man/os-release.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   5
   6 <refentry id="os-release" xmlns:xi="http://www.w3.org/2001/XInclude">
   7   <refentryinfo>
   8     <title>os-release</title>
   9     <productname>systemd</productname>
  10   </refentryinfo>
  11
  12   <refmeta>
  13     <refentrytitle>os-release</refentrytitle>
  14     <manvolnum>5</manvolnum>
  15   </refmeta>
  16
  17   <refnamediv>
  18     <refname>os-release</refname>
  19     <refname>initrd-release</refname>
  20     <refname>extension-release</refname>
  21     <refpurpose>Operating system identification</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <para><filename>/etc/os-release</filename></para>
  26     <para><filename>/usr/lib/os-release</filename></para>
  27     <para><filename>/etc/initrd-release</filename></para>
  28     <para><filename>/usr/lib/extension-release.d/extension-release.<replaceable>IMAGE</replaceable></filename></para>
  29   </refsynopsisdiv>
  30
  31   <refsect1>
  32     <title>Description</title>
  33
  34     <para>The <filename>/etc/os-release</filename> and
  35     <filename>/usr/lib/os-release</filename> files contain operating
  36     system identification data.</para>
  37
  38     <para>The format of <filename>os-release</filename> is a newline-separated list of
  39     environment-like shell-compatible variable assignments. It is possible to source the configuration from
  40     Bourne shell scripts, however, beyond mere variable assignments, no shell features are supported (this
  41     means variable expansion is explicitly not supported), allowing applications to read the file without
  42     implementing a shell compatible execution engine. Variable assignment values must be enclosed in double
  43     or single quotes if they include spaces, semicolons or other special characters outside of A–Z, a–z,
  44     0–9. (Assignments that do not include these special characters may be enclosed in quotes too, but this is
  45     optional.) Shell special characters ("$", quotes, backslash, backtick) must be escaped with backslashes,
  46     following shell style. All strings should be in UTF-8 encoding, and non-printable characters should not
  47     be used. Concatenation of multiple individually quoted strings is not supported. Lines beginning with "#"
  48     are treated as comments. Blank lines are permitted and ignored.</para>
  49
  50     <para>The file <filename>/etc/os-release</filename> takes
  51     precedence over <filename>/usr/lib/os-release</filename>.
  52     Applications should check for the former, and exclusively use its
  53     data if it exists, and only fall back to
  54     <filename>/usr/lib/os-release</filename> if it is missing.
  55     Applications should not read data from both files at the same
  56     time. <filename>/usr/lib/os-release</filename> is the recommended
  57     place to store OS release information as part of vendor trees.
  58     <filename>/etc/os-release</filename> should be a relative symlink
  59     to <filename>/usr/lib/os-release</filename>, to provide
  60     compatibility with applications only looking at
  61     <filename>/etc/</filename>. A relative symlink instead of an
  62     absolute symlink is necessary to avoid breaking the link in a
  63     chroot or initrd environment such as dracut.</para>
  64
  65     <para><filename>os-release</filename> contains data that is
  66     defined by the operating system vendor and should generally not be
  67     changed by the administrator.</para>
  68
  69     <para>As this file only encodes names and identifiers it should
  70     not be localized.</para>
  71
  72     <para>The <filename>/etc/os-release</filename> and
  73     <filename>/usr/lib/os-release</filename> files might be symlinks
  74     to other files, but it is important that the file is available
  75     from earliest boot on, and hence must be located on the root file
  76     system.</para>
  77
  78     <para><filename>os-release</filename> must not contain repeating keys. Nevertheless, readers should pick
  79     the entries later in the file in case of repeats, similarly to how a shell sourcing the file would. A
  80     reader may warn about repeating entries.</para>
  81
  82     <para>For a longer rationale for <filename>os-release</filename>
  83     please refer to the <ulink
  84     url="http://0pointer.de/blog/projects/os-release">Announcement of <filename>/etc/os-release</filename></ulink>.</para>
  85
  86     <refsect2>
  87       <title><filename>/etc/initrd-release</filename></title>
  88
  89       <para>In the <ulink
  90       url="https://docs.kernel.org/admin-guide/initrd.html">initrd</ulink>,
  91       <filename>/etc/initrd-release</filename> plays the same role as <filename>os-release</filename> in the
  92       main system. Additionally, the presence of that file means that the system is in the initrd phase.
