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-rw-r--r--doc/manual/command-ref/conf-file.xml27
-rw-r--r--doc/manual/expressions/advanced-attributes.xml14
-rw-r--r--doc/manual/expressions/builtins.xml364
-rw-r--r--doc/manual/packages/s3-substituter.xml202
-rw-r--r--doc/manual/release-notes/release-notes.xml1
-rw-r--r--doc/manual/release-notes/rl-2.2.xml25
-rw-r--r--scripts/nix-profile-daemon.sh.in2
-rw-r--r--src/libstore/build.cc210
-rw-r--r--src/libstore/derivations.cc14
-rw-r--r--src/libstore/derivations.hh4
-rw-r--r--src/libstore/download.cc45
-rw-r--r--src/libstore/globals.cc15
-rw-r--r--src/libstore/globals.hh6
-rw-r--r--src/libstore/parsed-derivations.cc111
-rw-r--r--src/libstore/parsed-derivations.hh35
-rw-r--r--src/libstore/s3-binary-cache-store.cc28
-rw-r--r--src/libstore/store-api.cc2
-rw-r--r--src/libutil/serialise.cc26
-rwxr-xr-xsrc/nix-build/nix-build.cc8
-rw-r--r--src/nix-daemon/nix-daemon.cc2
-rw-r--r--src/nix/copy.cc8
-rw-r--r--src/nix/verify.cc2
-rw-r--r--tests/build-remote.sh3
-rw-r--r--tests/signing.sh4
24 files changed, 714 insertions, 444 deletions
diff --git a/doc/manual/command-ref/conf-file.xml b/doc/manual/command-ref/conf-file.xml
index fd09883be402..e9947ebc673f 100644
--- a/doc/manual/command-ref/conf-file.xml
+++ b/doc/manual/command-ref/conf-file.xml
@@ -757,6 +757,33 @@ password <replaceable>my-password</replaceable>
   </varlistentry>
 
 
+  <varlistentry xml:id="conf-system-features"><term><literal>system-features</literal></term>
+
+    <listitem><para>A set of system “features” supported by this
+    machine, e.g. <literal>kvm</literal>. Derivations can express a
+    dependency on such features through the derivation attribute
+    <varname>requiredSystemFeatures</varname>. For example, the
+    attribute
+
+<programlisting>
+requiredSystemFeatures = [ "kvm" ];
+</programlisting>
+
+    ensures that the derivation can only be built on a machine with
+    the <literal>kvm</literal> feature.</para>
+
+    <para>This setting by default includes <literal>kvm</literal> if
+    <filename>/dev/kvm</filename> is accessible, and the
+    pseudo-features <literal>nixos-test</literal>,
+    <literal>benchmark</literal> and <literal>big-parallel</literal>
+    that are used in Nixpkgs to route builds to specific
+    machines.</para>
+
+    </listitem>
+
+  </varlistentry>
+
+
   <varlistentry xml:id="conf-timeout"><term><literal>timeout</literal></term>
 
     <listitem>
diff --git a/doc/manual/expressions/advanced-attributes.xml b/doc/manual/expressions/advanced-attributes.xml
index 9422e82ff362..2af7a51acfbb 100644
--- a/doc/manual/expressions/advanced-attributes.xml
+++ b/doc/manual/expressions/advanced-attributes.xml
@@ -216,7 +216,7 @@ fetchurl {
 <programlisting>
 { stdenv, curl }: # The <command>curl</command> program is used for downloading.
 
-{ url, md5 }:
+{ url, sha256 }:
 
 stdenv.mkDerivation {
   name = baseNameOf (toString url);
@@ -224,10 +224,10 @@ stdenv.mkDerivation {
   buildInputs = [ curl ];
 
   # This is a fixed-output derivation; the output must be a regular
-  # file with MD5 hash <varname>md5</varname>.
+  # file with SHA256 hash <varname>sha256</varname>.
   outputHashMode = "flat";
-  outputHashAlgo = "md5";
-  outputHash = md5;
+  outputHashAlgo = "sha256";
+  outputHash = sha256;
 
   inherit url;
 }
@@ -237,8 +237,8 @@ stdenv.mkDerivation {
 
     <para>The <varname>outputHashAlgo</varname> attribute specifies
     the hash algorithm used to compute the hash.  It can currently be
-    <literal>"md5"</literal>, <literal>"sha1"</literal> or
-    <literal>"sha256"</literal>.</para>
+    <literal>"sha1"</literal>, <literal>"sha256"</literal> or
+    <literal>"sha512"</literal>.</para>
 
     <para>The <varname>outputHashMode</varname> attribute determines
     how the hash is computed.  It must be one of the following two
@@ -251,7 +251,7 @@ stdenv.mkDerivation {
         <listitem><para>The output must be a non-executable regular
         file.  If it isn’t, the build fails.  The hash is simply
         computed over the contents of that file (so it’s equal to what
-        Unix commands like <command>md5sum</command> or
+        Unix commands like <command>sha256sum</command> or
         <command>sha1sum</command> produce).</para>
 
         <para>This is the default.</para></listitem>
diff --git a/doc/manual/expressions/builtins.xml b/doc/manual/expressions/builtins.xml
index 873f30b062ee..8d12da9b1356 100644
--- a/doc/manual/expressions/builtins.xml
+++ b/doc/manual/expressions/builtins.xml
@@ -21,7 +21,8 @@ available as <function>builtins.derivation</function>.</para>
 <variablelist>
 
 
-  <varlistentry><term><function>abort</function> <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-abort'>
+    <term><function>abort</function> <replaceable>s</replaceable></term>
 
     <listitem><para>Abort Nix expression evaluation, print error
     message <replaceable>s</replaceable>.</para></listitem>
@@ -29,8 +30,10 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.add</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-add'>
+    <term><function>builtins.add</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable>
+    </term>
 
     <listitem><para>Return the sum of the numbers
     <replaceable>e1</replaceable> and
@@ -39,8 +42,9 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.all</function>
-  <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-all'>
+    <term><function>builtins.all</function>
+    <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if the function
     <replaceable>pred</replaceable> returns <literal>true</literal>
@@ -50,8 +54,9 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.any</function>
-  <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-any'>
+    <term><function>builtins.any</function>
+    <replaceable>pred</replaceable> <replaceable>list</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if the function
     <replaceable>pred</replaceable> returns <literal>true</literal>
@@ -61,8 +66,9 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.attrNames</function>
-  <replaceable>set</replaceable></term>
+  <varlistentry xml:id='builtin-attrNames'>
+    <term><function>builtins.attrNames</function>
+    <replaceable>set</replaceable></term>
 
     <listitem><para>Return the names of the attributes in the set
     <replaceable>set</replaceable> in an alphabetically sorted list.  For instance,
@@ -72,8 +78,9 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.attrValues</function>
-  <replaceable>set</replaceable></term>
+  <varlistentry xml:id='builtin-attrValues'>
+    <term><function>builtins.attrValues</function>
+    <replaceable>set</replaceable></term>
 
     <listitem><para>Return the values of the attributes in the set
     <replaceable>set</replaceable> in the order corresponding to the
@@ -82,7 +89,8 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>baseNameOf</function> <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-baseNameOf'>
+    <term><function>baseNameOf</function> <replaceable>s</replaceable></term>
 
     <listitem><para>Return the <emphasis>base name</emphasis> of the
     string <replaceable>s</replaceable>, that is, everything following
@@ -92,8 +100,9 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.bitAnd</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-bitAnd'>
+    <term><function>builtins.bitAnd</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return the bitwise AND of the integers
     <replaceable>e1</replaceable> and
@@ -102,8 +111,9 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.bitOr</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-bitOr'>
+    <term><function>builtins.bitOr</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return the bitwise OR of the integers
     <replaceable>e1</replaceable> and
@@ -112,8 +122,9 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.bitXor</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-bitXor'>
+    <term><function>builtins.bitXor</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return the bitwise XOR of the integers
     <replaceable>e1</replaceable> and
@@ -122,7 +133,8 @@ available as <function>builtins.derivation</function>.</para>
   </varlistentry>
 
 
-  <varlistentry><term><varname>builtins</varname></term>
+  <varlistentry xml:id='builtin-builtins'>
+    <term><varname>builtins</varname></term>
 
     <listitem><para>The set <varname>builtins</varname> contains all
     the built-in functions and values.  You can use
@@ -139,8 +151,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.compareVersions</function>
-  <replaceable>s1</replaceable> <replaceable>s2</replaceable></term>
+  <varlistentry xml:id='builtin-compareVersions'>
+    <term><function>builtins.compareVersions</function>
+    <replaceable>s1</replaceable> <replaceable>s2</replaceable></term>
 
     <listitem><para>Compare two strings representing versions and
     return <literal>-1</literal> if version
@@ -156,8 +169,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.splitVersion</function>
-  <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-splitVersion'>
+    <term><function>builtins.splitVersion</function>
+    <replaceable>s</replaceable></term>
 
     <listitem><para>Split a string representing a version into its
     components, by the same version splitting logic underlying the
@@ -167,16 +181,18 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.concatLists</function>
-  <replaceable>lists</replaceable></term>
+  <varlistentry xml:id='builtin-concatLists'>
+    <term><function>builtins.concatLists</function>
+    <replaceable>lists</replaceable></term>
 
     <listitem><para>Concatenate a list of lists into a single
     list.</para></listitem>
 
   </varlistentry>
 
-  <varlistentry><term><function>builtins.concatStringsSep</function>
-  <replaceable>separator</replaceable> <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-concatStringsSep'>
+    <term><function>builtins.concatStringsSep</function>
+    <replaceable>separator</replaceable> <replaceable>list</replaceable></term>
 
