diff --git a/.rubocop.yml b/.rubocop.yml
index b7dc82c..9d4e4ab 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -6,8 +6,51 @@ AllCops:
 Gemspec/OrderedDependencies:
   Enabled: false
 
+# allows nicer usage of private_class_method
+Layout/EmptyLinesAroundArguments:
+  Enabled: false
+
+Layout/SpaceInsideHashLiteralBraces:
+  Enabled: false
+
+Metrics/AbcSize:
+  Enabled: false
+
+Metrics/BlockLength:
+  Enabled: false
+
+Metrics/ClassLength:
+  Enabled: false
+
 Metrics/LineLength:
   Max: 200
 
+Metrics/MethodLength:
+  Enabled: false
+
+Style/ConditionalAssignment:
+  Enabled: false
+
 Style/Documentation:
   Enabled: false
+
+Style/FormatStringToken:
+  Enabled: false
+
+Style/FrozenStringLiteralComment:
+  Enabled: false
+
+Style/GuardClause:
+  Enabled: false
+
+Style/IdenticalConditionalBranches:
+  Enabled: false
+
+Style/InverseMethods:
+  Enabled: false
+
+Style/NegatedIf:
+  Enabled: false
+
+Style/SymbolArray:
+  Enabled: false
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index f097309..6f945a4 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -1,308 +1,7 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2018-02-23 11:13:02 +0100 using RuboCop version 0.52.1.
+# on 2018-02-23 12:54:10 +0100 using RuboCop version 0.52.1.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: AllowForAlignment, ForceEqualSignAlignment.
-Layout/ExtraSpacing:
-  Exclude:
-    - 'dyndnsd.gemspec'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Layout/SpaceAfterComma:
-  Exclude:
-    - 'lib/dyndnsd/generator/bind.rb'
-
-# Offense count: 3
-# Cop supports --auto-correct.
-# Configuration parameters: AllowForAlignment.
-Layout/SpaceAroundOperators:
-  Exclude:
-    - 'dyndnsd.gemspec'
-
-# Offense count: 38
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle, EnforcedStyleForEmptyBraces.
-# SupportedStyles: space, no_space, compact
-# SupportedStylesForEmptyBraces: space, no_space
-Layout/SpaceInsideHashLiteralBraces:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/responder/dyndns_style.rb'
-    - 'lib/dyndnsd/responder/rest_style.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: final_newline, final_blank_line
-Layout/TrailingBlankLines:
-  Exclude:
-    - 'spec/support/dummy_database.rb'
-
-# Offense count: 8
-# Cop supports --auto-correct.
-Layout/TrailingWhitespace:
-  Exclude:
-    - 'lib/dyndnsd/database.rb'
-    - 'lib/dyndnsd/updater/command_with_bind_zone.rb'
-    - 'spec/support/dummy_database.rb'
-
-# Offense count: 4
-Lint/IneffectiveAccessModifier:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Lint/ScriptPermission:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 5
-# Cop supports --auto-correct.
-# Configuration parameters: AllowUnusedKeywordArguments, IgnoreEmptyMethods.
-Lint/UnusedMethodArgument:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/responder/dyndns_style.rb'
-    - 'lib/dyndnsd/responder/rest_style.rb'
-
-# Offense count: 1
-Lint/UselessAssignment:
-  Exclude:
-    - 'spec/daemon_spec.rb'
-
-# Offense count: 5
-Metrics/AbcSize:
-  Max: 31
-
-# Offense count: 1
-# Configuration parameters: CountComments, ExcludedMethods.
-Metrics/BlockLength:
-  Max: 159
-
-# Offense count: 1
-# Configuration parameters: CountComments.
-Metrics/ClassLength:
-  Max: 149
-
-# Offense count: 6
-# Configuration parameters: CountComments.
-Metrics/MethodLength:
-  Max: 19
-
-# Offense count: 2
-Naming/AccessorMethodName:
-  Exclude:
-    - 'lib/dyndnsd/responder/dyndns_style.rb'
-    - 'lib/dyndnsd/responder/rest_style.rb'
-
-# Offense count: 3
-# Configuration parameters: NamePrefix, NamePrefixBlacklist, NameWhitelist, MethodDefinitionMacros.
-# NamePrefix: is_, has_, have_
-# NamePrefixBlacklist: is_, has_, have_
-# NameWhitelist: is_a?
-# MethodDefinitionMacros: define_method, define_singleton_method
-Naming/PredicateName:
-  Exclude:
-    - 'spec/**/*'
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/helper.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: AutoCorrect.
-Security/JSONLoad:
-  Exclude:
-    - 'lib/dyndnsd/database.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Security/YAMLLoad:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 4
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: always, conditionals
