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diff --git a/doc/manual/nix-push.xml b/doc/manual/nix-push.xml new file mode 100644 index 000000000000..e789bbf7d352 --- /dev/null +++ b/doc/manual/nix-push.xml @@ -0,0 +1,398 @@ +<refentry xmlns="http://docbook.org/ns/docbook" + xmlns:xlink="http://www.w3.org/1999/xlink" + xmlns:xi="http://www.w3.org/2001/XInclude" + xml:id="sec-nix-push"> + +<refmeta> + <refentrytitle>nix-push</refentrytitle> + <manvolnum>1</manvolnum> + <refmiscinfo class="source">Nix</refmiscinfo> + <refmiscinfo class="version"><xi:include href="version.txt" parse="text"/></refmiscinfo> +</refmeta> + +<refnamediv> + <refname>nix-push</refname> + <refpurpose>generate a binary cache</refpurpose> +</refnamediv> + +<refsynopsisdiv> + <cmdsynopsis> + <command>nix-push</command> + <arg choice='plain'><option>--dest</option> <replaceable>dest-dir</replaceable></arg> + <arg><option>--bzip2</option></arg> + <arg><option>--none</option></arg> + <arg><option>--force</option></arg> + <arg><option>--link</option></arg> + <arg><option>--manifest</option></arg> + <arg><option>--manifest-path</option> <replaceable>filename</replaceable></arg> + <arg><option>--url-prefix</option> <replaceable>url</replaceable></arg> + <arg choice='plain' rep='repeat'><replaceable>paths</replaceable></arg> + </cmdsynopsis> +</refsynopsisdiv> + + +<refsection><title>Description</title> + +<para>The command <command>nix-push</command> produces a +<emphasis>binary cache</emphasis>, a directory containing compressed +Nix archives (NARs) plus some metadata of the closure of the specified +store paths. This directory can then be made available through a web +server to other Nix installations, allowing them to skip building from +source and instead download binaries from the cache +automatically.</para> + +<para><command>nix-push</command> performs the following actions. + +<orderedlist> + + <listitem><para>Each path in <replaceable>paths</replaceable> is + built (using <link + linkend='rsec-nix-store-realise'><command>nix-store + --realise</command></link>).</para></listitem> + + <listitem><para>All paths in the closure of + <replaceable>paths</replaceable> are determined (using + <command>nix-store --query --requisites + --include-outputs</command>). Note that since the + <option>--include-outputs</option> flag is used, if + <replaceable>paths</replaceable> includes a store derivation, you + get a combined source/binary distribution (e.g., source tarballs + will be included).</para></listitem> + + <listitem><para>All store paths determined in the previous step are + packaged into a NAR (using <command>nix-store --dump</command>) and + compressed using <command>xz</command> or <command>bzip2</command>. + The resulting files have the extension <filename>.nar.xz</filename> + or <filename>.nar.bz2</filename>. Also for each store path, Nix + generates a file with extension <filename>.narinfo</filename> + containing metadata such as the references, cryptographic hash and + size of each path.</para></listitem> + + <listitem><para>Optionally, a single <emphasis>manifest</emphasis> + file is created that contains the same metadata as the + <filename>.narinfo</filename> files. This is for compatibility with + Nix versions prior to 1.2 (see <command>nix-pull</command> for + details).</para></listitem> + + <listitem><para>A file named <option>nix-cache-info</option> is + placed in the destination directory. The existence of this file + marks the directory as a binary cache.</para></listitem> + +</orderedlist> + +</para> + +</refsection> + + +<refsection><title>Options</title> + +<variablelist> + + <varlistentry><term><option>--dest</option> <replaceable>dest-dir</replaceable></term> + + <listitem><para>Set the destination directory to + <replaceable>dir</replaceable>, which is created if it does not + exist. This flag is required.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--bzip2</option></term> + + <listitem><para>Compress NARs using <command>bzip2</command> + instead of <command>xz -9</command>. The latter compresses about + 30% better on typical archives, decompresses about twice as fast, + but compresses a lot slower and is not supported by Nix prior to + version 1.2.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--none</option></term> + + <listitem><para>Do not compress NARs.