diff --git a/lib/rubygems/config_file.rb b/lib/rubygems/config_file.rb
index 4aa8b4d..8354c08 100644
--- a/lib/rubygems/config_file.rb
+++ b/lib/rubygems/config_file.rb
@@ -62,12 +62,7 @@ class Gem::ConfigFile
   # :stopdoc:

   SYSTEM_CONFIG_PATH =
-    begin
-      require "etc"
-      Etc.sysconfdir
-    rescue LoadError, NoMethodError
-      RbConfig::CONFIG["sysconfdir"] || "/etc"
-    end
+    RbConfig::CONFIG["sysconfdir"] || "/etc"

   # :startdoc:

diff --git a/lib/rubygems/defaults.rb b/lib/rubygems/defaults.rb
index b186375..de168c4 100644
--- a/lib/rubygems/defaults.rb
+++ b/lib/rubygems/defaults.rb
@@ -20,13 +20,7 @@ def self.default_sources
   # specified in the environment

   def self.default_spec_cache_dir
-    default_spec_cache_dir = File.join Gem.user_home, ".gem", "specs"
-
-    unless File.exist?(default_spec_cache_dir)
-      default_spec_cache_dir = File.join Gem.data_home, "gem", "specs"
-    end
-
-    default_spec_cache_dir
+    File.join Gem.data_home, "specs"
   end

   ##
@@ -34,7 +28,7 @@ def self.default_spec_cache_dir
   # specified in the environment

   def self.default_dir
-    @default_dir ||= File.join(RbConfig::CONFIG["rubylibprefix"], "gems", RbConfig::CONFIG["ruby_version"])
+    @default_dir ||= File.join(RbConfig::CONFIG["rubylibprefix"], "gems", RbConfig::CONFIG["ruby_version"])
   end

   ##
@@ -100,8 +94,7 @@ def self.user_home
   # Path for gems in the user's home directory

   def self.user_dir
-    gem_dir = File.join(Gem.user_home, ".gem")
-    gem_dir = File.join(Gem.data_home, "gem") unless File.exist?(gem_dir)
+    gem_dir = Gem.data_home
     parts = [gem_dir, ruby_engine]
     parts << RbConfig::CONFIG["ruby_version"] unless RbConfig::CONFIG["ruby_version"].empty?
     File.join parts
@@ -111,18 +104,17 @@ def self.user_dir
   # The path to standard location of the user's configuration directory.

   def self.config_home
-    @config_home ||= (ENV["XDG_CONFIG_HOME"] || File.join(Gem.user_home, ".config"))
+    @config_home ||= (ENV["XDG_CONFIG_HOME"] || File.join(Gem.user_home, ".gem"))
   end

   ##
   # Finds the user's config file

   def self.find_config_file
-    gemrc = File.join Gem.user_home, ".gemrc"
-    if File.exist? gemrc
-      gemrc
+    @gemrc = if ENV["XDG_CONFIG_HOME"]
+      File.join ENV["XDG_CONFIG_HOME"], "gemrc"
     else
-      File.join Gem.config_home, "gem", "gemrc"
+      File.join Gem.user_home, ".gemrc"
     end
   end

@@ -137,7 +129,7 @@ def self.config_file
   # The path to standard location of the user's state file.

   def self.state_file
-    @state_file ||= File.join(Gem.state_home, "gem", "last_update_check").tap(&Gem::UNTAINT)
+    @state_file ||= File.join(Gem.state_home, "last_update_check").tap(&Gem::UNTAINT)
   end

   ##
@@ -151,7 +143,11 @@ def self.cache_home
   # The path to standard location of the user's data directory.

   def self.data_home
-    @data_home ||= (ENV["XDG_DATA_HOME"] || File.join(Gem.user_home, ".local", "share"))
+    @data_home ||= if ENV["XDG_DATA_HOME"]
+      File.join(ENV["XDG_DATA_HOME"], "gem")
+    else
+      File.join(Gem.user_home, ".gem")
+    end
   end

   ##
@@ -176,6 +172,7 @@ def self.default_path
     path << user_dir if user_home && File.exist?(user_home)
     path << default_dir
     path << vendor_dir if vendor_dir && File.directory?(vendor_dir)
+    path << File.expand_path(File.join(__FILE__, "../../../../../ruby-lang.org", "v#{RbConfig::CONFIG["RUBY_PROGRAM_VERSION"]}", "lib/ruby/gems", RbConfig::CONFIG["ruby_version"]))
     path
   end

@@ -197,7 +194,7 @@ def self.default_exec_format
   # The default directory for binaries

   def self.default_bindir
-    RbConfig::CONFIG["bindir"]
+    "/usr/local/bin"
   end

   def self.ruby_engine
@@ -208,26 +205,14 @@ def self.ruby_engine
   # The default signing key path

   def self.default_key_path
-    default_key_path = File.join Gem.user_home, ".gem", "gem-private_key.pem"
-
-    unless File.exist?(default_key_path)
-      default_key_path = File.join Gem.data_home, "gem", "gem-private_key.pem"
-    end
-
-    default_key_path
+    File.join Gem.data_home, "private-key.pem"
   end

   ##
   # The default signing certificate chain path

   def self.default_cert_path
-    default_cert_path = File.join Gem.user_home, ".gem", "gem-public_cert.pem"
-
-    unless File.exist?(default_cert_path)
-      default_cert_path = File.join Gem.data_home, "gem", "gem-public_cert.pem"
-    end
-
-    default_cert_path
+    File.join Gem.data_home, "public-cert.pem"
   end

   ##
@@ -267,7 +252,10 @@ def self.vendor_dir # :nodoc:
   # end

   def self.operating_system_defaults
-    {}
+    {
+      'install' => '--no-rdoc --no-ri --env-shebang',
+      'update' => '--no-rdoc --no-ri --env-shebang'
+    }
   end

   ##
diff --git a/lib/rubygems/installer.rb b/lib/rubygems/installer.rb
index 8fef455..3ef4e30 100644
--- a/lib/rubygems/installer.rb
+++ b/lib/rubygems/installer.rb
@@ -188,9 +188,9 @@ def initialize(package, options={})
     @package.prog_mode = options[:prog_mode]
     @package.data_mode = options[:data_mode]

-    if options[:user_install]
+    if options[:user_install] or options[:user_install].nil? and not File.writable? Gem.paths.home
       @gem_home = Gem.user_dir
-      @bin_dir = Gem.bindir gem_home unless options[:bin_dir]
+      @bin_dir = File.join(Gem.user_home, ".local/bin") unless options[:bin_dir]
       @plugins_dir = Gem.plugindir(gem_home)
       check_that_user_bin_dir_is_in_path
     end