  93       <filename>/etc/os-release</filename> should be symlinked to <filename>/etc/initrd-release</filename>
  94       (or vice versa), so programs that only look for <filename>/etc/os-release</filename> (as described
  95       above) work correctly.</para>
  96
  97       <para>The rest of this document that talks about <filename>os-release</filename> should be understood
  98       to apply to <filename>initrd-release</filename> too.</para>
  99     </refsect2>
 100
 101     <refsect2>
 102       <title><filename>/usr/lib/extension-release.d/extension-release.<replaceable>IMAGE</replaceable></filename></title>
 103
 104       <para><filename>/usr/lib/extension-release.d/extension-release.<replaceable>IMAGE</replaceable></filename>
 105       plays the same role for extension images as <filename>os-release</filename> for the main system, and
 106       follows the syntax and rules as described in the <ulink
 107       url="https://systemd.io/PORTABLE_SERVICES">Portable Services Documentation</ulink>. The purpose of this
 108       file is to identify the extension and to allow the operating system to verify that the extension image
 109       matches the base OS. This is typically implemented by checking that the <varname>ID=</varname> options
 110       match, and either <varname>SYSEXT_LEVEL=</varname> exists and matches too, or if it is not present,
 111       <varname>VERSION_ID=</varname> exists and matches. This ensures ABI/API compatibility between the
 112       layers and prevents merging of an incompatible image in an overlay.</para>
 113
 114       <para>In the <filename>extension-release.<replaceable>IMAGE</replaceable></filename> filename, the
 115       <replaceable>IMAGE</replaceable> part must exactly match the file name of the containing image with the
 116       suffix removed. In case it is not possible to guarantee that an image file name is stable and doesn't
 117       change between the build and the deployment phases, it is possible to relax this check: if exactly one
 118       file whose name matches <literal><filename>extension-release.*</filename></literal> is present in this
 119       directory, and the file is tagged with a <varname>user.extension-release.strict</varname>
 120       <citerefentry project='man-pages'><refentrytitle>xattr</refentrytitle><manvolnum>7</manvolnum></citerefentry> set to the
 121       string <literal>0</literal>, it will be used instead.</para>
 122
 123       <para>The rest of this document that talks about <filename>os-release</filename> should be understood
 124       to apply to <filename>extension-release</filename> too.</para>
 125     </refsect2>
 126   </refsect1>
 127
 128   <refsect1>
 129     <title>Options</title>
 130
 131     <para>The following OS identifications parameters may be set using
 132     <filename>os-release</filename>:</para>
 133
 134     <refsect2>
 135       <title>General information identifying the operating system</title>
 136
 137       <variablelist class='environment-variables'>
 138         <varlistentry>
 139           <term><varname>NAME=</varname></term>
 140
 141           <listitem><para>A string identifying the operating system, without a version component, and
 142           suitable for presentation to the user. If not set, a default of <literal>NAME=Linux</literal> may
 143           be used.</para>
 144
 145           <para>Examples: <literal>NAME=Fedora</literal>, <literal>NAME="Debian GNU/Linux"</literal>.
 146           </para></listitem>
 147         </varlistentry>
 148
 149         <varlistentry>
 150           <term><varname>ID=</varname></term>
 151
 152           <listitem><para>A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_"
 153           and "-") identifying the operating system, excluding any version information and suitable for
 154           processing by scripts or usage in generated filenames. If not set, a default of
 155           <literal>ID=linux</literal> may be used. Note that even though this string may not include
 156           characters that require shell quoting, quoting may nevertheless be used.</para>
 157
 158           <para>Examples: <literal>ID=fedora</literal>, <literal>ID=debian</literal>.</para></listitem>
 159         </varlistentry>
 160
 161         <varlistentry>
 162           <term><varname>ID_LIKE=</varname></term>
 163
 164           <listitem><para>A space-separated list of operating system identifiers in the same syntax as the
 165           <varname>ID=</varname> setting. It should list identifiers of operating systems that are closely
 166           related to the local operating system in regards to packaging and programming interfaces, for
 167           example listing one or more OS identifiers the local OS is a derivative from.  An OS should
 168           generally only list other OS identifiers it itself is a derivative of, and not any OSes that are
 169           derived from it, though symmetric relationships are possible. Build scripts and similar should
 170           check this variable if they need to identify the local operating system and the value of
 171           <varname>ID=</varname> is not recognized. Operating systems should be listed in order of how
 172           closely the local operating system relates to the listed ones, starting with the closest. This
 173           field is optional.</para>
 174
 175           <para>Examples: for an operating system with <literal>ID=centos</literal>, an assignment of
 176           <literal>ID_LIKE="rhel fedora"</literal> would be appropriate. For an operating system with
 177           <literal>ID=ubuntu</literal>, an assignment of <literal>ID_LIKE=debian</literal> is appropriate.