     <listitem><para>Concatenate a list of strings with a separator
     between each element, e.g. <literal>concatStringsSep "/"
@@ -184,8 +200,8 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
 
   </varlistentry>
 
-  <varlistentry
-  xml:id='builtin-currentSystem'><term><varname>builtins.currentSystem</varname></term>
+  <varlistentry xml:id='builtin-currentSystem'>
+    <term><varname>builtins.currentSystem</varname></term>
 
     <listitem><para>The built-in value <varname>currentSystem</varname>
     evaluates to the Nix platform identifier for the Nix installation
@@ -218,8 +234,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   -->
 
 
-  <varlistentry><term><function>builtins.deepSeq</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-deepSeq'>
+    <term><function>builtins.deepSeq</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>This is like <literal>seq
     <replaceable>e1</replaceable>
@@ -231,8 +248,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>derivation</function>
-  <replaceable>attrs</replaceable></term>
+  <varlistentry xml:id='builtin-derivation'>
+    <term><function>derivation</function>
+    <replaceable>attrs</replaceable></term>
 
     <listitem><para><function>derivation</function> is described in
     <xref linkend='ssec-derivation' />.</para></listitem>
@@ -240,7 +258,8 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>dirOf</function> <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-dirOf'>
+    <term><function>dirOf</function> <replaceable>s</replaceable></term>
 
     <listitem><para>Return the directory part of the string
     <replaceable>s</replaceable>, that is, everything before the final
@@ -250,8 +269,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.div</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-div'>
+    <term><function>builtins.div</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return the quotient of the numbers
     <replaceable>e1</replaceable> and
@@ -259,8 +279,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
 
   </varlistentry>
 
-  <varlistentry><term><function>builtins.elem</function>
-  <replaceable>x</replaceable> <replaceable>xs</replaceable></term>
+  <varlistentry xml:id='builtin-elem'>
+    <term><function>builtins.elem</function>
+    <replaceable>x</replaceable> <replaceable>xs</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if a value equal to
     <replaceable>x</replaceable> occurs in the list
@@ -270,8 +291,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.elemAt</function>
-  <replaceable>xs</replaceable> <replaceable>n</replaceable></term>
+  <varlistentry xml:id='builtin-elemAt'>
+    <term><function>builtins.elemAt</function>
+    <replaceable>xs</replaceable> <replaceable>n</replaceable></term>
 
     <listitem><para>Return element <replaceable>n</replaceable> from
     the list <replaceable>xs</replaceable>.  Elements are counted
@@ -281,8 +303,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.fetchurl</function>
-  <replaceable>url</replaceable></term>
+  <varlistentry xml:id='builtin-fetchurl'>
+    <term><function>builtins.fetchurl</function>
+    <replaceable>url</replaceable></term>
 
     <listitem><para>Download the specified URL and return the path of
     the downloaded file. This function is not available if <link
@@ -292,8 +315,9 @@ if builtins ? getEnv then builtins.getEnv "PATH" else ""</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>fetchTarball</function>
-  <replaceable>url</replaceable></term>
+  <varlistentry xml:id='builtin-fetchTarball'>
+    <term><function>fetchTarball</function>
+    <replaceable>url</replaceable></term>
 
     <listitem><para>Download the specified URL, unpack it and return
     the path of the unpacked tree. The file must be a tape archive
@@ -346,7 +370,7 @@ stdenv.mkDerivation { … }
 
   </varlistentry>
 
-  <varlistentry>
+  <varlistentry xml:id='builtin-fetchGit'>
     <term>
       <function>builtins.fetchGit</function>
       <replaceable>args</replaceable>
@@ -546,7 +570,8 @@ stdenv.mkDerivation {
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.foldl’</function>
+  <varlistentry xml:id='builtin-foldl-prime'>
+    <term><function>builtins.foldl’</function>
     <replaceable>op</replaceable> <replaceable>nul</replaceable> <replaceable>list</replaceable></term>
 
     <listitem><para>Reduce a list by applying a binary operator, from
@@ -559,7 +584,8 @@ stdenv.mkDerivation {
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.functionArgs</function>
+  <varlistentry xml:id='builtin-functionArgs'>
+    <term><function>builtins.functionArgs</function>
     <replaceable>f</replaceable></term>
 
     <listitem><para>
@@ -577,7 +603,8 @@ stdenv.mkDerivation {
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.fromJSON</function> <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-fromJSON'>
+    <term><function>builtins.fromJSON</function> <replaceable>e</replaceable></term>
 
     <listitem><para>Convert a JSON string to a Nix
     value. For example,
@@ -592,8 +619,9 @@ builtins.fromJSON ''{"x": [1, 2, 3], "y": null}''
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.genList</function>
-  <replaceable>generator</replaceable> <replaceable>length</replaceable></term>
+  <varlistentry xml:id='builtin-genList'>
+    <term><function>builtins.genList</function>
+    <replaceable>generator</replaceable> <replaceable>length</replaceable></term>
 
     <listitem><para>Generate list of size
     <replaceable>length</replaceable>, with each element
@@ -610,8 +638,9 @@ builtins.genList (x: x * x) 5
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.getAttr</function>
-  <replaceable>s</replaceable> <replaceable>set</replaceable></term>
+  <varlistentry xml:id='builtin-getAttr'>
+    <term><function>builtins.getAttr</function>
+    <replaceable>s</replaceable> <replaceable>set</replaceable></term>
 
     <listitem><para><function>getAttr</function> returns the attribute
     named <replaceable>s</replaceable> from
@@ -623,8 +652,9 @@ builtins.genList (x: x * x) 5
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.getEnv</function>
-  <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-getEnv'>
+    <term><function>builtins.getEnv</function>
+    <replaceable>s</replaceable></term>
 
     <listitem><para><function>getEnv</function> returns the value of
     the environment variable <replaceable>s</replaceable>, or an empty
@@ -641,8 +671,9 @@ builtins.genList (x: x * x) 5
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.hasAttr</function>
-  <replaceable>s</replaceable> <replaceable>set</replaceable></term>
+  <varlistentry xml:id='builtin-hasAttr'>
+    <term><function>builtins.hasAttr</function>
+    <replaceable>s</replaceable> <replaceable>set</replaceable></term>
 
     <listitem><para><function>hasAttr</function> returns
     <literal>true</literal> if <replaceable>set</replaceable> has an
@@ -655,8 +686,9 @@ builtins.genList (x: x * x) 5
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.hashString</function>
-  <replaceable>type</replaceable> <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-hashString'>
+    <term><function>builtins.hashString</function>
+    <replaceable>type</replaceable> <replaceable>s</replaceable></term>
 
     <listitem><para>Return a base-16 representation of the
     cryptographic hash of string <replaceable>s</replaceable>.  The
@@ -667,8 +699,9 @@ builtins.genList (x: x * x) 5
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.head</function>
-  <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-head'>
+    <term><function>builtins.head</function>
+    <replaceable>list</replaceable></term>
 
     <listitem><para>Return the first element of a list; abort
     evaluation if the argument isn’t a list or is an empty list.  You
@@ -678,8 +711,9 @@ builtins.genList (x: x * x) 5
   </varlistentry>
 
 
-  <varlistentry><term><function>import</function>
-  <replaceable>path</replaceable></term>
+  <varlistentry xml:id='builtin-import'>
+    <term><function>import</function>
+    <replaceable>path</replaceable></term>
 
     <listitem><para>Load, parse and return the Nix expression in the
     file <replaceable>path</replaceable>.  If <replaceable>path
@@ -733,8 +767,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.intersectAttrs</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-intersectAttrs'>
+    <term><function>builtins.intersectAttrs</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return a set consisting of the attributes in the
     set <replaceable>e2</replaceable> that also exist in the set
@@ -743,8 +778,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.isAttrs</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-isAttrs'>
+    <term><function>builtins.isAttrs</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
     <replaceable>e</replaceable> evaluates to a set, and
@@ -753,8 +789,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.isList</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-isList'>
+    <term><function>builtins.isList</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
     <replaceable>e</replaceable> evaluates to a list, and
@@ -763,7 +800,7 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.isFunction</function>
+  <varlistentry xml:id='builtin-isFunction'><term><function>builtins.isFunction</function>
   <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
@@ -773,8 +810,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.isString</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-isString'>
+    <term><function>builtins.isString</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
     <replaceable>e</replaceable> evaluates to a string, and
@@ -783,8 +821,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.isInt</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-isInt'>
+    <term><function>builtins.isInt</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
     <replaceable>e</replaceable> evaluates to an int, and
@@ -793,8 +832,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.isFloat</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-isFloat'>
+    <term><function>builtins.isFloat</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
     <replaceable>e</replaceable> evaluates to a float, and
@@ -803,8 +843,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.isBool</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-isBool'>
+    <term><function>builtins.isBool</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
     <replaceable>e</replaceable> evaluates to a bool, and
@@ -813,8 +854,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>isNull</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-isNull'>
+    <term><function>isNull</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if
     <replaceable>e</replaceable> evaluates to <literal>null</literal>,
@@ -828,8 +870,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.length</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-length'>
+    <term><function>builtins.length</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return the length of the list
     <replaceable>e</replaceable>.</para></listitem>
@@ -837,8 +880,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.lessThan</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-lessThan'>
+    <term><function>builtins.lessThan</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if the number
     <replaceable>e1</replaceable> is less than the number
@@ -850,8 +894,9 @@ x: x + 456</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.listToAttrs</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-listToAttrs'>
+    <term><function>builtins.listToAttrs</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Construct a set from a list specifying the names
     and values of each attribute.  Each element of the list should be
@@ -877,8 +922,9 @@ builtins.listToAttrs
 
   </varlistentry>
 
-  <varlistentry><term><function>map</function>
-  <replaceable>f</replaceable> <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-map'>
+    <term><function>map</function>
+    <replaceable>f</replaceable> <replaceable>list</replaceable></term>
 
     <listitem><para>Apply the function <replaceable>f</replaceable> to
     each element in the list <replaceable>list</replaceable>.  For
@@ -893,14 +939,15 @@ map (x: "foo" + x) [ "bar" "bla" "abc" ]</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.match</function>
-  <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
+  <varlistentry xml:id='builtin-match'>
+    <term><function>builtins.match</function>
+    <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
 
-  <listitem><para>Returns a list if the <link
-  xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
-  POSIX regular expression</link> <replaceable>regex</replaceable>
-  matches <replaceable>str</replaceable> precisely, otherwise returns
-  <literal>null</literal>.  Each item in the list is a regex group.
+    <listitem><para>Returns a list if the <link
+    xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
+    POSIX regular expression</link> <replaceable>regex</replaceable>
+    matches <replaceable>str</replaceable> precisely, otherwise returns
+    <literal>null</literal>.  Each item in the list is a regex group.
 