-Style/AndOr:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Style/ColonMethodCall:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 3
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle, SingleLineConditionsOnly, IncludeTernaryExpressions.
-# SupportedStyles: assign_to_condition, assign_inside_condition
-Style/ConditionalAssignment:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/database.rb'
-
-# Offense count: 2
-# Cop supports --auto-correct.
-Style/DefWithParentheses:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: format, sprintf, percent
-Style/FormatString:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 3
-# Configuration parameters: .
-# SupportedStyles: annotated, template, unannotated
-Style/FormatStringToken:
-  EnforcedStyle: unannotated
-
-# Offense count: 15
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: when_needed, always, never
-Style/FrozenStringLiteralComment:
-  Exclude:
-    - 'Gemfile'
-    - 'Rakefile'
-    - 'dyndnsd.gemspec'
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/database.rb'
-    - 'lib/dyndnsd/generator/bind.rb'
-    - 'lib/dyndnsd/helper.rb'
-    - 'lib/dyndnsd/responder/dyndns_style.rb'
-    - 'lib/dyndnsd/responder/rest_style.rb'
-    - 'lib/dyndnsd/updater/command_with_bind_zone.rb'
-    - 'lib/dyndnsd/version.rb'
-    - 'spec/daemon_spec.rb'
-    - 'spec/spec_helper.rb'
-    - 'spec/support/dummy_database.rb'
-    - 'spec/support/dummy_updater.rb'
-
-# Offense count: 2
-# Configuration parameters: MinBodyLength.
-Style/GuardClause:
-  Exclude:
-    - 'lib/dyndnsd/responder/dyndns_style.rb'
-    - 'lib/dyndnsd/responder/rest_style.rb'
-
-# Offense count: 3
-# Cop supports --auto-correct.
-# Configuration parameters: UseHashRocketsWithSymbolValues, PreferHashRocketsForNonAlnumEndingSymbols.
-# SupportedStyles: ruby19, hash_rockets, no_mixed_keys, ruby19_no_mixed_keys
-Style/HashSyntax:
-  EnforcedStyle: hash_rockets
-
-# Offense count: 2
-Style/IdenticalConditionalBranches:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: InverseMethods, InverseBlocks.
-Style/InverseMethods:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Style/MethodCallWithoutArgsParentheses:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Style/MutableConstant:
-  Exclude:
-    - 'lib/dyndnsd/version.rb'
-
-# Offense count: 6
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: both, prefix, postfix
-Style/NegatedIf:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/helper.rb'
-
-# Offense count: 8
-# Cop supports --auto-correct.
-Style/Not:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/helper.rb'
-
-# Offense count: 6
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: short, verbose
-Style/PreferredHashMethods:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/responder/dyndns_style.rb'
-    - 'lib/dyndnsd/responder/rest_style.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-Style/RedundantBegin:
-  Exclude:
-    - 'lib/dyndnsd/helper.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: AllowAsExpressionSeparator.
-Style/Semicolon:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-
-# Offense count: 2
-# Cop supports --auto-correct.
-# Configuration parameters: .
-# SupportedStyles: use_perl_names, use_english_names
-Style/SpecialGlobalVars:
-  EnforcedStyle: use_perl_names
-
-# Offense count: 80
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle, ConsistentQuotesInMultiline.
-# SupportedStyles: single_quotes, double_quotes
-Style/StringLiterals:
-  Exclude:
-    - 'dyndnsd.gemspec'
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/generator/bind.rb'
-    - 'lib/dyndnsd/responder/dyndns_style.rb'
-    - 'lib/dyndnsd/responder/rest_style.rb'
-    - 'lib/dyndnsd/version.rb'
-    - 'spec/daemon_spec.rb'
-
-# Offense count: 1
-# Cop supports --auto-correct.
-# Configuration parameters: MinSize.
-# SupportedStyles: percent, brackets
-Style/SymbolArray:
-  EnforcedStyle: brackets
-
-# Offense count: 2
-# Cop supports --auto-correct.
-# Configuration parameters: IgnoredMethods.
-# IgnoredMethods: respond_to, define_method
-Style/SymbolProc:
-  Exclude:
-    - 'lib/dyndnsd.rb'
-    - 'lib/dyndnsd/database.rb'
diff --git a/Rakefile b/Rakefile
index ff8bf7c..ecebef6 100644
--- a/Rakefile
+++ b/Rakefile
@@ -5,4 +5,4 @@ require 'rubocop/rake_task'
 RSpec::Core::RakeTask.new(:spec)
 RuboCop::RakeTask.new
 