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--force</option></term> + + <listitem><para>Overwrite <filename>.narinfo</filename> files if + they already exist.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--link</option></term> + + <listitem><para>By default, NARs are generated in the Nix store + and then copied to <replaceable>dest-dir</replaceable>. If this + option is given, hard links are used instead. This only works if + <replaceable>dest-dir</replaceable> is on the same filesystem as + the Nix store.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--manifest</option></term> + + <listitem><para>Force the generation of a manifest suitable for + use by <command>nix-pull</command>. The manifest is stored as + <filename><replaceable>dest-dir</replaceable>/MANIFEST</filename>.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--manifest-path</option> <replaceable>filename</replaceable></term> + + <listitem><para>Like <option>--manifest</option>, but store the + manifest in <replaceable>filename</replaceable>.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--url-prefix</option> <replaceable>url</replaceable></term> + + <listitem><para>Manifests are expected to contain the absolute + URLs of NARs. For generating these URLs, the prefix + <replaceable>url</replaceable> is used. It defaults to + <uri>file://<replaceable>dest-dir</replaceable></uri>.</para></listitem> + + </varlistentry> + +</variablelist> + +</refsection> + + +<refsection><title>Examples</title> + +<para>To add the closure of Thunderbird to a binary cache: + +<screen> +$ nix-push --dest /tmp/cache $(nix-build -A thunderbird) +</screen> + +Assuming that <filename>/tmp/cache</filename> is exported by a web +server as <uri>http://example.org/cache</uri>, you can then use this +cache on another machine to speed up the installation of Thunderbird: + +<screen> +$ nix-build -A thunderbird --option binary-caches http://example.org/cache +</screen> + +Alternatively, you could add <literal>binary-caches = +http://example.org/cache</literal> to +<filename>nix.conf</filename>.</para> + +<para>To also include build-time dependencies (such as source +tarballs): + +<screen> +$ nix-push --dest /tmp/cache $(nix-instantiate -A thunderbird) +</screen> + +</para> + +<para>To generate a manifest suitable for <command>nix-pull</command>: + +<screen> +$ nix-push --dest /tmp/cache $(nix-build -A thunderbird) --manifest +</screen> + +On another machine you can then do: + +<screen> +$ nix-pull http://example.org/cache +</screen> + +to cause the binaries to be used by subsequent Nix operations.</para> + +</refsection> + + +<refsection><title>Binary cache format and operation</title> + +<para>A binary cache with URL <replaceable>url</replaceable> only +denotes a valid binary cache if the file +<uri><replaceable>url</replaceable>/nix-cache-info</uri> exists. If +this file does not exist (or cannot be downloaded), the cache is +ignored. If it does exist, it must be a text file containing cache +properties. Here’s an example: + +<screen> +StoreDir: /nix/store +WantMassQuery: 1 +Priority: 10 +</screen> + +The properties that are currently supported are: + +<variablelist> + + <varlistentry><term><literal>StoreDir</literal></term> + + <listitem><para>The path of the Nix store to which this binary + cache applies. Binaries are not relocatable — a binary built for + <filename>/nix/store</filename> won’t generally work in + <filename>/home/alice/store</filename> — so to prevent binaries + from being used in a wrong store, a binary cache is only used if + its <literal>StoreDir</literal> matches the local Nix + configuration. The default is + <filename>/nix/store</filename>.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>WantMassQuery</literal></term> + + <listitem><para>Query operations such as <command>nix-env + -qas</command> can cause thousands of cache queries, and thus + thousands of HTTP requests, to determine which packages are + available in binary form. While these requests are small, not + every server may appreciate a potential onslaught of queries. If + <literal>WantMassQuery</literal> is set to <literal>0</literal> + (default), “mass queries” such as <command>nix-env -qas</command> + will skip this cache. Thus a package may appear not to have a + binary substitute. However, the binary will still be used when + you actually install the package. If + <literal>WantMassQuery</literal> is set to <literal>1</literal>, + mass queries will use this cache.