagios && systemctl is-active --quiet "$WEB_SERVICE"; then
    HOSTNAME=$(hostname -f 2>/dev/null || hostname)
    echo -e "${GREEN}✓ Nagios Core installation completed successfully!${NC}"
    echo -e "${GREEN}✓ Web interface available at: http://$HOSTNAME/nagios${NC}"
    echo -e "${GREEN}✓ Login with username: $ADMIN_USER${NC}"
    echo -e "${GREEN}✓ Services are running and enabled${NC}"
else
    echo -e "${RED}✗ Installation completed but services may not be running properly${NC}"
    exit 1
fi

# Cleanup temp files
rm -rf /tmp/nagios-* /tmp/nagios-plugins-*

echo -e "${YELLOW}Note: Configure your hosts and services in /usr/local/nagios/etc/objects/${NC}"