guix/doc/manual/nix-store.xml

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<refentry>
<refnamediv>
<refname>nix-store</refname>
<refpurpose>manipulate or query the Nix store</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>nix-store</command>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="opt-common-syn.xml#xpointer(/nop/*)" />
<arg choice='plain'><replaceable>operation</replaceable></arg>
<arg rep='repeat'><replaceable>options</replaceable></arg>
<arg rep='repeat'><replaceable>arguments</replaceable></arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsection>
<title>Description</title>
<para>
The command <command>nix-store</command> performs primitive
operations on the Nix store. You generally do not need to run
this command manually.
</para>
<para>
<command>nix-store</command> takes exactly one
<emphasis>operation</emphasis> flag which indicates the
subcommand to be performed. These are documented below.
</para>
</refsection>
<!--######################################################################-->
<refsection>
<title>Common options</title>
<para>
This section lists the options that are common to all
operations. These options are allowed for every subcommand,
though they may not always have an effect.
</para>
<variablelist>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="opt-common.xml#xpointer(/nop/*)" />
</variablelist>
</refsection>
<!--######################################################################-->
<refsection>
<title>Environment variables</title>
<para>
The following environment variables affect the behaviour of
<command>nix-store</command>.
</para>
<variablelist>
<varlistentry>
<term><envar>TMPDIR</envar>=<replaceable>path</replaceable></term>
<listitem>
<para>
Use the directory <replaceable>path</replaceable> to store
temporary files. In particular, this includes temporary
build directories; these can take up substantial amounts
of disk space. The default is <filename>/tmp</filename>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<!--######################################################################-->
<refsection id='rsec-nix-store-realise'>
<title>Operation <option>--realise</option></title>
<refsection>
<title>Synopsis</title>
<cmdsynopsis>
<command>nix-store</command>
<group choice='req'>
<arg choice='plain'><option>--realise</option></arg>
<arg choice='plain'><option>-r</option></arg>
</group>
<arg choice='plain' rep='repeat'><replaceable>paths</replaceable></arg>
</cmdsynopsis>
</refsection>
<refsection>
<title>Description</title>
<para>
The operation <option>--install</option> realises in the file
system the store expressions stored in
<replaceable>paths</replaceable>. If these expressions are
derivation expressions, they are first
<emphasis>normalised</emphasis> into a closure expression.
This may happen in two ways. First, the corresponding closure
expression (the <emphasis>successor</emphasis>) may already
known (either because the build has already been performed, or
because a successor was explicitly registered through the
<option>--successor</option> operation). Otherwise, the build
action described by the derivation is performed, and a closure
expression is computed by scanning the result of the build for
references to other paths in the store.
</para>
<para>
The paths of the closure expression corresponding to each
expression in <replaceable>paths</replaceable> is printed on
standard output.
</para>
</refsection>
</refsection>
<!--######################################################################-->
<refsection>
<title>Operation <option>--gc</option></title>
<refsection>
<title>Synopsis</title>
<cmdsynopsis>
<command>nix-store</command>
<arg choice='plain'><option>--gc</option></arg>
<group choice='req'>
<arg choice='plain'><option>--print-live</option></arg>
<arg choice='plain'><option>--print-dead</option></arg>
<arg choice='plain'><option>--delete</option></arg>
</group>
<arg><option>--min-age</option> <replaceable>age</replaceable></arg>
</cmdsynopsis>
</refsection>
<refsection>
<title>Description</title>
<para>
The operation <option>--gc</option> performs a garbage
collection on the Nix store. What it does specifically is
determined by the sub-operation, which is one of the
following:
</para>
<variablelist>
<varlistentry>
<term><option>--print-live</option></term>
<listitem>
<para>
This operation prints on standard output the set of
<quote>live</quote> store paths, which are all the store
paths reachable from a set of <quote>root</quote> store
expressions read from standard input. Live paths should
never be deleted, since that would break consistency —
it would become possible that applications are installed
that reference things that are no longer present in the
store.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--print-dead</option></term>
<listitem>
<para>
This operation prints out on standard output the set of
<quote>dead</quote> store paths, which is just the
opposite of the set of live paths: any path in the store
that is not live (with respect to the roots) is dead.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--delete</option></term>
<listitem>
<para>
This operation performs an actual garbage collection.