 <programlisting>
 builtins.match "ab" "abc"
@@ -926,11 +973,12 @@ builtins.match "[[:space:]]+([[:upper:]]+)[[:space:]]+" "  FOO   "
 
 Evaluates to <literal>[ "foo" ]</literal>.
 
-  </para></listitem>
+    </para></listitem>
   </varlistentry>
 
-  <varlistentry><term><function>builtins.mul</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-mul'>
+    <term><function>builtins.mul</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return the product of the numbers
     <replaceable>e1</replaceable> and
@@ -939,8 +987,9 @@ Evaluates to <literal>[ "foo" ]</literal>.
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.parseDrvName</function>
-  <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-parseDrvName'>
+    <term><function>builtins.parseDrvName</function>
+    <replaceable>s</replaceable></term>
 
     <listitem><para>Split the string <replaceable>s</replaceable> into
     a package name and version.  The package name is everything up to
@@ -953,7 +1002,7 @@ Evaluates to <literal>[ "foo" ]</literal>.
 
   </varlistentry>
 
-  <varlistentry>
+  <varlistentry xml:id='builtin-path'>
     <term>
       <function>builtins.path</function>
       <replaceable>args</replaceable>
@@ -1023,8 +1072,9 @@ Evaluates to <literal>[ "foo" ]</literal>.
     </listitem>
   </varlistentry>
 
-  <varlistentry><term><function>builtins.pathExists</function>
-  <replaceable>path</replaceable></term>
+  <varlistentry xml:id='builtin-pathExists'>
+    <term><function>builtins.pathExists</function>
+    <replaceable>path</replaceable></term>
 
     <listitem><para>Return <literal>true</literal> if the path
     <replaceable>path</replaceable> exists, and
@@ -1047,8 +1097,9 @@ in config.someSetting</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.readDir</function>
-  <replaceable>path</replaceable></term>
+  <varlistentry xml:id='builtin-readDir'>
+    <term><function>builtins.readDir</function>
+    <replaceable>path</replaceable></term>
 
     <listitem><para>Return the contents of the directory
     <replaceable>path</replaceable> as a set mapping directory entries
@@ -1069,8 +1120,9 @@ in config.someSetting</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.readFile</function>
-  <replaceable>path</replaceable></term>
+  <varlistentry xml:id='builtin-readFile'>
+    <term><function>builtins.readFile</function>
+    <replaceable>path</replaceable></term>
 
     <listitem><para>Return the contents of the file
     <replaceable>path</replaceable> as a string.</para></listitem>
@@ -1078,8 +1130,9 @@ in config.someSetting</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>removeAttrs</function>
-  <replaceable>set</replaceable> <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-removeAttrs'>
+    <term><function>removeAttrs</function>
+    <replaceable>set</replaceable> <replaceable>list</replaceable></term>
 
     <listitem><para>Remove the attributes listed in
     <replaceable>list</replaceable> from
@@ -1094,8 +1147,9 @@ removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.replaceStrings</function>
-  <replaceable>from</replaceable> <replaceable>to</replaceable> <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-replaceStrings'>
+    <term><function>builtins.replaceStrings</function>
+    <replaceable>from</replaceable> <replaceable>to</replaceable> <replaceable>s</replaceable></term>
 
     <listitem><para>Given string <replaceable>s</replaceable>, replace
     every occurrence of the strings in <replaceable>from</replaceable>
@@ -1111,8 +1165,9 @@ builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.seq</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-seq'>
+    <term><function>builtins.seq</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Evaluate <replaceable>e1</replaceable>, then
     evaluate and return <replaceable>e2</replaceable>. This ensures
@@ -1122,8 +1177,9 @@ builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.sort</function>
-  <replaceable>comparator</replaceable> <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-sort'>
+    <term><function>builtins.sort</function>
+    <replaceable>comparator</replaceable> <replaceable>list</replaceable></term>
 
     <listitem><para>Return <replaceable>list</replaceable> in sorted
     order. It repeatedly calls the function
@@ -1145,15 +1201,16 @@ builtins.sort builtins.lessThan [ 483 249 526 147 42 77 ]
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.split</function>
-  <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
+  <varlistentry xml:id='builtin-split'>
+    <term><function>builtins.split</function>
+    <replaceable>regex</replaceable> <replaceable>str</replaceable></term>
 
-  <listitem><para>Returns a list composed of non matched strings interleaved
-  with the lists of the <link
-  xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
-  POSIX regular expression</link> <replaceable>regex</replaceable> matches
-  of <replaceable>str</replaceable>. Each item in the lists of matched
-  sequences is a regex group.
+    <listitem><para>Returns a list composed of non matched strings interleaved
+    with the lists of the <link
+    xlink:href="http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04">extended
+    POSIX regular expression</link> <replaceable>regex</replaceable> matches
+    of <replaceable>str</replaceable>. Each item in the lists of matched
+    sequences is a regex group.
 
 <programlisting>
 builtins.split "(a)b" "abc"
@@ -1179,11 +1236,12 @@ builtins.split "([[:upper:]]+)" "  FOO   "
 
 Evaluates to <literal>[ "  " [ "FOO" ] "   " ]</literal>.
 
-  </para></listitem>
+    </para></listitem>
   </varlistentry>
 
-  <varlistentry><term><function>builtins.stringLength</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-stringLength'>
+    <term><function>builtins.stringLength</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return the length of the string
     <replaceable>e</replaceable>.  If <replaceable>e</replaceable> is
@@ -1192,8 +1250,9 @@ Evaluates to <literal>[ "  " [ "FOO" ] "   " ]</literal>.
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.sub</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-sub'>
+    <term><function>builtins.sub</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Return the difference between the numbers
     <replaceable>e1</replaceable> and
@@ -1202,9 +1261,10 @@ Evaluates to <literal>[ "  " [ "FOO" ] "   " ]</literal>.
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.substring</function>
-  <replaceable>start</replaceable> <replaceable>len</replaceable>
-  <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-substring'>
+    <term><function>builtins.substring</function>
+    <replaceable>start</replaceable> <replaceable>len</replaceable>
+    <replaceable>s</replaceable></term>
 
     <listitem><para>Return the substring of
     <replaceable>s</replaceable> from character position
@@ -1227,8 +1287,9 @@ builtins.substring 0 3 "nixos"
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.tail</function>
-  <replaceable>list</replaceable></term>
+  <varlistentry xml:id='builtin-tail'>
+    <term><function>builtins.tail</function>
+    <replaceable>list</replaceable></term>
 
     <listitem><para>Return the second to last elements of a list;
     abort evaluation if the argument isn’t a list or is an empty
@@ -1237,8 +1298,9 @@ builtins.substring 0 3 "nixos"
   </varlistentry>
 
 
-  <varlistentry><term><function>throw</function>
-  <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-throw'>
+    <term><function>throw</function>
+    <replaceable>s</replaceable></term>
 
     <listitem><para>Throw an error message
     <replaceable>s</replaceable>.  This usually aborts Nix expression
@@ -1251,9 +1313,10 @@ builtins.substring 0 3 "nixos"
   </varlistentry>
 
 
-  <varlistentry
-  xml:id='builtin-toFile'><term><function>builtins.toFile</function>
-  <replaceable>name</replaceable> <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-toFile'>
+    <term><function>builtins.toFile</function>
+    <replaceable>name</replaceable>
+    <replaceable>s</replaceable></term>
 
     <listitem><para>Store the string <replaceable>s</replaceable> in a
     file in the Nix store and return its path.  The file has suffix
@@ -1329,7 +1392,8 @@ in foo</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.toJSON</function> <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-toJSON'>
+    <term><function>builtins.toJSON</function> <replaceable>e</replaceable></term>
 
     <listitem><para>Return a string containing a JSON representation
     of <replaceable>e</replaceable>.  Strings, integers, floats, booleans,
@@ -1342,7 +1406,8 @@ in foo</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.toPath</function> <replaceable>s</replaceable></term>
+  <varlistentry xml:id='builtin-toPath'>
+    <term><function>builtins.toPath</function> <replaceable>s</replaceable></term>
 
     <listitem><para>Convert the string value
     <replaceable>s</replaceable> into a path value.  The string
@@ -1355,7 +1420,8 @@ in foo</programlisting>
   </varlistentry>
 
 
-  <varlistentry><term><function>toString</function> <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-toString'>
+    <term><function>toString</function> <replaceable>e</replaceable></term>
 
     <listitem><para>Convert the expression
     <replaceable>e</replaceable> to a string.
@@ -1374,7 +1440,8 @@ in foo</programlisting>
   </varlistentry>
 
 
-  <varlistentry xml:id='builtin-toXML'><term><function>builtins.toXML</function> <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-toXML'>
+    <term><function>builtins.toXML</function> <replaceable>e</replaceable></term>
 