-task :default => [:rubocop, :spec]
+task default: [:rubocop, :spec]
diff --git a/dyndnsd.gemspec b/dyndnsd.gemspec
index 376d0ae..27fd10c 100644
--- a/dyndnsd.gemspec
+++ b/dyndnsd.gemspec
@@ -1,19 +1,19 @@
 
-$:.push File.expand_path("../lib", __FILE__)
+$LOAD_PATH.push File.expand_path('../lib', __FILE__)
 
 require 'dyndnsd/version'
 
 Gem::Specification.new do |s|
-  s.name  = 'dyndnsd'
+  s.name = 'dyndnsd'
   s.version = Dyndnsd::VERSION
   s.summary = 'dyndnsd.rb'
   s.description = 'A small, lightweight and extensible DynDNS server written with Ruby and Rack.'
-  s.author  = 'Christian Nicolai'
+  s.author = 'Christian Nicolai'
   s.email = 'chrnicolai@gmail.com'
-  s.homepage  = 'https://github.com/cmur2/dyndnsd'
+  s.homepage = 'https://github.com/cmur2/dyndnsd'
   s.license = 'Apache-2.0'
 
-  s.files = `git ls-files`.split($/)
+  s.files = `git ls-files`.split($INPUT_RECORD_SEPARATOR)
   s.test_files = s.files.grep(%r{^(test|spec|features)/})
   s.require_paths = ['lib']
   s.executables = ['dyndnsd']
diff --git a/lib/dyndnsd.rb b/lib/dyndnsd.rb
old mode 100644
new mode 100755
index efc5cb4..3910f07
--- a/lib/dyndnsd.rb
+++ b/lib/dyndnsd.rb
@@ -27,8 +27,8 @@ module Dyndnsd
   end
 
   class LogFormatter
-    def call(lvl, time, progname, msg)
-      "[%s] %-5s %s\n" % [Time.now.strftime('%Y-%m-%d %H:%M:%S'), lvl, msg.to_s]
+    def call(lvl, _time, _progname, msg)
+      format("[%s] %-5s %s\n", Time.now.strftime('%Y-%m-%d %H:%M:%S'), lvl, msg.to_s)
     end
   end
 
@@ -42,12 +42,15 @@ module Dyndnsd
       @db.load
       @db['serial'] ||= 1
       @db['hosts'] ||= {}
-      (@db.save; @updater.update(@db)) if @db.changed?
+      if @db.changed?
+        @db.save
+        @updater.update(@db)
+      end
     end
 