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>Priority</literal></term> + + <listitem><para>Each binary cache has a priority (defaulting to + 50). Binary caches are checked for binaries in order of ascending + priority; thus a higher number denotes a lower priority. The + binary cache <uri>http://cache.nixos.org</uri> has priority + 40.</para></listitem> + + </varlistentry> + +</variablelist> + +</para> + +<para>Every time Nix needs to build some store path +<replaceable>p</replaceable>, it will check each configured binary +cache to see if it has a NAR file for <replaceable>p</replaceable>, +until it finds one. If no cache has a NAR, Nix will fall back to +building the path from source (if applicable). To see if a cache with +URL <replaceable>url</replaceable> has a binary for +<replaceable>p</replaceable>, Nix fetches +<replaceable>url/h</replaceable>, where <replaceable>h</replaceable> +is the hash part of <replaceable>p</replaceable>. Thus, if we have a +cache <uri>http://cache.nixos.org</uri> and we want to obtain +the store path +<screen> +/nix/store/a8922c0h87iilxzzvwn2hmv8x210aqb9-glibc-2.7 +</screen> +then Nix will attempt to fetch +<screen> +http://cache.nixos.org/a8922c0h87iilxzzvwn2hmv8x210aqb9.narinfo +</screen> +(Commands such as <command>nix-env -qas</command> will issue an HTTP +HEAD request, since it only needs to know if the +<filename>.narinfo</filename> file exists.) The +<filename>.narinfo</filename> file is a simple text file that looks +like this: + +<screen> +StorePath: /nix/store/a8922c0h87iilxzzvwn2hmv8x210aqb9-glibc-2.7 +URL: nar/0zzjpdz46mdn74v09m053yczlz4am038g8r74iy8w43gx8801h70.nar.bz2 +Compression: bzip2 +FileHash: sha256:0zzjpdz46mdn74v09m053yczlz4am038g8r74iy8w43gx8801h70 +FileSize: 24473768 +NarHash: sha256:0s491y1h9hxj5ghiizlxk7ax6jwbha00zwn7lpyd5xg5bhf60vzg +NarSize: 109521136 +References: 2ma2k0ys8knh4an48n28vigcmc2z8773-linux-headers-2.6.23.16 ... +Deriver: 7akyyc87ka32xwmqza9dvyg5pwx3j212-glibc-2.7.drv +</screen> + +The fields are as follows: + +<variablelist> + + <varlistentry><term><literal>StorePath</literal></term> + + <listitem><para>The full store path, including the name part + (e.g., <literal>glibc-2.7</literal>). It must match the + requested store path.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>URL</literal></term> + + <listitem><para>The URL of the NAR, relative to the binary cache + URL.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>Compression</literal></term> + + <listitem><para>The compression method; either + <literal>xz</literal> or + <literal>bzip2</literal>.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>FileHash</literal></term> + + <listitem><para>The SHA-256 hash of the compressed + NAR.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>FileSize</literal></term> + + <listitem><para>The size of the compressed NAR.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>NarHash</literal></term> + + <listitem><para>The SHA-256 hash of the uncompressed NAR. This is + equal to the hash of the store path as returned by + <command>nix-store -q --hash + <replaceable>p</replaceable></command>.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>NarSize</literal></term> + + <listitem><para>The size of the uncompressed NAR.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>References</literal></term> + + <listitem><para>The references of the store path, without the Nix + store prefix.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>Deriver</literal></term> + + <listitem><para>The deriver of the store path, without the Nix + store prefix. This field is optional.</para></listitem> + + </varlistentry> + + <varlistentry><term><literal>System</literal></term> + + <listitem><para>The Nix platform type of this binary, if known. + This field is optional.</para></listitem> + + </varlistentry> + +</variablelist> + +</para> + +<para>Thus, in our example, after recursively ensuring that the +references exist (e.g., +<filename>/nix/store/2ma2k0ys8knh4an48n28vigcmc2z8773-linux-headers-2.6.23.16</filename>), +Nix will fetch <screen> +http://cache.nixos.org/nar/0zzjpdz46mdn74v09m053yczlz4am038g8r74iy8w43gx8801h70.nar.bz2 +</screen> and decompress and unpack it to +<filename>/nix/store/a8922c0h87iilxzzvwn2hmv8x210aqb9-glibc-2.7</filename>.</para> + +</refsection> + + +</refentry> |