1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
<appendix xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Glossary</title>
<glosslist>
<glossentry xml:id="gloss-derivation"><glossterm>derivation</glossterm>
<glossdef><para>A description of a build action. The result of a
derivation is a store object. Derivations are typically specified
in Nix expressions using the <link
linkend="ssec-derivation"><function>derivation</function>
primitive</link>. These are translated into low-level
<emphasis>store derivations</emphasis> (implicitly by
<command>nix-env</command> and <command>nix-build</command>, or
explicitly by <command>nix-instantiate</command>).</para></glossdef>
</glossentry>
<glossentry><glossterm>store</glossterm>
<glossdef><para>The location in the file system where store objects
live. Typically <filename>/nix/store</filename>.</para></glossdef>
</glossentry>
<glossentry><glossterm>store path</glossterm>
<glossdef><para>The location in the file system of a store object,
i.e., an immediate child of the Nix store
directory.</para></glossdef>
</glossentry>
<glossentry><glossterm>store object</glossterm>
<glossdef><para>A file that is an immediate child of the Nix store
directory. These can be regular files, but also entire directory
trees. Store objects can be sources (objects copied from outside of
the store), derivation outputs (objects produced by running a build
action), or derivations (files describing a build
action).</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-substitute"><glossterm>substitute</glossterm>
<glossdef><para>A substitute is a command invocation stored in the
Nix database that describes how to build a store object, bypassing
the normal build mechanism (i.e., derivations). Typically, the
substitute builds the store object by downloading a pre-built
version of the store object from some server.</para></glossdef>
</glossentry>
<glossentry><glossterm>purity</glossterm>
<glossdef><para>The assumption that equal Nix derivations when run
always produce the same output. This cannot be guaranteed in
general (e.g., a builder can rely on external inputs such as the
network or the system time) but the Nix model assumes
it.</para></glossdef>
</glossentry>
<glossentry><glossterm>Nix expression</glossterm>
<glossdef><para>A high-level description of software packages and
compositions thereof. Deploying software using Nix entails writing
Nix expressions for your packages. Nix expressions are translated
to derivations that are stored in the Nix store. These derivations
can then be built.</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-reference"><glossterm>reference</glossterm>
<glossdef><para>A store path <varname>P</varname> is said to have a
reference to a store path <varname>Q</varname> if the store object
at <varname>P</varname> contains the path <varname>Q</varname>
somewhere. This implies than an execution involving
<varname>P</varname> potentially needs <varname>Q</varname> to be
present. The <emphasis>references</emphasis> of a store path are
the set of store paths to which it has a reference.</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-closure"><glossterm>closure</glossterm>
<glossdef><para>The closure of a store path is the set of store
paths that are directly or indirectly “reachable” from that store
path; that is, it’s the closure of the path under the <link
linkend="gloss-reference">references</link> relation. For instance,
if the store object at path <varname>P</varname> contains a
reference to path <varname>Q</varname>, then <varname>Q</varname> is
in the closure of <varname>P</varname>. For correct deployment it
is necessary to deploy whole closures, since otherwise at runtime
files could be missing. The command <command>nix-store
-qR</command> prints out closures of store paths.</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-output-path"><glossterm>output path</glossterm>
<glossdef><para>A store path produced by a derivation.</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-deriver"><glossterm>deriver</glossterm>
<glossdef><para>The deriver of an <link
linkend="gloss-output-path">output path</link> is the store
derivation that built it.</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-validity"><glossterm>validity</glossterm>
<glossdef><para>A store path is considered
<emphasis>valid</emphasis> if it exists in the file system, is
listed in the Nix database as being valid, and if all paths in its
closure are also valid.</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-user-env"><glossterm>user environment</glossterm>
<glossdef><para>An automatically generated store object that
consists of a set of symlinks to “active” applications, i.e., other
store paths. These are generated automatically by <link
linkend="sec-nix-env"><command>nix-env</command></link>. See <xref
linkend="sec-profiles" />.</para>
</glossdef>
</glossentry>
<glossentry xml:id="gloss-profile"><glossterm>profile</glossterm>
<glossdef><para>A symlink to the current <link
linkend="gloss-user-env">user environment</link> of a user, e.g.,
<filename>/nix/var/nix/profiles/default</filename>.</para></glossdef>
</glossentry>
<glossentry xml:id="gloss-nar"><glossterm>NAR</glossterm>
<glossdef><para>A <emphasis>N</emphasis>ix
<emphasis>AR</emphasis>chive. This is a serialisation of a path in
the Nix store. It can contain regular files, directories and
symbolic links. NARs are generated and unpacked using
<command>nix-store --dump</command> and <command>nix-store
--restore</command>.</para></glossdef>
</glossentry>
</glosslist>
</appendix>
|