     <listitem><para>Return a string containing an XML representation
     of <replaceable>e</replaceable>.  The main application for
@@ -1489,8 +1556,9 @@ stdenv.mkDerivation (rec {
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.trace</function>
-  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+  <varlistentry xml:id='builtin-trace'>
+    <term><function>builtins.trace</function>
+    <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
 
     <listitem><para>Evaluate <replaceable>e1</replaceable> and print its
     abstract syntax representation on standard error.  Then return
@@ -1499,8 +1567,9 @@ stdenv.mkDerivation (rec {
 
   </varlistentry>
 
-  <varlistentry><term><function>builtins.tryEval</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-tryEval'>
+    <term><function>builtins.tryEval</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Try to evaluate <replaceable>e</replaceable>.
     Return a set containing the attributes <literal>success</literal>
@@ -1513,8 +1582,9 @@ stdenv.mkDerivation (rec {
   </varlistentry>
 
 
-  <varlistentry><term><function>builtins.typeOf</function>
-  <replaceable>e</replaceable></term>
+  <varlistentry xml:id='builtin-typeOf'>
+    <term><function>builtins.typeOf</function>
+    <replaceable>e</replaceable></term>
 
     <listitem><para>Return a string representing the type of the value
     <replaceable>e</replaceable>, namely <literal>"int"</literal>,
diff --git a/doc/manual/packages/s3-substituter.xml b/doc/manual/packages/s3-substituter.xml
index bcd91cfdbccd..ea654392c6b1 100644
--- a/doc/manual/packages/s3-substituter.xml
+++ b/doc/manual/packages/s3-substituter.xml
@@ -12,8 +12,49 @@ from Amazon S3 and S3 compatible services. This uses the same
 <emphasis>binary</emphasis> cache mechanism that Nix usually uses to
 fetch prebuilt binaries from <uri>cache.nixos.org</uri>.</para>
 
+<para>The following options can be specified as URL parameters to
+the S3 URL:</para>
+
+<variablelist>
+  <varlistentry><term><literal>profile</literal></term>
+  <listitem>
+    <para>
+      The name of the AWS configuration profile to use. By default
+      Nix will use the <literal>default</literal> profile.
+    </para>
+  </listitem>
+  </varlistentry>
+
+  <varlistentry><term><literal>region</literal></term>
+  <listitem>
+    <para>
+      The region of the S3 bucket. <literal>us–east-1</literal> by
+      default.
+    </para>
+
+    <para>
+      If your bucket is not in <literal>us–east-1</literal>, you
+      should always explicitly specify the region parameter.
+    </para>
+  </listitem>
+  </varlistentry>
+
+  <varlistentry><term><literal>endpoint</literal></term>
+  <listitem>
+    <para>
+      The URL to your S3-compatible service, for when not using
+      Amazon S3. Do not specify this value if you're using Amazon
+      S3.
+    </para>
+    <note><para>This endpoint must support HTTPS and will use
+    path-based addressing instead of virtual host based
+    addressing.</para></note>
+  </listitem>
+  </varlistentry>
+</variablelist>
+
 <para>In this example we will use the bucket named
-<literal>example-bucket</literal>.</para>
+<literal>example-nix-cache</literal>.</para>
 
 <section xml:id="ssec-s3-substituter-anonymous-reads">
   <title>Anonymous Reads to your S3-compatible binary cache</title>
@@ -24,65 +65,56 @@ fetch prebuilt binaries from <uri>cache.nixos.org</uri>.</para>
   cache.</para>
 
   <para>For AWS S3 the binary cache URL for example bucket will be
-  exactly <uri>https://example-bucket.s3.amazonaws.com</uri>. For S3
-  compatible binary caches ago have to consult your software's
-  documentation.</para>
+  exactly <uri>https://example-nix-cache.s3.amazonaws.com</uri> or
+  <uri>s3://example-nix-cache</uri>. For S3 compatible binary caches,
+  consult that cache's documentation.</para>
 
   <para>Your bucket will need the following bucket policy:</para>
 
-  <programlisting>
-<![CDATA[
+  <programlisting><![CDATA[
 {
-  "Id": "DirectReads",
-  "Version": "2012-10-17",
-  "Statement": [
-    {
-      "Sid": "AlowDirectReads",
-      "Action": [
-        "s3:GetObject"
-      ],
-      "Effect": "Allow",
-      "Resource": "arn:aws:s3:::example-bucket/*",
-      "Principal": "*"
-    }
-  ]
+    "Id": "DirectReads",
+    "Version": "2012-10-17",
+    "Statement": [
+        {
+            "Sid": "AlowDirectReads",
+            "Action": [
+                "s3:GetObject",
+                "s3:GetBucketLocation"
+            ],
+            "Effect": "Allow",
+            "Resource": [
+                "arn:aws:s3:::example-nix-cache",
+                "arn:aws:s3:::example-nix-cache/*"
+            ],
+            "Principal": "*"
+        }
+    ]
 }
-]]>
-</programlisting>
+]]></programlisting>
 </section>
 
 <section xml:id="ssec-s3-substituter-authenticated-reads">
   <title>Authenticated Reads to your S3 binary cache</title>
 
   <para>For AWS S3 the binary cache URL for example bucket will be
-  exactly <uri>s3://example-bucket</uri>.</para>
+  exactly <uri>s3://example-nix-cache</uri>.</para>
 
   <para>Nix will use the <link
   xlink:href="https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/credentials.html#credentials-default.">default
   credential provider chain</link> for authenticating requests to
   Amazon S3.</para>
 
-  <para>Nix supports authenticated writes to S3 compatible binary
-  caches but only supports Authenticated reads from Amazon S3.
-  Additionally, the following limitations are in place for
-  authenticated reads:</para>
-
-  <itemizedlist>
-    <listitem><para>The bucket must actually be hosted by Amazon S3 and
-    <emphasis>not</emphasis> an S3 compatible
-    service.</para></listitem>
-
-    <listitem><para>The bucket must be within the
-    <literal>us-east-1</literal> region.</para></listitem>
-
-    <listitem><para>The Amazon credentials, if stored in a credential
-    profile, must be stored in the <literal>default</literal>
-    profile.</para></listitem>
-  </itemizedlist>
+  <para>Nix supports authenticated reads from Amazon S3 and S3
+  compatible binary caches.</para>
 
   <para>Your bucket will need a bucket policy allowing the desired
-  users to perform the <literal>s3:GetObject</literal> action on all
-  objects in the bucket.</para>
+  users to perform the <literal>s3:GetObject</literal> and
+  <literal>s3:GetBucketLocation</literal> action on all objects in the
+  bucket. The anonymous policy in <xref
+  linkend="ssec-s3-substituter-anonymous-reads" /> can be updated to
+  have a restricted <literal>Principal</literal> to support
+  this.</para>
 </section>
 
 
@@ -91,69 +123,49 @@ fetch prebuilt binaries from <uri>cache.nixos.org</uri>.</para>
 
   <para>Nix support fully supports writing to Amazon S3 and S3
   compatible buckets. The binary cache URL for our example bucket will
-  be <uri>s3://example-bucket</uri>.</para>
+  be <uri>s3://example-nix-cache</uri>.</para>
 
   <para>Nix will use the <link
   xlink:href="https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/credentials.html#credentials-default.">default
   credential provider chain</link> for authenticating requests to
   Amazon S3.</para>
 
-  <para>The following options can be specified as URL parameters to
-  the S3 URL:</para>
-  <variablelist>
-    <varlistentry><term><literal>profile</literal></term>
-    <listitem>
-      <para>
-        The name of the AWS configuration profile to use. By default
-        Nix will use the <literal>default</literal> profile.
-      </para>
-    </listitem>
-    </varlistentry>
-
-    <varlistentry><term><literal>region</literal></term>
-    <listitem>
-      <para>
-        The region of the S3 bucket. <literal>us–east-1</literal> by
-        default.
-      </para>
-    </listitem>
-    </varlistentry>
-
-    <varlistentry><term><literal>endpoint</literal></term>
-    <listitem>
-      <para>
-        The URL to your S3-compatible service, for when not using
-        Amazon S3. Do not specify this value if you're using Amazon
-        S3.
-      </para>
-      <note><para>This endpoint must support HTTPS and will use
-      path-based addressing instead of virtual host based
-      addressing.</para></note>
-    </listitem>
-    </varlistentry>
-  </variablelist>
-
-  <example><title>Uploading with non-default credential profile for Amazon S3</title>
-    <para><command>nix copy --to ssh://machine nixpkgs.hello s3://example-bucket?profile=cache-upload</command></para>
+  <para>Your account will need the following IAM policy to
+  upload to the cache:</para>
+
+  <programlisting><![CDATA[
+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Sid": "UploadToCache",
+      "Effect": "Allow",
+      "Action": [
+        "s3:AbortMultipartUpload",
+        "s3:GetBucketLocation",
+        "s3:GetObject",
+        "s3:ListBucket",
+        "s3:ListBucketMultipartUploads",
+        "s3:ListMultipartUploadParts",
+        "s3:ListObjects",
+        "s3:PutObject"
+      ],
+      "Resource": [
+        "arn:aws:s3:::example-nix-cache",
+        "arn:aws:s3:::example-nix-cache/*"
+      ]
+    }
+  ]
+}
+]]></programlisting>
+
+
+  <example><title>Uploading with a specific credential profile for Amazon S3</title>
+    <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&amp;region=eu-west-2' nixpkgs.hello</command></para>
   </example>
 