-    def is_authorized?(username, password)
-      allow = ((@users.has_key? username) and (@users[username]['password'] == password))
-      if not allow
+    def authorized?(username, password)
+      allow = ((@users.key? username) && (@users[username]['password'] == password))
+      if !allow
         Dyndnsd.logger.warn "Login failed for #{username}"
         Metriks.meter('requests.auth_failed').mark
       end
@@ -55,40 +58,40 @@ module Dyndnsd
     end
 
     def call(env)
-      return [422, {'X-DynDNS-Response' => 'method_forbidden'}, []] if env["REQUEST_METHOD"] != "GET"
-      return [422, {'X-DynDNS-Response' => 'not_found'}, []] if env["PATH_INFO"] != "/nic/update"
+      return [422, {'X-DynDNS-Response' => 'method_forbidden'}, []] if env['REQUEST_METHOD'] != 'GET'
+      return [422, {'X-DynDNS-Response' => 'not_found'}, []] if env['PATH_INFO'] != '/nic/update'
 
       handle_dyndns_request(env)
     end
 
     def self.run!
       if ARGV.length != 1
-        puts "Usage: dyndnsd config_file"
+        puts 'Usage: dyndnsd config_file'
         exit 1
       end
 
       config_file = ARGV[0]
 
-      if not File.file?(config_file)
-        puts "Config file not found!"
+      if !File.file?(config_file)
+        puts 'Config file not found!'
         exit 1
       end
 
       puts "DynDNSd version #{Dyndnsd::VERSION}"
       puts "Using config file #{config_file}"
 
-      config = YAML::load(File.open(config_file, 'r') { |f| f.read })
+      config = YAML.safe_load(File.open(config_file, 'r', &:read))
 
       setup_logger(config)
 
-      Dyndnsd.logger.info "Starting..."
+      Dyndnsd.logger.info 'Starting...'
 
       # drop priviliges as soon as possible
       # NOTE: first change group than user
       Process::Sys.setgid(Etc.getgrnam(config['group']).gid) if config['group']
       Process::Sys.setuid(Etc.getpwnam(config['user']).uid) if config['user']
 
-      setup_traps()
+      setup_traps
 
       setup_monitoring(config)
 
@@ -97,12 +100,12 @@ module Dyndnsd
 
     private
 
-    def extract_v4_and_v6_address(env, params)
-      return [] if not params["myip"]
+    def extract_v4_and_v6_address(params)
+      return [] if !(params['myip'])
       begin
-        IPAddr.new(params["myip"], Socket::AF_INET)
-        IPAddr.new(params["myip6"], Socket::AF_INET6)
-        [params["myip"], params["myip6"]]
+        IPAddr.new(params['myip'], Socket::AF_INET)
+        IPAddr.new(params['myip6'], Socket::AF_INET6)
+        [params['myip'], params['myip6']]
       rescue ArgumentError
         []
       end
@@ -110,23 +113,23 @@ module Dyndnsd
 
     def extract_myips(env, params)
       # require presence of myip parameter as valid IPAddr (v4) and valid myip6
-      return extract_v4_and_v6_address(env, params) if params.has_key?("myip6")
+      return extract_v4_and_v6_address(params) if params.key?('myip6')
 
       # check whether myip parameter has valid IPAddr
-      return [params["myip"]] if params.has_key?("myip") and Helper.is_ip_valid?(params["myip"])
+      return [params['myip']] if params.key?('myip') && Helper.ip_valid?(params['myip'])
 
       # check whether X-Real-IP header has valid IPAddr
-      return [env["HTTP_X_REAL_IP"]] if env.has_key?("HTTP_X_REAL_IP") and Helper.is_ip_valid?(env["HTTP_X_REAL_IP"])
+      return [env['HTTP_X_REAL_IP']] if env.key?('HTTP_X_REAL_IP') && Helper.ip_valid?(env['HTTP_X_REAL_IP'])
 
       # fallback value, always present
-      [env["REMOTE_ADDR"]]
+      [env['REMOTE_ADDR']]
     end
 
     def process_changes(hostnames, myips)
       changes = []
       hostnames.each do |hostname|
         # myips order is always deterministic
-        if (not @db['hosts'].include? hostname) or (@db['hosts'][hostname] != myips)
+        if (!@db['hosts'].include? hostname) || (@db['hosts'][hostname] != myips)
           @db['hosts'][hostname] = myips
           changes << :good
           Metriks.meter('requests.good').mark
@@ -138,7 +141,7 @@ module Dyndnsd
       changes
     end
 
