Mastering DNS Automation with Bash 🔄

#!/bin/bash

# Configuration
PRIMARY_DNS="8.8.8.8"
SECONDARY_DNS="8.8.4.4"
RESOLV_CONF="/etc/resolv.conf"
BACKUP_DIR="/etc/dns_backups"

# Ensure running as root
if [ "$EUID" -ne 0 ]; then
    echo "Please run as root"
    exit 1
fi

# Create backup directory if it doesn't exist
mkdir -p "$BACKUP_DIR"

# Backup with timestamp
timestamp=$(date +%Y%m%d_%H%M%S)
cp "$RESOLV_CONF" "${BACKUP_DIR}/resolv.conf.${timestamp}"

# Function to validate IP address
validate_ip() {
    local ip=$1
    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        return 0
    fi
    return 1
}

# Validate DNS servers
if ! validate_ip "$PRIMARY_DNS" || ! validate_ip "$SECONDARY_DNS"; then
    echo "Invalid IP address format for DNS servers"
    exit 1
fi

# Write new configuration
cat <<EOL > "$RESOLV_CONF"
# Generated by DNS automation script on $(date)
nameserver $PRIMARY_DNS
nameserver $SECONDARY_DNS
options timeout:2 attempts:3
EOL

# Test DNS resolution
if ! ping -c 1 google.com >/dev/null 2>&1; then
    echo "WARNING: DNS resolution test failed"
    echo "Restoring backup..."
    cp "${BACKUP_DIR}/resolv.conf.${timestamp}" "$RESOLV_CONF"
    exit 1
fi

echo "DNS configuration updated successfully!"

#!/bin/bash

HOSTS_FILE="/etc/hosts"
BACKUP_DIR="/etc/dns_backups"

# Function to add a host entry
add_host() {
    local ip=$1
    local hostname=$2

    # Check if entry already exists
    if grep -q "^$ip.*$hostname" "$HOSTS_FILE"; then
        echo "Entry already exists"
        return 1
    fi

    # Add new entry
    echo "$ip $hostname" >> "$HOSTS_FILE"
    echo "Added $hostname ($ip)"
}

# Function to remove a host entry
remove_host() {
    local hostname=$1
    sed -i "/[[:space:]]${hostname}$/d" "$HOSTS_FILE"
    echo "Removed $hostname"
}

# Function to list all custom entries
list_hosts() {
    echo "Current host entries:"
    grep -v "^#" "$HOSTS_FILE" | grep -v "^$"
}

# Main script logic
case "$1" in
    "add")
        add_host "$2" "$3"
        ;;
    "remove")
        remove_host "$2"
        ;;
    "list")
        list_hosts
        ;;
    *)
        echo "Usage: $0 {add|remove|list} [ip] [hostname]"
        exit 1
        ;;
esac

#!/bin/bash

# Configuration
ZONE="example.com"
TTL=300
KEY_FILE="/etc/bind/ddns.key"
DNS_SERVER="ns1.example.com"

# Function to update DNS record
update_record() {
    local record_name=$1
    local record_type=$2
    local record_value=$3

    nsupdate -k "$KEY_FILE" <<EOF
server $DNS_SERVER
zone $ZONE
update delete $record_name.$ZONE $record_type
update add $record_name.$ZONE $TTL $record_type $record_value
send
EOF

    if [ $? -eq 0 ]; then
        echo "Successfully updated $record_name.$ZONE"
    else
        echo "Failed to update DNS record"
        return 1
    fi
}

# Example usage
update_record "www" "A" "192.168.1.100"
update_record "mail" "MX" "10 mail.example.com."