   <example><title>Uploading to an S3-Compatible Binary Cache</title>
-    <para><command>nix copy --to ssh://machine nixpkgs.hello s3://example-bucket?profile=cache-upload&amp;endpoint=minio.example.com</command></para>
+    <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&amp;endpoint=minio.example.com' nixpkgs.hello</command></para>
   </example>
-
-  <para>The user writing to the bucket will need to perform the
-  following actions against the bucket:</para>
-
-  <itemizedlist>
-    <listitem><para><literal>s3:ListBucket</literal></para></listitem>
-    <listitem><para><literal>s3:GetBucketLocation</literal></para></listitem>
-    <listitem><para><literal>s3:ListObjects</literal></para></listitem>
-    <listitem><para><literal>s3:GetObject</literal></para></listitem>
-    <listitem><para><literal>s3:PutObject</literal></para></listitem>
-    <listitem><para><literal>s3:ListBucketMultipartUploads</literal></para></listitem>
-    <listitem><para><literal>s3:CreateMultipartUpload</literal></para></listitem>
-    <listitem><para><literal>s3:ListMultipartUploadParts</literal></para></listitem>
-    <listitem><para><literal>s3:AbortMultipartUpload</literal></para></listitem>
-  </itemizedlist>
 </section>
 </section>
diff --git a/doc/manual/release-notes/release-notes.xml b/doc/manual/release-notes/release-notes.xml
index ff4085cb792d..e8ff586fa43f 100644
--- a/doc/manual/release-notes/release-notes.xml
+++ b/doc/manual/release-notes/release-notes.xml
@@ -12,6 +12,7 @@
 </partintro>
 -->
 
+<xi:include href="rl-2.2.xml" />
 <xi:include href="rl-2.1.xml" />
 <xi:include href="rl-2.0.xml" />
 <xi:include href="rl-1.11.10.xml" />
diff --git a/doc/manual/release-notes/rl-2.2.xml b/doc/manual/release-notes/rl-2.2.xml
new file mode 100644
index 000000000000..bc28a56c9401
--- /dev/null
+++ b/doc/manual/release-notes/rl-2.2.xml
@@ -0,0 +1,25 @@
+<section xmlns="http://docbook.org/ns/docbook"
+      xmlns:xlink="http://www.w3.org/1999/xlink"
+      xmlns:xi="http://www.w3.org/2001/XInclude"
+      version="5.0"
+      xml:id="ssec-relnotes-2.2">
+
+<title>Release 2.2 (201?-??-??)</title>
+
+<para>This release has the following changes:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>The derivation attribute
+    <varname>requiredSystemFeatures</varname> is now enforced for
+    local builds, and not just to route builds to remote builders.
+    The supported features of a machine can be specified through the
+    configuration setting <varname>system-features</varname>.
+    </para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
diff --git a/scripts/nix-profile-daemon.sh.in b/scripts/nix-profile-daemon.sh.in
index 1be9a0755d85..87d9fe5061a7 100644
--- a/scripts/nix-profile-daemon.sh.in
+++ b/scripts/nix-profile-daemon.sh.in
@@ -68,4 +68,4 @@ elif [ -e "/nix/var/nix/profiles/default/etc/ssl/certs/ca-bundle.crt" ]; then #
 fi
 
 export NIX_PATH="nixpkgs=@localstatedir@/nix/profiles/per-user/root/channels/nixpkgs:@localstatedir@/nix/profiles/per-user/root/channels"
-export PATH="$HOME/.nix-profile/bin:$HOME/.nix-profile/lib/kde4/libexec:@localstatedir@/nix/profiles/default/bin:@localstatedir@/nix/profiles/default:@localstatedir@/nix/profiles/default/lib/kde4/libexec:$PATH"
+export PATH="$HOME/.nix-profile/bin:@localstatedir@/nix/profiles/default/bin:$PATH"
diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 1402bd097c35..0073b9b727ec 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -11,6 +11,7 @@
 #include "compression.hh"
 #include "json.hh"
 #include "nar-info.hh"
+#include "parsed-derivations.hh"
 
 #include <algorithm>
 #include <iostream>
@@ -740,6 +741,8 @@ private:
     /* The derivation stored at drvPath. */
     std::unique_ptr<BasicDerivation> drv;
 
+    std::unique_ptr<ParsedDerivation> parsedDrv;
+
     /* The remainder is state held during the build. */
 
     /* Locks on the output paths. */
@@ -1139,6 +1142,8 @@ void DerivationGoal::haveDerivation()
         return;
     }
 
+    parsedDrv = std::make_unique<ParsedDerivation>(drvPath, *drv);
+
     /* We are first going to try to create the invalid output paths
        through substitutes.  If that doesn't work, we'll build
        them. */
@@ -1395,7 +1400,7 @@ void DerivationGoal::tryToBuild()
     /* Don't do a remote build if the derivation has the attribute
        `preferLocalBuild' set.  Also, check and repair modes are only
        supported for local builds. */
-    bool buildLocally = buildMode != bmNormal || drv->willBuildLocally();
+    bool buildLocally = buildMode != bmNormal || parsedDrv->willBuildLocally();
 
     auto started = [&]() {
         auto msg = fmt(
@@ -1641,19 +1646,13 @@ HookReply DerivationGoal::tryBuildHook()
 
     try {
 
-        /* Tell the hook about system features (beyond the system type)
-           required from the build machine.  (The hook could parse the
-           drv file itself, but this is easier.) */
-        Strings features = tokenizeString<Strings>(get(drv->env, "requiredSystemFeatures"));
-        for (auto & i : features) checkStoreName(i); /* !!! abuse */
-
         /* Send the request to the hook. */
         worker.hook->sink
             << "try"
             << (worker.getNrLocalBuilds() < settings.maxBuildJobs ? 1 : 0)
             << drv->platform
             << drvPath
-            << features;
+            << parsedDrv->getRequiredSystemFeatures();
         worker.hook->sink.flush();
 
         /* Read the first line of input, which should be a word indicating
@@ -1793,23 +1792,26 @@ static void preloadNSS() {
 void DerivationGoal::startBuilder()
 {
     /* Right platform? */
-    if (!drv->canBuildLocally()) {
-        throw Error(
-            format("a '%1%' is required to build '%3%', but I am a '%2%'")
-            % drv->platform % settings.thisSystem % drvPath);
-    }
+    if (!parsedDrv->canBuildLocally())
+        throw Error("a '%s' with features {%s} is required to build '%s', but I am a '%s' with features {%s}",
+            drv->platform,
+            concatStringsSep(", ", parsedDrv->getRequiredSystemFeatures()),
+            drvPath,
+            settings.thisSystem,
+            concatStringsSep(", ", settings.systemFeatures));
 
     if (drv->isBuiltin())
         preloadNSS();
 
 #if __APPLE__
-    additionalSandboxProfile = get(drv->env, "__sandboxProfile");
+    additionalSandboxProfile = parsedDrv->getStringAttr("__sandboxProfile").value_or("");
 #endif
 
     /* Are we doing a chroot build? */
     {
+        auto noChroot = parsedDrv->getBoolAttr("__noChroot");
         if (settings.sandboxMode == smEnabled) {
-            if (get(drv->env, "__noChroot") == "1")
+            if (noChroot)
                 throw Error(format("derivation '%1%' has '__noChroot' set, "
                     "but that's not allowed when 'sandbox' is 'true'") % drvPath);
 #if __APPLE__
@@ -1822,7 +1824,7 @@ void DerivationGoal::startBuilder()
         else if (settings.sandboxMode == smDisabled)
             useChroot = false;
         else if (settings.sandboxMode == smRelaxed)
-            useChroot = !fixedOutput && get(drv->env, "__noChroot") != "1";
+            useChroot = !fixedOutput && !noChroot;
     }
 
     if (worker.store.storeDir != worker.store.realStoreDir) {
@@ -1873,7 +1875,7 @@ void DerivationGoal::startBuilder()
     writeStructuredAttrs();
 
     /* Handle exportReferencesGraph(), if set. */
-    if (!drv->env.count("__json")) {
+    if (!parsedDrv->getStructuredAttrs()) {
         /* The `exportReferencesGraph' feature allows the references graph
            to be passed to a builder.  This attribute should be a list of
            pairs [name1 path1 name2 path2 ...].  The references graph of
@@ -1938,7 +1940,7 @@ void DerivationGoal::startBuilder()
         PathSet allowedPaths = settings.allowedImpureHostPrefixes;
 
         /* This works like the above, except on a per-derivation level */
-        Strings impurePaths = tokenizeString<Strings>(get(drv->env, "__impureHostDeps"));
+        auto impurePaths = parsedDrv->getStringsAttr("__impureHostDeps").value_or(Strings());
 
         for (auto & i : impurePaths) {
             bool found = false;
@@ -2306,7 +2308,7 @@ void DerivationGoal::initEnv()
        passAsFile is ignored in structure mode because it's not
        needed (attributes are not passed through the environment, so
        there is no size constraint). */
-    if (!drv->env.count("__json")) {
+    if (!parsedDrv->getStructuredAttrs()) {
 
         StringSet passAsFile = tokenizeString<StringSet>(get(drv->env, "passAsFile"));
         int fileNr = 0;
@@ -2353,8 +2355,8 @@ void DerivationGoal::initEnv()
        fixed-output derivations is by definition pure (since we
        already know the cryptographic hash of the output). */
     if (fixedOutput) {
-        Strings varNames = tokenizeString<Strings>(get(drv->env, "impureEnvVars"));
-        for (auto & i : varNames) env[i] = getEnv(i);
+        for (auto & i : parsedDrv->getStringsAttr("impureEnvVars").value_or(Strings()))
+            env[i] = getEnv(i);
     }
 