-    def update_db()
+    def update_db
       @db['serial'] += 1
       Dyndnsd.logger.info "Committing update ##{@db['serial']}"
       @db.save
@@ -147,18 +150,18 @@ module Dyndnsd
     end
 
     def handle_dyndns_request(env)
-      params = Rack::Utils.parse_query(env["QUERY_STRING"])
+      params = Rack::Utils.parse_query(env['QUERY_STRING'])
 
       # require hostname parameter
-      return [422, {'X-DynDNS-Response' => 'hostname_missing'}, []] if not params["hostname"]
+      return [422, {'X-DynDNS-Response' => 'hostname_missing'}, []] if !(params['hostname'])
 
-      hostnames = params["hostname"].split(',')
+      hostnames = params['hostname'].split(',')
 
       # check for invalid hostnames
-      invalid_hostnames = hostnames.select { |hostname| not Helper.is_fqdn_valid?(hostname, @domain) }
+      invalid_hostnames = hostnames.select { |hostname| !Helper.fqdn_valid?(hostname, @domain) }
       return [422, {'X-DynDNS-Response' => 'hostname_malformed'}, []] if invalid_hostnames.any?
 
-      user = env["REMOTE_USER"]
+      user = env['REMOTE_USER']
 
       # check for hostnames that the user does not own
       forbidden_hostnames = hostnames - @users[user]['hosts']
@@ -181,29 +184,29 @@ module Dyndnsd
 
     # SETUP
 
-    def self.setup_logger(config)
+    private_class_method def self.setup_logger(config)
       if config['logfile']
         Dyndnsd.logger = Logger.new(config['logfile'])
       else
         Dyndnsd.logger = Logger.new(STDOUT)
       end
 
-      Dyndnsd.logger.progname = "dyndnsd"
+      Dyndnsd.logger.progname = 'dyndnsd'
       Dyndnsd.logger.formatter = LogFormatter.new
     end
 
-    def self.setup_traps()
+    private_class_method def self.setup_traps
       Signal.trap('INT') do
-        Dyndnsd.logger.info "Quitting..."
+        Dyndnsd.logger.info 'Quitting...'
         Rack::Handler::WEBrick.shutdown
       end
       Signal.trap('TERM') do
-        Dyndnsd.logger.info "Quitting..."
+        Dyndnsd.logger.info 'Quitting...'
         Rack::Handler::WEBrick.shutdown
       end
     end
 
-    def self.setup_monitoring(config)
+    private_class_method def self.setup_monitoring(config)
       # configure metriks
       if config['graphite']
         host = config['graphite']['host'] || 'localhost'
@@ -224,14 +227,14 @@ module Dyndnsd
       end
     end
 
-    def self.setup_rack(config)
+    private_class_method def self.setup_rack(config)
       # configure daemon
       db = Database.new(config['db'])
       updater = Updater::CommandWithBindZone.new(config['domain'], config['updater']['params']) if config['updater']['name'] == 'command_with_bind_zone'
       daemon = Daemon.new(config, db, updater)
 
       # configure rack
-      app = Rack::Auth::Basic.new(daemon, "DynDNS", &daemon.method(:is_authorized?))
+      app = Rack::Auth::Basic.new(daemon, 'DynDNS', &daemon.method(:authorized?))
 
       if config['responder'] == 'RestStyle'
         app = Responder::RestStyle.new(app)
@@ -239,7 +242,7 @@ module Dyndnsd
         app = Responder::DynDNSStyle.new(app)
       end
 