 178           </para></listitem>
 179         </varlistentry>
 180
 181         <varlistentry>
 182           <term><varname>PRETTY_NAME=</varname></term>
 183
 184           <listitem><para>A pretty operating system name in a format suitable for presentation to the
 185           user. May or may not contain a release code name or OS version of some kind, as suitable. If not
 186           set, a default of <literal>PRETTY_NAME="Linux"</literal> may be used</para>
 187
 188           <para>Example: <literal>PRETTY_NAME="Fedora 17 (Beefy Miracle)"</literal>.</para></listitem>
 189         </varlistentry>
 190
 191         <varlistentry>
 192           <term><varname>CPE_NAME=</varname></term>
 193
 194           <listitem><para>A CPE name for the operating system, in URI binding syntax, following the <ulink
 195           url="http://scap.nist.gov/specifications/cpe/">Common Platform Enumeration Specification</ulink> as
 196           proposed by the NIST. This field is optional.</para>
 197
 198           <para>Example: <literal>CPE_NAME="cpe:/o:fedoraproject:fedora:17"</literal></para></listitem>
 199         </varlistentry>
 200
 201         <varlistentry>
 202           <term><varname>VARIANT=</varname></term>
 203
 204           <listitem><para>A string identifying a specific variant or edition of the operating system suitable
 205           for presentation to the user. This field may be used to inform the user that the configuration of
 206           this system is subject to a specific divergent set of rules or default configuration settings. This
 207           field is optional and may not be implemented on all systems.</para>
 208
 209           <para>Examples: <literal>VARIANT="Server Edition"</literal>, <literal>VARIANT="Smart Refrigerator
 210           Edition"</literal>.</para>
 211
 212           <para>Note: this field is for display purposes only. The <varname>VARIANT_ID</varname> field should
 213           be used for making programmatic decisions.</para></listitem>
 214         </varlistentry>
 215
 216         <varlistentry>
 217           <term><varname>VARIANT_ID=</varname></term>
 218
 219           <listitem><para>A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_" and
 220           "-"), identifying a specific variant or edition of the operating system. This may be interpreted by
 221           other packages in order to determine a divergent default configuration. This field is optional and
 222           may not be implemented on all systems.</para>
 223
 224           <para>Examples: <literal>VARIANT_ID=server</literal>, <literal>VARIANT_ID=embedded</literal>.
 225           </para></listitem>
 226         </varlistentry>
 227       </variablelist>
 228     </refsect2>
 229
 230     <refsect2>
 231       <title>Information about the version of the operating system</title>
 232
 233       <variablelist class='environment-variables'>
 234         <varlistentry>
 235           <term><varname>VERSION=</varname></term>
 236
 237           <listitem><para>A string identifying the operating system version, excluding any OS name
 238           information, possibly including a release code name, and suitable for presentation to the
 239           user. This field is optional.</para>
 240
 241           <para>Examples: <literal>VERSION=17</literal>, <literal>VERSION="17 (Beefy Miracle)"</literal>.
 242           </para></listitem>
 243         </varlistentry>
 244
 245         <varlistentry>
 246           <term><varname>VERSION_ID=</varname></term>
 247
 248           <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
 249           a–z, ".", "_" and "-") identifying the operating system version, excluding any OS name information
 250           or release code name, and suitable for processing by scripts or usage in generated filenames. This
 251           field is optional.</para>
 252
 253           <para>Examples: <literal>VERSION_ID=17</literal>, <literal>VERSION_ID=11.04</literal>.