     /* Currently structured log messages piggyback on stderr, but we
@@ -2369,111 +2371,103 @@ static std::regex shVarName("[A-Za-z_][A-Za-z0-9_]*");
 
 void DerivationGoal::writeStructuredAttrs()
 {
-    auto jsonAttr = drv->env.find("__json");
-    if (jsonAttr == drv->env.end()) return;
-
-    try {
-
-        auto jsonStr = rewriteStrings(jsonAttr->second, inputRewrites);
+    auto & structuredAttrs = parsedDrv->getStructuredAttrs();
+    if (!structuredAttrs) return;
 
-        auto json = nlohmann::json::parse(jsonStr);
+    auto json = *structuredAttrs;
 
-        /* Add an "outputs" object containing the output paths. */
-        nlohmann::json outputs;
-        for (auto & i : drv->outputs)
-            outputs[i.first] = rewriteStrings(i.second.path, inputRewrites);
-        json["outputs"] = outputs;
-
-        /* Handle exportReferencesGraph. */
-        auto e = json.find("exportReferencesGraph");
-        if (e != json.end() && e->is_object()) {
-            for (auto i = e->begin(); i != e->end(); ++i) {
-                std::ostringstream str;
-                {
-                    JSONPlaceholder jsonRoot(str, true);
-                    PathSet storePaths;
-                    for (auto & p : *i)
-                        storePaths.insert(p.get<std::string>());
-                    worker.store.pathInfoToJSON(jsonRoot,
-                        exportReferences(storePaths), false, true);
-                }
-                json[i.key()] = nlohmann::json::parse(str.str()); // urgh
+    /* Add an "outputs" object containing the output paths. */
+    nlohmann::json outputs;
+    for (auto & i : drv->outputs)
+        outputs[i.first] = rewriteStrings(i.second.path, inputRewrites);
+    json["outputs"] = outputs;
+
+    /* Handle exportReferencesGraph. */
+    auto e = json.find("exportReferencesGraph");
+    if (e != json.end() && e->is_object()) {
+        for (auto i = e->begin(); i != e->end(); ++i) {
+            std::ostringstream str;
+            {
+                JSONPlaceholder jsonRoot(str, true);
+                PathSet storePaths;
+                for (auto & p : *i)
+                    storePaths.insert(p.get<std::string>());
+                worker.store.pathInfoToJSON(jsonRoot,
+                    exportReferences(storePaths), false, true);
             }
+            json[i.key()] = nlohmann::json::parse(str.str()); // urgh
         }
+    }
 
-        writeFile(tmpDir + "/.attrs.json", json.dump());
-
-        /* As a convenience to bash scripts, write a shell file that
-           maps all attributes that are representable in bash -
-           namely, strings, integers, nulls, Booleans, and arrays and
-           objects consisting entirely of those values. (So nested
-           arrays or objects are not supported.) */
+    writeFile(tmpDir + "/.attrs.json", rewriteStrings(json.dump(), inputRewrites));
 
-        auto handleSimpleType = [](const nlohmann::json & value) -> std::experimental::optional<std::string> {
-            if (value.is_string())
-                return shellEscape(value);
+    /* As a convenience to bash scripts, write a shell file that
+       maps all attributes that are representable in bash -
+       namely, strings, integers, nulls, Booleans, and arrays and
+       objects consisting entirely of those values. (So nested
+       arrays or objects are not supported.) */
 
-            if (value.is_number()) {
-                auto f = value.get<float>();
-                if (std::ceil(f) == f)
-                    return std::to_string(value.get<int>());
-            }
+    auto handleSimpleType = [](const nlohmann::json & value) -> std::experimental::optional<std::string> {
+        if (value.is_string())
+            return shellEscape(value);
 
-            if (value.is_null())
-                return std::string("''");
+        if (value.is_number()) {
+            auto f = value.get<float>();
+            if (std::ceil(f) == f)
+                return std::to_string(value.get<int>());
+        }
 
-            if (value.is_boolean())
-                return value.get<bool>() ? std::string("1") : std::string("");
+        if (value.is_null())
+            return std::string("''");
 
-            return {};
-        };
+        if (value.is_boolean())
+            return value.get<bool>() ? std::string("1") : std::string("");
 
-        std::string jsonSh;
+        return {};
+    };
 
-        for (auto i = json.begin(); i != json.end(); ++i) {
+    std::string jsonSh;
 
-            if (!std::regex_match(i.key(), shVarName)) continue;
+    for (auto i = json.begin(); i != json.end(); ++i) {
 
-            auto & value = i.value();
+        if (!std::regex_match(i.key(), shVarName)) continue;
 
-            auto s = handleSimpleType(value);
-            if (s)
-                jsonSh += fmt("declare %s=%s\n", i.key(), *s);
+        auto & value = i.value();
 
-            else if (value.is_array()) {
-                std::string s2;
-                bool good = true;
+        auto s = handleSimpleType(value);
+        if (s)
+            jsonSh += fmt("declare %s=%s\n", i.key(), *s);
 
-                for (auto i = value.begin(); i != value.end(); ++i) {
-                    auto s3 = handleSimpleType(i.value());
-                    if (!s3) { good = false; break; }
-                    s2 += *s3; s2 += ' ';
-                }
+        else if (value.is_array()) {
+            std::string s2;
+            bool good = true;
 
-                if (good)
-                    jsonSh += fmt("declare -a %s=(%s)\n", i.key(), s2);
+            for (auto i = value.begin(); i != value.end(); ++i) {
+                auto s3 = handleSimpleType(i.value());
+                if (!s3) { good = false; break; }
+                s2 += *s3; s2 += ' ';
             }
 
-            else if (value.is_object()) {
-                std::string s2;
-                bool good = true;
+            if (good)
+                jsonSh += fmt("declare -a %s=(%s)\n", i.key(), s2);
+        }
 
-                for (auto i = value.begin(); i != value.end(); ++i) {
-                    auto s3 = handleSimpleType(i.value());
-                    if (!s3) { good = false; break; }
-                    s2 += fmt("[%s]=%s ", shellEscape(i.key()), *s3);
-                }
+        else if (value.is_object()) {
+            std::string s2;
+            bool good = true;
 
-                if (good)
-                    jsonSh += fmt("declare -A %s=(%s)\n", i.key(), s2);
+            for (auto i = value.begin(); i != value.end(); ++i) {
+                auto s3 = handleSimpleType(i.value());
+                if (!s3) { good = false; break; }
+                s2 += fmt("[%s]=%s ", shellEscape(i.key()), *s3);
             }
-        }
-
-        writeFile(tmpDir + "/.attrs.sh", jsonSh);
 
-    } catch (std::exception & e) {
-        throw Error("cannot process __json attribute of '%s': %s", drvPath, e.what());
+            if (good)
+                jsonSh += fmt("declare -A %s=(%s)\n", i.key(), s2);
+        }
     }
+
+    writeFile(tmpDir + "/.attrs.sh", rewriteStrings(jsonSh, inputRewrites));
 }
 
 
@@ -2628,7 +2622,7 @@ void DerivationGoal::runChild()
                 createDirs(chrootRootDir + "/dev/shm");
                 createDirs(chrootRootDir + "/dev/pts");
                 ss.push_back("/dev/full");
-                if (pathExists("/dev/kvm"))
+                if (settings.systemFeatures.get().count("kvm") && pathExists("/dev/kvm"))
                     ss.push_back("/dev/kvm");
                 ss.push_back("/dev/null");
                 ss.push_back("/dev/random");
@@ -2917,7 +2911,7 @@ void DerivationGoal::runChild()
 
             writeFile(sandboxFile, sandboxProfile);
 
-            bool allowLocalNetworking = get(drv->env, "__darwinAllowLocalNetworking") == "1";
+            bool allowLocalNetworking = parsedDrv->getBoolAttr("__darwinAllowLocalNetworking");
 
             /* The tmpDir in scope points at the temporary build directory for our derivation. Some packages try different mechanisms
                to find temporary directories, so we want to open up a broader place for them to dump their files, if needed. */
@@ -2989,10 +2983,9 @@ void DerivationGoal::runChild()
 /* Parse a list of reference specifiers.  Each element must either be
    a store path, or the symbolic name of the output of the derivation
    (such as `out'). */
-PathSet parseReferenceSpecifiers(Store & store, const BasicDerivation & drv, string attr)
+PathSet parseReferenceSpecifiers(Store & store, const BasicDerivation & drv, const Strings & paths)
 {
     PathSet result;
-    Paths paths = tokenizeString<Paths>(attr);
     for (auto & i : paths) {
         if (store.isStorePath(i))
             result.insert(i);
@@ -3121,7 +3114,7 @@ void DerivationGoal::registerOutputs()
                the derivation to its content-addressed location. */
             Hash h2 = recursive ? hashPath(h.type, actualPath).first : hashFile(h.type, actualPath);
 
-            Path dest = worker.store.makeFixedOutputPath(recursive, h2, drv->env["name"]);
+            Path dest = worker.store.makeFixedOutputPath(recursive, h2, storePathToName(path));
 
             if (h != h2) {
 
@@ -3204,9 +3197,10 @@ void DerivationGoal::registerOutputs()
 
         /* Enforce `allowedReferences' and friends. */
         auto checkRefs = [&](const string & attrName, bool allowed, bool recursive) {
-            if (drv->env.find(attrName) == drv->env.end()) return;
+            auto value = parsedDrv->getStringsAttr(attrName);
+            if (!value) return;
 
-            PathSet spec = parseReferenceSpecifiers(worker.store, *drv, get(drv->env, attrName));
+            PathSet spec = parseReferenceSpecifiers(worker.store, *drv, *value);
 
             PathSet used;
             if (recursive) {
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 1e187ec5e954..3961126fff9c 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -36,12 +36,6 @@ Path BasicDerivation::findOutput(const string & id) const
 }
 