-      Rack::Handler::WEBrick.run app, :Host => config['host'], :Port => config['port']
+      Rack::Handler::WEBrick.run app, Host: config['host'], Port: config['port']
     end
   end
 end
diff --git a/lib/dyndnsd/database.rb b/lib/dyndnsd/database.rb
index e5fa710..eb88106 100644
--- a/lib/dyndnsd/database.rb
+++ b/lib/dyndnsd/database.rb
@@ -4,27 +4,27 @@ require 'forwardable'
 module Dyndnsd
   class Database
     extend Forwardable
-    
+
     def_delegators :@db, :[], :[]=, :each, :has_key?
-  
+
     def initialize(db_file)
       @db_file = db_file
     end
-    
+
     def load
       if File.file?(@db_file)
-        @db = JSON.load(File.open(@db_file, 'r') { |f| f.read })
+        @db = JSON.parse(File.open(@db_file, 'r', &:read))
       else
         @db = {}
       end
       @db_hash = @db.hash
     end
-    
+
     def save
       File.open(@db_file, 'w') { |f| JSON.dump(@db, f) }
       @db_hash = @db.hash
     end
-    
+
     def changed?
       @db_hash != @db.hash
     end
diff --git a/lib/dyndnsd/generator/bind.rb b/lib/dyndnsd/generator/bind.rb
index 550f978..66e2368 100644
--- a/lib/dyndnsd/generator/bind.rb
+++ b/lib/dyndnsd/generator/bind.rb
@@ -14,21 +14,21 @@ module Dyndnsd
         out = []
         out << "$TTL #{@ttl}"
         out << "$ORIGIN #{@domain}."
-        out << ""
+        out << ''
         out << "@ IN SOA #{@dns} #{@email_addr} ( #{zone['serial']} 3h 5m 1w 1h )"
         out << "@ IN NS #{@dns}"
-        out << ""
-        zone['hosts'].each do |hostname,ips|
+        out << ''
+        zone['hosts'].each do |hostname, ips|
           ips.each do |ip|
             ip = IPAddr.new(ip).native
-            type = ip.ipv6? ? "AAAA" : "A"
+            type = ip.ipv6? ? 'AAAA' : 'A'
             name = hostname.chomp('.' + @domain)
             out << "#{name} IN #{type} #{ip}"
           end
         end
-        out << ""
+        out << ''
         out << @additional_zone_content
-        out << ""
+        out << ''
         out.join("\n")
       end
     end
diff --git a/lib/dyndnsd/helper.rb b/lib/dyndnsd/helper.rb
index 14ca66a..74de88e 100644
--- a/lib/dyndnsd/helper.rb
+++ b/lib/dyndnsd/helper.rb
@@ -3,21 +3,19 @@ require 'ipaddr'
 
 module Dyndnsd
   class Helper
-    def self.is_fqdn_valid?(hostname, domain)
+    def self.fqdn_valid?(hostname, domain)
       return false if hostname.length < domain.length + 2
-      return false if not hostname.end_with?(domain)
+      return false if !hostname.end_with?(domain)
       name = hostname.chomp(domain)
-      return false if not name.match(/^[a-zA-Z0-9_-]+\.$/)
+      return false if !name.match(/^[a-zA-Z0-9_-]+\.$/)
       true
     end
 
-    def self.is_ip_valid?(ip)
-      begin
-        IPAddr.new(ip)
-        return true
-      rescue ArgumentError
-        return false
-      end
+    def self.ip_valid?(ip)
+      IPAddr.new(ip)
+      return true
+    rescue ArgumentError
+      return false
     end
   end
 end
diff --git a/lib/dyndnsd/responder/dyndns_style.rb b/lib/dyndnsd/responder/dyndns_style.rb
index f046256..51f829a 100644
--- a/lib/dyndnsd/responder/dyndns_style.rb
+++ b/lib/dyndnsd/responder/dyndns_style.rb
@@ -8,7 +8,7 @@ module Dyndnsd
 
       def call(env)
         @app.call(env).tap do |status_code, headers, body|
-          if headers.has_key?("X-DynDNS-Response")
+          if headers.key?('X-DynDNS-Response')
             return decorate_dyndnsd_response(status_code, headers, body)
           else
             return decorate_other_response(status_code, headers, body)
@@ -20,17 +20,17 @@ module Dyndnsd
 
       def decorate_dyndnsd_response(status_code, headers, body)
         if status_code == 200
-          [200, {"Content-Type" => "text/plain"}, [get_success_body(body[0], body[1])]]
+          [200, {'Content-Type' => 'text/plain'}, [get_success_body(body[0], body[1])]]
         elsif status_code == 422
-          get_error_response_map[headers["X-DynDNS-Response"]]
+          error_response_map[headers['X-DynDNS-Response']]
         end
       end
 