 254           </para></listitem>
 255         </varlistentry>
 256
 257         <varlistentry>
 258           <term><varname>VERSION_CODENAME=</varname></term>
 259
 260           <listitem><para>A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_"
 261           and "-") identifying the operating system release code name, excluding any OS name information or
 262           release version, and suitable for processing by scripts or usage in generated filenames. This field
 263           is optional and may not be implemented on all systems.</para>
 264
 265           <para>Examples: <literal>VERSION_CODENAME=buster</literal>,
 266           <literal>VERSION_CODENAME=xenial</literal>.</para></listitem>
 267         </varlistentry>
 268
 269         <varlistentry>
 270           <term><varname>BUILD_ID=</varname></term>
 271
 272           <listitem><para>A string uniquely identifying the system image originally used as the installation
 273           base. In most cases, <varname>VERSION_ID</varname> or
 274           <varname>IMAGE_ID</varname>+<varname>IMAGE_VERSION</varname> are updated when the entire system
 275           image is replaced during an update. <varname>BUILD_ID</varname> may be used in distributions where
 276           the original installation image version is important: <varname>VERSION_ID</varname> would change
 277           during incremental system updates, but <varname>BUILD_ID</varname> would not. This field is
 278           optional.</para>
 279
 280           <para>Examples: <literal>BUILD_ID="2013-03-20.3"</literal>, <literal>BUILD_ID=201303203</literal>.
 281           </para></listitem>
 282         </varlistentry>
 283
 284         <varlistentry>
 285           <term><varname>IMAGE_ID=</varname></term>
 286
 287           <listitem><para> A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_"
 288           and "-"), identifying a specific image of the operating system. This is supposed to be used for
 289           environments where OS images are prepared, built, shipped and updated as comprehensive, consistent
 290           OS images. This field is optional and may not be implemented on all systems, in particularly not on
 291           those that are not managed via images but put together and updated from individual packages and on
 292           the local system.</para>
 293
 294           <para>Examples: <literal>IMAGE_ID=vendorx-cashier-system</literal>,
 295           <literal>IMAGE_ID=netbook-image</literal>.</para></listitem>
 296         </varlistentry>
 297
 298         <varlistentry>
 299           <term><varname>IMAGE_VERSION=</varname></term>
 300
 301           <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
 302           a–z, ".", "_" and "-") identifying the OS image version. This is supposed to be used together with
 303           <varname>IMAGE_ID</varname> described above, to discern different versions of the same image.
 304           </para>
 305
 306           <para>Examples: <literal>IMAGE_VERSION=33</literal>, <literal>IMAGE_VERSION=47.1rc1</literal>.
 307           </para></listitem>
 308         </varlistentry>
 309       </variablelist>
 310
 311       <para>To summarize: if the image updates are built and shipped as comprehensive units,
 312       <varname>IMAGE_ID</varname>+<varname>IMAGE_VERSION</varname> is the best fit. Otherwise, if updates
 313       eventually completely replace previously installed contents, as in a typical binary distribution,
 314       <varname>VERSION_ID</varname> should be used to identify major releases of the operating system.
 315       <varname>BUILD_ID</varname> may be used instead or in addition to <varname>VERSION_ID</varname> when
 316       the original system image version is important.</para>
 317     </refsect2>
 318
 319     <refsect2>
 320       <title>Presentation information and links</title>
 321
 322       <variablelist class='environment-variables'>
 323         <varlistentry>
 324           <term><varname>HOME_URL=</varname></term>
 325           <term><varname>DOCUMENTATION_URL=</varname></term>
 326           <term><varname>SUPPORT_URL=</varname></term>
 327           <term><varname>BUG_REPORT_URL=</varname></term>
 328           <term><varname>PRIVACY_POLICY_URL=</varname></term>
 329
 330           <listitem><para>Links to resources on the Internet related to the operating system.
 331           <varname>HOME_URL=</varname> should refer to the homepage of the operating system, or alternatively
 332           some homepage of the specific version of the operating system.