 
-bool BasicDerivation::willBuildLocally() const
-{
-    return get(env, "preferLocalBuild") == "1" && canBuildLocally();
-}
-
-
 bool BasicDerivation::substitutesAllowed() const
 {
     return get(env, "allowSubstitutes", "1") == "1";
@@ -54,14 +48,6 @@ bool BasicDerivation::isBuiltin() const
 }
 
 
-bool BasicDerivation::canBuildLocally() const
-{
-    return platform == settings.thisSystem
-        || settings.extraPlatforms.get().count(platform) > 0
-        || isBuiltin();
-}
-
-
 Path writeDerivation(ref<Store> store,
     const Derivation & drv, const string & name, RepairFlag repair)
 {
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 7b97730d3bf2..9753e796db5f 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -56,14 +56,10 @@ struct BasicDerivation
        the given derivation. */
     Path findOutput(const string & id) const;
 
-    bool willBuildLocally() const;
-
     bool substitutesAllowed() const;
 
     bool isBuiltin() const;
 
-    bool canBuildLocally() const;
-
     /* Return true iff this is a fixed-output derivation. */
     bool isFixedOutput() const;
 
diff --git a/src/libstore/download.cc b/src/libstore/download.cc
index 13913d031daa..f44f1836b31e 100644
--- a/src/libstore/download.cc
+++ b/src/libstore/download.cc
@@ -710,11 +710,12 @@ void Downloader::download(DownloadRequest && request, Sink & sink)
 
         /* If the buffer is full, then go to sleep until the calling
            thread wakes us up (i.e. when it has removed data from the
-           buffer). Note: this does stall the download thread. */
-        while (state->data.size() > 1024 * 1024) {
-            if (state->quit) return;
+           buffer). We don't wait forever to prevent stalling the
+           download thread. (Hopefully sleeping will throttle the
+           sender.) */
+        if (state->data.size() > 1024 * 1024) {
             debug("download buffer is full; going to sleep");
-            state.wait(state->request);
+            state.wait_for(state->request, std::chrono::seconds(10));
         }
 
         /* Append data to the buffer and wake up the calling
@@ -736,30 +737,36 @@ void Downloader::download(DownloadRequest && request, Sink & sink)
             state->request.notify_one();
         }});
 
-    auto state(_state->lock());
-
     while (true) {
         checkInterrupt();
 
-        /* If no data is available, then wait for the download thread
-           to wake us up. */
-        if (state->data.empty()) {
+        std::string chunk;
+
+        /* Grab data if available, otherwise wait for the download
+           thread to wake us up. */
+        {
+            auto state(_state->lock());
+
+            while (state->data.empty()) {
 
-            if (state->quit) {
-                if (state->exc) std::rethrow_exception(state->exc);
-                break;
+                if (state->quit) {
+                    if (state->exc) std::rethrow_exception(state->exc);
+                    return;
+                }
+
+                state.wait(state->avail);
             }
 
-            state.wait(state->avail);
-        }
+            chunk = std::move(state->data);
 
-        /* If data is available, then flush it to the sink and wake up
-           the download thread if it's blocked on a full buffer. */
-        if (!state->data.empty()) {
-            sink((unsigned char *) state->data.data(), state->data.size());
-            state->data.clear();
             state->request.notify_one();
         }
+
+        /* Flush the data to the sink and wake up the download thread
+           if it's blocked on a full buffer. We don't hold the state
+           lock while doing this to prevent blocking the download
+           thread if sink() takes a long time. */
+        sink((unsigned char *) chunk.data(), chunk.size());
     }
 }
 
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index d95db56726cb..a9c07b23a6f3 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -86,6 +86,21 @@ unsigned int Settings::getDefaultCores()
     return std::max(1U, std::thread::hardware_concurrency());
 }
 
+StringSet Settings::getDefaultSystemFeatures()
+{
+    /* For backwards compatibility, accept some "features" that are
+       used in Nixpkgs to route builds to certain machines but don't
+       actually require anything special on the machines. */
+    StringSet features{"nixos-test", "benchmark", "big-parallel"};
+
+    #if __linux__
+    if (access("/dev/kvm", R_OK | W_OK) == 0)
+        features.insert("kvm");
+    #endif
+
+    return features;
+}
+
 const string nixVersion = PACKAGE_VERSION;
 
 template<> void BaseSetting<SandboxMode>::set(const std::string & str)
diff --git a/src/libstore/globals.hh b/src/libstore/globals.hh
index f589078dbb98..cf4ae63cdc2f 100644
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -32,6 +32,8 @@ class Settings : public Config {
 
     unsigned int getDefaultCores();
 
+    StringSet getDefaultSystemFeatures();
+
 public:
 
     Settings();
@@ -261,6 +263,10 @@ public:
         "These may be supported natively (e.g. armv7 on some aarch64 CPUs "
         "or using hacks like qemu-user."};
 
+    Setting<StringSet> systemFeatures{this, getDefaultSystemFeatures(),
+        "system-features",
+        "Optional features that this system implements (like \"kvm\")."};
+
     Setting<Strings> substituters{this,
         nixStore == "/nix/store" ? Strings{"https://cache.nixos.org/"} : Strings(),
         "substituters",
diff --git a/src/libstore/parsed-derivations.cc b/src/libstore/parsed-derivations.cc
new file mode 100644
index 000000000000..dc3286482736
--- /dev/null
+++ b/src/libstore/parsed-derivations.cc
@@ -0,0 +1,111 @@
+#include "parsed-derivations.hh"
+
+namespace nix {
+
+ParsedDerivation::ParsedDerivation(const Path & drvPath, BasicDerivation & drv)
+    : drvPath(drvPath), drv(drv)
+{
+    /* Parse the __json attribute, if any. */
+    auto jsonAttr = drv.env.find("__json");
+    if (jsonAttr != drv.env.end()) {
+        try {
+            structuredAttrs = nlohmann::json::parse(jsonAttr->second);
+        } catch (std::exception & e) {
+            throw Error("cannot process __json attribute of '%s': %s", drvPath, e.what());
+        }
+    }
+}
+
+std::experimental::optional<std::string> ParsedDerivation::getStringAttr(const std::string & name) const
+{
+    if (structuredAttrs) {
+        auto i = structuredAttrs->find(name);
+        if (i == structuredAttrs->end())
+            return {};
+        else {
+            if (!i->is_string())
+                throw Error("attribute '%s' of derivation '%s' must be a string", name, drvPath);
+            return i->get<std::string>();
+        }
+    } else {
+        auto i = drv.env.find(name);
+        if (i == drv.env.end())
+            return {};
+        else
+            return i->second;
+    }
+}
+
+bool ParsedDerivation::getBoolAttr(const std::string & name, bool def) const
+{
+    if (structuredAttrs) {
+        auto i = structuredAttrs->find(name);
+        if (i == structuredAttrs->end())
+            return def;
+        else {
+            if (!i->is_boolean())
+                throw Error("attribute '%s' of derivation '%s' must be a Boolean", name, drvPath);
+            return i->get<bool>();
+        }
+    } else {
+        auto i = drv.env.find(name);
+        if (i == drv.env.end())
+            return def;
+        else
+            return i->second == "1";
+    }
+}
+
+std::experimental::optional<Strings> ParsedDerivation::getStringsAttr(const std::string & name) const
+{
+    if (structuredAttrs) {
+        auto i = structuredAttrs->find(name);
+        if (i == structuredAttrs->end())
+            return {};
+        else {
+            if (!i->is_array())
+                throw Error("attribute '%s' of derivation '%s' must be a list of strings", name, drvPath);
+            Strings res;
+            for (auto j = i->begin(); j != i->end(); ++j) {
+                if (!j->is_string())
+                    throw Error("attribute '%s' of derivation '%s' must be a list of strings", name, drvPath);
+                res.push_back(j->get<std::string>());
+            }
+            return res;
+        }
+    } else {
+        auto i = drv.env.find(name);
+        if (i == drv.env.end())
+            return {};
+        else
+            return tokenizeString<Strings>(i->second);
+    }
+}
+
+StringSet ParsedDerivation::getRequiredSystemFeatures() const
+{
+    StringSet res;
+    for (auto & i : getStringsAttr("requiredSystemFeatures").value_or(Strings()))
+        res.insert(i);
+    return res;
+}
+
+bool ParsedDerivation::canBuildLocally() const
+{
+    if (drv.platform != settings.thisSystem.get()
+        && !settings.extraPlatforms.get().count(drv.platform)
+        && !drv.isBuiltin())
+        return false;
+
+    for (auto & feature : getRequiredSystemFeatures())
+        if (!settings.systemFeatures.get().count(feature)) return false;
+
+    return true;
+}
+
+bool ParsedDerivation::willBuildLocally() const
+{
+    return getBoolAttr("preferLocalBuild") && canBuildLocally();
+}
+
+}
diff --git a/src/libstore/parsed-derivations.hh b/src/libstore/parsed-derivations.hh
new file mode 100644
index 000000000000..0a82c146172b
--- /dev/null
+++ b/src/libstore/parsed-derivations.hh
@@ -0,0 +1,35 @@
+#include "derivations.hh"
+
+#include <nlohmann/json.hpp>
+
+namespace nix {
+
+class ParsedDerivation
+{
+    Path drvPath;
+    BasicDerivation & drv;
+    std::experimental::optional<nlohmann::json> structuredAttrs;
+
+public:
+
+    ParsedDerivation(const Path & drvPath, BasicDerivation & drv);
+
+    const std::experimental::optional<nlohmann::json> & getStructuredAttrs() const
+    {
+        return structuredAttrs;
+    }
+
+    std::experimental::optional<std::string> getStringAttr(const std::string & name) const;
+
+    bool getBoolAttr(const std::string & name, bool def = false) const;
+
+    std::experimental::optional<Strings> getStringsAttr(const std::string & name) const;
+
+    StringSet getRequiredSystemFeatures() const;
+
+    bool canBuildLocally() const;
+
+    bool willBuildLocally() const;
+};
+
+}
diff --git a/src/libstore/s3-binary-cache-store.cc b/src/libstore/s3-binary-cache-store.cc
index 7711388f05a9..ba11ce6bb6de 100644
--- a/src/libstore/s3-binary-cache-store.cc
+++ b/src/libstore/s3-binary-cache-store.cc
@@ -19,8 +19,6 @@
 #include <aws/core/utils/logging/LogMacros.h>
 #include <aws/core/utils/threading/Executor.h>
 #include <aws/s3/S3Client.h>
-#include <aws/s3/model/CreateBucketRequest.h>
-#include <aws/s3/model/GetBucketLocationRequest.h>
 #include <aws/s3/model/GetObjectRequest.h>
 #include <aws/s3/model/HeadObjectRequest.h>
 #include <aws/s3/model/ListObjectsRequest.h>
@@ -202,32 +200,6 @@ struct S3BinaryCacheStoreImpl : public S3BinaryCacheStore
     {
         if (!diskCache->cacheExists(getUri(), wantMassQuery_, priority)) {
 