All dead paths are removed from the store.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
The set of root store expressions is read from standard input.
Each line should contain exactly one store path.
</para>
<para>
The option <option>--min-age</option> specifies a minimum time
in hours that an unreachable store path must not have been
used before it is considered dead. The default is 0 (consider
all unreachable store paths dead). Whether a store path has
been used is determined by looking at its access time
(<literal>atime</literal>), so this does not work if the store
is located on a file system that has the
<literal>noatime</literal> option set.
</para>
<warning>
<para>
You generally will want to use the command
<command>nix-collect-garbage</command>, which figures out
the roots and then calls this command automatically.
</para>
</warning>
</refsection>
</refsection>
<!--######################################################################-->
<refsection>
<title>Operation <option>--query</option></title>
<refsection>
<title>Synopsis</title>
<cmdsynopsis>
<command>nix-store</command>
<group choice='req'>
<arg choice='plain'><option>--query</option></arg>
<arg choice='plain'><option>-q</option></arg>
</group>
<group choice='req'>
<arg choice='plain'><option>--list</option></arg>
<arg choice='plain'><option>-l</option></arg>
<arg choice='plain'><option>--requisites</option></arg>
<arg choice='plain'><option>-R</option></arg>
<arg choice='plain'><option>--predecessors</option></arg>
<arg choice='plain'><option>--graph</option></arg>
</group>
<arg><option>--normalise</option></arg>
<arg><option>-n</option></arg>
<arg><option>--force-realise</option></arg>
<arg><option>-f</option></arg>
<arg choice='plain' rep='repeat'><replaceable>args</replaceable></arg>
</cmdsynopsis>
</refsection>
<refsection>
<title>Description</title>
<para>
The operation <option>--query</option> displays various bits
of information about store expressions or store paths. The
queries are described below. At most one query can be
specified. The default query is <option>--list</option>.
</para>
</refsection>
<refsection>
<title>Common query options</title>
<variablelist>
<varlistentry>
<term><option>--normalise</option> / <option>-n</option></term>
<listitem>
<para>
For those queries that take a Nix store expression, this
option causes those expressions to be normalised first.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--force-realise</option> / <option>-f</option></term>
<listitem>
<para>
For those queries that take a Nix store expression, this
option causes those expressions to be realised first.
This is just a short-cut for the common idiom
</para>
<screen>
nix-store --realise /nix/store/bla.store
x=`nix-store --query --normalise /nix/store/bla.store`
<emphasis>(do something with the path $x</emphasis></screen>
<para>
which using this flag can be written as
</para>
<screen>
x=`nix-store --query --normalise --force-realise /nix/store/bla.store`
<emphasis>(do something with the path $x</emphasis></screen>
</listitem>
</varlistentry>
</variablelist>
</refsection>
<refsection id='nixref-queries'>
<title>Queries</title>
<variablelist>
<varlistentry>
<term><option>--list</option> / <option>-l</option></term>
<listitem>
<para>
Prints out the <emphasis>output paths</emphasis> of the
store expressions indicated by the identifiers
<replaceable>args</replaceable>. In the case of a
derivation expression, these are the paths that will be
produced when the derivation is realised. In the case
of a closure expression, these are the paths that were
produced the derivation expression of which the closure
expression is a successor.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--requisites</option> / <option>-R</option></term>
<listitem>
<para>
Prints out the requisite paths of the store expressions
indicated by the identifiers
<replaceable>args</replaceable>. The requisite paths of
a Nix expression are the paths that need to be present
in the system to be able to realise the expression.
That is, they form the <emphasis>closure</emphasis> of
the expression in the file system (i.e., no path in the
set of requisite paths points to anything outside the
set of requisite paths).
</para>
<para>
The notion of requisite paths is very useful when one
wants to distribute store expressions. Since they form a
closure, they are the only paths one needs to distribute
to another system to be able to realise the expression
on the other system.