-      def decorate_other_response(status_code, headers, body)
+      def decorate_other_response(status_code, headers, _body)
         if status_code == 400
-          [status_code, headers, ["Bad Request"]]
+          [status_code, headers, ['Bad Request']]
         elsif status_code == 401
-          [status_code, headers, ["badauth"]]
+          [status_code, headers, ['badauth']]
         end
       end
 
@@ -38,15 +38,15 @@ module Dyndnsd
         changes.map { |change| "#{change} #{myips.join(' ')}" }.join("\n")
       end
 
-      def get_error_response_map
+      def error_response_map
         {
           # general http errors
-          'method_forbidden'   => [405, {"Content-Type" => "text/plain"}, ["Method Not Allowed"]],
-          'not_found'          => [404, {"Content-Type" => "text/plain"}, ["Not Found"]],
+          'method_forbidden'   => [405, {'Content-Type' => 'text/plain'}, ['Method Not Allowed']],
+          'not_found'          => [404, {'Content-Type' => 'text/plain'}, ['Not Found']],
           # specific errors
-          'hostname_missing'   => [200, {"Content-Type" => "text/plain"}, ["notfqdn"]],
-          'hostname_malformed' => [200, {"Content-Type" => "text/plain"}, ["notfqdn"]],
-          'host_forbidden'     => [200, {"Content-Type" => "text/plain"}, ["nohost"]]
+          'hostname_missing'   => [200, {'Content-Type' => 'text/plain'}, ['notfqdn']],
+          'hostname_malformed' => [200, {'Content-Type' => 'text/plain'}, ['notfqdn']],
+          'host_forbidden'     => [200, {'Content-Type' => 'text/plain'}, ['nohost']]
         }
       end
     end
diff --git a/lib/dyndnsd/responder/rest_style.rb b/lib/dyndnsd/responder/rest_style.rb
index a52d221..e2e0b8d 100644
--- a/lib/dyndnsd/responder/rest_style.rb
+++ b/lib/dyndnsd/responder/rest_style.rb
@@ -8,7 +8,7 @@ module Dyndnsd
 
       def call(env)
         @app.call(env).tap do |status_code, headers, body|
-          if headers.has_key?("X-DynDNS-Response")
+          if headers.key?('X-DynDNS-Response')
             return decorate_dyndnsd_response(status_code, headers, body)
           else
             return decorate_other_response(status_code, headers, body)
@@ -20,17 +20,17 @@ module Dyndnsd
 
       def decorate_dyndnsd_response(status_code, headers, body)
         if status_code == 200
-          [200, {"Content-Type" => "text/plain"}, [get_success_body(body[0], body[1])]]
+          [200, {'Content-Type' => 'text/plain'}, [get_success_body(body[0], body[1])]]
         elsif status_code == 422
-          get_error_response_map[headers["X-DynDNS-Response"]]
+          error_response_map[headers['X-DynDNS-Response']]
         end
       end
 
-      def decorate_other_response(status_code, headers, body)
+      def decorate_other_response(status_code, headers, _body)
         if status_code == 400
-          [status_code, headers, ["Bad Request"]]
+          [status_code, headers, ['Bad Request']]
         elsif status_code == 401
-          [status_code, headers, ["Unauthorized"]]
+          [status_code, headers, ['Unauthorized']]
         end
       end
 
@@ -38,15 +38,15 @@ module Dyndnsd
         changes.map { |change| change == :good ? "Changed to #{myips.join(' ')}" : "No change needed for #{myips.join(' ')}" }.join("\n")
       end
 