-            /* Create the bucket if it doesn't already exists. */
-            // FIXME: HeadBucket would be more appropriate, but doesn't return
-            // an easily parsed 404 message.
-            auto res = s3Helper.client->GetBucketLocation(
-                Aws::S3::Model::GetBucketLocationRequest().WithBucket(bucketName));
-
-            if (!res.IsSuccess()) {
-                if (res.GetError().GetErrorType() != Aws::S3::S3Errors::NO_SUCH_BUCKET)
-                    throw Error(format("AWS error checking bucket '%s': %s") % bucketName % res.GetError().GetMessage());
-
-                printInfo("creating S3 bucket '%s'...", bucketName);
-
-                // Stupid S3 bucket locations.
-                auto bucketConfig = Aws::S3::Model::CreateBucketConfiguration();
-                if (s3Helper.config->region != "us-east-1")
-                    bucketConfig.SetLocationConstraint(
-                        Aws::S3::Model::BucketLocationConstraintMapper::GetBucketLocationConstraintForName(
-                            s3Helper.config->region));
-
-                checkAws(format("AWS error creating bucket '%s'") % bucketName,
-                    s3Helper.client->CreateBucket(
-                        Aws::S3::Model::CreateBucketRequest()
-                        .WithBucket(bucketName)
-                        .WithCreateBucketConfiguration(bucketConfig)));
-            }
-
             BinaryCacheStore::init();
 
             diskCache->createCache(getUri(), storeDir, wantMassQuery_, priority);
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 1f42097fccfb..2c0f68651e4f 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -610,7 +610,7 @@ void copyStorePath(ref<Store> srcStore, ref<Store> dstStore,
         });
         srcStore->narFromPath({storePath}, wrapperSink);
     }, [&]() {
-	throw EndOfFile("NAR for '%s' fetched from '%s' is incomplete", storePath, srcStore->getUri());
+        throw EndOfFile("NAR for '%s' fetched from '%s' is incomplete", storePath, srcStore->getUri());
     });
 
     dstStore->addToStore(*info, *source, repair, checkSigs);
diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 31df6fdfde86..0e75eeec2bfe 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -169,17 +169,13 @@ std::unique_ptr<Source> sinkToSource(
     {
         typedef boost::coroutines2::coroutine<std::string> coro_t;
 
+        std::function<void(Sink &)> fun;
         std::function<void()> eof;
-        coro_t::pull_type coro;
+        std::experimental::optional<coro_t::pull_type> coro;
+        bool started = false;
 
         SinkToSource(std::function<void(Sink &)> fun, std::function<void()> eof)
-            : eof(eof)
-            , coro([&](coro_t::push_type & yield) {
-                LambdaSink sink([&](const unsigned char * data, size_t len) {
-                    if (len) yield(std::string((const char *) data, len));
-                });
-                fun(sink);
-            })
+            : fun(fun), eof(eof)
         {
         }
 
@@ -188,11 +184,19 @@ std::unique_ptr<Source> sinkToSource(
 
         size_t read(unsigned char * data, size_t len) override
         {
-            if (!coro) { eof(); abort(); }
+            if (!coro)
+                coro = coro_t::pull_type([&](coro_t::push_type & yield) {
+                    LambdaSink sink([&](const unsigned char * data, size_t len) {
+                            if (len) yield(std::string((const char *) data, len));
+                        });
+                    fun(sink);
+                });
+
+            if (!*coro) { eof(); abort(); }
 
             if (pos == cur.size()) {
-                if (!cur.empty()) coro();
-                cur = coro.get();
+                if (!cur.empty()) (*coro)();
+                cur = coro->get();
                 pos = 0;
             }
 
diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index 94d3a27560fe..b78f3d9e424e 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -417,16 +417,20 @@ void mainWrapped(int argc, char * * argv)
                 "dontAddDisableDepTrack=1; "
                 "[ -e $stdenv/setup ] && source $stdenv/setup; "
                 "%3%"
+                "PATH=\"%4%:$PATH\"; "
+                "SHELL=%5%; "
                 "set +e; "
                 R"s([ -n "$PS1" ] && PS1='\n\[\033[1;32m\][nix-shell:\w]\$\[\033[0m\] '; )s"
                 "if [ \"$(type -t runHook)\" = function ]; then runHook shellHook; fi; "
                 "unset NIX_ENFORCE_PURITY; "
                 "shopt -u nullglob; "
-                "unset TZ; %4%"
-                "%5%",
+                "unset TZ; %6%"
+                "%7%",
                 (Path) tmpDir,
                 (pure ? "" : "p=$PATH; "),
                 (pure ? "" : "PATH=$PATH:$p; unset p; "),
+                dirOf(shell),
+                shell,
                 (getenv("TZ") ? (string("export TZ='") + getenv("TZ") + "'; ") : ""),
                 envCommand));
 
diff --git a/src/nix-daemon/nix-daemon.cc b/src/nix-daemon/nix-daemon.cc
index 615c1f5dc065..423ba15e2ad0 100644
--- a/src/nix-daemon/nix-daemon.cc
+++ b/src/nix-daemon/nix-daemon.cc
@@ -709,7 +709,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         logger->startWork();
 
         // FIXME: race if addToStore doesn't read source?
-        store.cast<Store>()->addToStore(info, *source, (RepairFlag) repair,
+        store->addToStore(info, *source, (RepairFlag) repair,
             dontCheckSigs ? NoCheckSigs : CheckSigs, nullptr);
 
         logger->stopWork();
diff --git a/src/nix/copy.cc b/src/nix/copy.cc
index 91711c8b46da..96bd453d87b4 100644
--- a/src/nix/copy.cc
+++ b/src/nix/copy.cc
@@ -69,12 +69,12 @@ struct CmdCopy : StorePathsCommand
             },
 #ifdef ENABLE_S3
             Example{
-                "To populate the current folder build output to a S3 binary cache:",
-                "nix copy --to s3://my-bucket?region=eu-west-1"
+                "To copy Hello to an S3 binary cache:",
+                "nix copy --to s3://my-bucket?region=eu-west-1 nixpkgs.hello"
             },
             Example{
-                "To populate the current folder build output to an S3-compatible binary cache:",
-                "nix copy --to s3://my-bucket?region=eu-west-1&endpoint=example.com"
+                "To copy Hello to an S3-compatible binary cache:",
+                "nix copy --to s3://my-bucket?region=eu-west-1&endpoint=example.com nixpkgs.hello"
             },
 #endif
         };
diff --git a/src/nix/verify.cc b/src/nix/verify.cc
index 6540208a8a2c..7ef571561a0e 100644
--- a/src/nix/verify.cc
+++ b/src/nix/verify.cc
@@ -120,7 +120,7 @@ struct CmdVerify : StorePathsCommand
                             for (auto sig : sigs) {
                                 if (sigsSeen.count(sig)) continue;
                                 sigsSeen.insert(sig);
-                                if (info->checkSignature(publicKeys, sig))
+                                if (validSigs < ValidPathInfo::maxSigs && info->checkSignature(publicKeys, sig))
                                     validSigs++;
                             }
                         };
diff --git a/tests/build-remote.sh b/tests/build-remote.sh
index 9bca0f4a3856..ddd68f327a15 100644
--- a/tests/build-remote.sh
+++ b/tests/build-remote.sh
@@ -11,7 +11,8 @@ rm -rf $TEST_ROOT/store0 $TEST_ROOT/store1
 
 nix build -f build-hook.nix -o $TEST_ROOT/result --max-jobs 0 \
   --sandbox-paths /nix/store --sandbox-build-dir /build-tmp \
-  --builders "$TEST_ROOT/store0; $TEST_ROOT/store1 - - 1 1 foo"
+  --builders "$TEST_ROOT/store0; $TEST_ROOT/store1 - - 1 1 foo" \
+  --system-features foo
 
 outPath=$TEST_ROOT/result
 
diff --git a/tests/signing.sh b/tests/signing.sh
index 46929639199d..9e29e3fbf063 100644
--- a/tests/signing.sh
+++ b/tests/signing.sh
@@ -62,6 +62,10 @@ outPathCA=$(IMPURE_VAR1=foo IMPURE_VAR2=bar nix-build ./fixed.nix -A good.0 --no
 nix verify $outPathCA
 nix verify $outPathCA --sigs-needed 1000
 
+# Check that signing a content-addressed path doesn't overflow validSigs
+nix sign-paths --key-file $TEST_ROOT/sk1 $outPathCA
+nix verify -r $outPathCA --sigs-needed 1000 --trusted-public-keys $pk1
+
 # Copy to a binary cache.
 nix copy --to file://$cacheDir $outPath2