</para>
<para>
This query is generally used to implement various kinds
of deployment. A <emphasis>source deployment</emphasis>
is obtained by distributing the requisite paths of a
derivation expression. A <emphasis>binary
deployment</emphasis> is obtained by distributing the
requisite paths of a closure expression. A
<emphasis>cache deployment</emphasis> is obtained by
distributing the requisite paths of a derivation
expression and specifying the option
<option>--include-successors</option>. This will
include not just the paths of a source and binary
deployment, but also all expressions and paths of
subterms of the source. This is useful if one wants to
realise on the target system a Nix expression that is
similar but not quite the same as the one being
distributed, since any common subterms will be reused.
</para>
<para>
This query has a number of options:
</para>
<variablelist>
<varlistentry>
<term><option>--exclude-exprs</option></term>
<listitem>
<para>
Excludes the paths of store expressions. This
causes the closure property to be lost, that is,
the resulting set of paths is not enough to ensure
realisibility.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--include-successors</option></term>
<listitem>
<para>
Also include the requisites of successors (normal forms).
Only the requisites of <emphasis>known</emphasis>
successors are included, i.e., the normal forms of
derivation expressions that have never been normalised will
not be included.
</para>
<para>
Note that not just the successor of a derivation expression
will be included, but also the successors of all input
expressions of that derivation expression. I.e., all
normal forms of subterms involved in the normalisation of
the top-level term are included.
</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--predecessors</option></term>
<listitem>
<para>
For each store expression stored at paths
<replaceable>args</replaceable>, prints its
<emphasis>predecessors</emphasis>. A derivation
expression <varname>p</varname> is a predecessor of a
store expression <varname>q</varname> iff
<varname>q</varname> is a successor of
<varname>p</varname>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--graph</option></term>
<listitem>
<para>
Prints a graph of the closure of the store expressions
identified by <replaceable>args</replaceable> in the
format of the <command>dot</command> tool of AT&amp;T's
GraphViz package.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsection>
</refsection>
<!--######################################################################-->
<refsection>
<title>Operation <option>--successor</option></title>
<refsection>
<title>Synopsis</title>
<cmdsynopsis>
<command>nix-store</command>
<arg choice='req'><option>--successor</option></arg>
<arg choice='plain'
rep='repeat'><replaceable>srcpath</replaceable> <replaceable>sucpath</replaceable></arg>
</cmdsynopsis>
</refsection>
<refsection>
<title>Description</title>
<para>
The operation <option>--successor</option> registers that the
closure expression in <replaceable>sucpath</replaceable> is a
successor of the derivation expression in
<replaceable>srcpath</replaceable>. This is used to implement
binary deployment.
</para>
</refsection>
</refsection>
<!--######################################################################-->
<refsection>
<title>Operation <option>--substitute</option></title>
<refsection>
<title>Synopsis</title>
<cmdsynopsis>
<command>nix-store</command>
<arg choice='req'><option>--substitute</option></arg>
<arg choice='plain'
rep='repeat'><replaceable>srcpath</replaceable> <replaceable>subpath</replaceable></arg>
</cmdsynopsis>
</refsection>
<refsection>
<title>Description</title>
<para>
The operation <option>--substitute</option> registers that the
store path <replaceable>srcpath</replaceable> can be built by
realising the derivation expression in
<replaceable>subpath</replaceable>. This is used to implement
binary deployment.
</para>
</refsection>
</refsection>
<!--######################################################################-->
<refsection>
<title>Operation <option>--verify</option></title>
<refsection>
<title>Synopsis</title>
<cmdsynopsis>
<command>nix-store</command>
<arg choice='req'><option>--verify</option></arg>
</cmdsynopsis>
</refsection>
<refsection>
<title>Description</title>
<para>
The operation <option>--verify</option> verifies the internal
consistency of the Nix database, and the consistency between
the Nix database and the Nix store. Any inconsistencies
encountered are automatically repaired. Inconsistencies are
generally the result of the Nix store or database being
modified by non-Nix tools, or of bugs in Nix itself.
</para>
</refsection>
</refsection>
</refentry>
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