-      def get_error_response_map
+      def error_response_map
         {
           # general http errors
-          'method_forbidden'   => [405, {"Content-Type" => "text/plain"}, ["Method Not Allowed"]],
-          'not_found'          => [404, {"Content-Type" => "text/plain"}, ["Not Found"]],
+          'method_forbidden'   => [405, {'Content-Type' => 'text/plain'}, ['Method Not Allowed']],
+          'not_found'          => [404, {'Content-Type' => 'text/plain'}, ['Not Found']],
           # specific errors
-          'hostname_missing'   => [422, {"Content-Type" => "text/plain"}, ["Hostname missing"]],
-          'hostname_malformed' => [422, {"Content-Type" => "text/plain"}, ["Hostname malformed"]],
-          'host_forbidden'     => [403, {"Content-Type" => "text/plain"}, ["Forbidden"]]
+          'hostname_missing'   => [422, {'Content-Type' => 'text/plain'}, ['Hostname missing']],
+          'hostname_malformed' => [422, {'Content-Type' => 'text/plain'}, ['Hostname malformed']],
+          'host_forbidden'     => [403, {'Content-Type' => 'text/plain'}, ['Forbidden']]
         }
       end
     end
diff --git a/lib/dyndnsd/updater/command_with_bind_zone.rb b/lib/dyndnsd/updater/command_with_bind_zone.rb
index 6f05374..a7d1aae 100644
--- a/lib/dyndnsd/updater/command_with_bind_zone.rb
+++ b/lib/dyndnsd/updater/command_with_bind_zone.rb
@@ -7,7 +7,7 @@ module Dyndnsd
         @command = config['command']
         @generator = Generator::Bind.new(domain, config)
       end
-      
+
       def update(zone)
         # write zone file in bind syntax
         File.open(@zone_file, 'w') { |f| f.write(@generator.generate(zone)) }
diff --git a/lib/dyndnsd/version.rb b/lib/dyndnsd/version.rb
index c395a0b..ae0f23b 100644
--- a/lib/dyndnsd/version.rb
+++ b/lib/dyndnsd/version.rb
@@ -1,4 +1,4 @@
 
 module Dyndnsd
-  VERSION = "1.6.1"
+  VERSION = '1.6.1'.freeze
 end
diff --git a/spec/daemon_spec.rb b/spec/daemon_spec.rb
index a24f24f..2fcbc7e 100644
--- a/spec/daemon_spec.rb
+++ b/spec/daemon_spec.rb
@@ -20,9 +20,9 @@ describe Dyndnsd::Daemon do
     updater = Dyndnsd::Updater::Dummy.new
     daemon = Dyndnsd::Daemon.new(config, db, updater)
 
-    app = Rack::Auth::Basic.new(daemon, "DynDNS", &daemon.method(:is_authorized?))
+    app = Rack::Auth::Basic.new(daemon, 'DynDNS', &daemon.method(:authorized?))
 
-    app = Dyndnsd::Responder::DynDNSStyle.new(app)
+    Dyndnsd::Responder::DynDNSStyle.new(app)
   end
 
   it 'requires authentication' do
@@ -189,7 +189,7 @@ describe Dyndnsd::Daemon do
 
     get '/nic/update?hostname=foo.example.org&myip=1.2.3.4&myip6=2001:db8::1'
     expect(last_response).to be_ok
-    expect(last_response.body).to eq("good 1.2.3.4 2001:db8::1")
+    expect(last_response.body).to eq('good 1.2.3.4 2001:db8::1')
 
     get '/nic/update?hostname=foo.example.org&myip=BROKENIP&myip6=2001:db8::1'
     expect(last_response).to be_ok
diff --git a/spec/support/dummy_database.rb b/spec/support/dummy_database.rb
index 82c530f..b67a96d 100644
--- a/spec/support/dummy_database.rb
+++ b/spec/support/dummy_database.rb
@@ -4,7 +4,7 @@ require 'forwardable'
 module Dyndnsd
   class DummyDatabase
     extend Forwardable
-  
+
     def_delegators :@db, :[], :[]=, :each, :has_key?
 
     def initialize(db_init)
@@ -25,5 +25,3 @@ module Dyndnsd
     end
   end
 end
-
-