 333           <varname>DOCUMENTATION_URL=</varname> should refer to the main documentation page for this
 334           operating system.  <varname>SUPPORT_URL=</varname> should refer to the main support page for the
 335           operating system, if there is any. This is primarily intended for operating systems which vendors
 336           provide support for. <varname>BUG_REPORT_URL=</varname> should refer to the main bug reporting page
 337           for the operating system, if there is any. This is primarily intended for operating systems that
 338           rely on community QA. <varname>PRIVACY_POLICY_URL=</varname> should refer to the main privacy
 339           policy page for the operating system, if there is any. These settings are optional, and providing
 340           only some of these settings is common. These URLs are intended to be exposed in "About this system"
 341           UIs behind links with captions such as "About this Operating System", "Obtain Support", "Report a
 342           Bug", or "Privacy Policy". The values should be in <ulink
 343           url="https://tools.ietf.org/html/rfc3986">RFC3986 format</ulink>, and should be
 344           <literal>http:</literal> or <literal>https:</literal> URLs, and possibly <literal>mailto:</literal>
 345           or <literal>tel:</literal>. Only one URL shall be listed in each setting. If multiple resources
 346           need to be referenced, it is recommended to provide an online landing page linking all available
 347           resources.</para>
 348
 349           <para>Examples: <literal>HOME_URL="https://fedoraproject.org/"</literal>,
 350           <literal>BUG_REPORT_URL="https://bugzilla.redhat.com/"</literal>.</para></listitem>
 351         </varlistentry>
 352
 353         <varlistentry>
 354           <term><varname>SUPPORT_END=</varname></term>
 355
 356           <listitem><para>The date at which support for this version of the OS ends. (What exactly "lack of
 357           support" means varies between vendors, but generally users should assume that updates, including
 358           security fixes, will not be provided.) The value is a date in the ISO 8601 format
 359           <literal>YYYY-MM-DD</literal>, and specifies the first day on which support <emphasis>is
 360           not</emphasis> provided.</para>
 361
 362           <para>For example, <literal>SUPPORT_END=2001-01-01</literal> means that the system was supported
 363           until the end of the last day of the previous millennium.</para></listitem>
 364         </varlistentry>
 365
 366         <varlistentry>
 367           <term><varname>LOGO=</varname></term>
 368
 369           <listitem><para>A string, specifying the name of an icon as defined by <ulink
 370           url="https://standards.freedesktop.org/icon-theme-spec/latest">freedesktop.org Icon Theme
 371           Specification</ulink>. This can be used by graphical applications to display an operating system's
 372           or distributor's logo. This field is optional and may not necessarily be implemented on all
 373           systems.</para>
 374
 375           <para>Examples: <literal>LOGO=fedora-logo</literal>, <literal>LOGO=distributor-logo-opensuse</literal>
 376           </para></listitem>
 377         </varlistentry>
 378
 379         <varlistentry>
 380           <term><varname>ANSI_COLOR=</varname></term>
 381
 382           <listitem><para>A suggested presentation color when showing the OS name on the console. This should
 383           be specified as string suitable for inclusion in the ESC [ m ANSI/ECMA-48 escape code for setting
 384           graphical rendition. This field is optional.</para>
 385
 386           <para>Examples: <literal>ANSI_COLOR="0;31"</literal> for red, <literal>ANSI_COLOR="1;34"</literal>
 387           for light blue, or <literal>ANSI_COLOR="0;38;2;60;110;180"</literal> for Fedora blue.
 388           </para></listitem>
 389         </varlistentry>
 390       </variablelist>
 391     </refsect2>
 392
 393     <refsect2>
 394       <title>Distribution-level defaults and metadata</title>
 395
 396       <variablelist class='environment-variables'>
 397         <varlistentry>
 398           <term><varname>DEFAULT_HOSTNAME=</varname></term>
 399
 400           <listitem><para>A string specifying the hostname if
 401           <citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry> is not
 402           present and no other configuration source specifies the hostname. Must be either a single DNS label
 403           (a string composed of 7-bit ASCII lower-case characters and no spaces or dots, limited to the
 404           format allowed for DNS domain name labels), or a sequence of such labels separated by single dots
 405           that forms a valid DNS FQDN. The hostname must be at most 64 characters, which is a Linux
 406           limitation (DNS allows longer names).</para>
 407
 408           <para>See <citerefentry><refentrytitle>org.freedesktop.hostname1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 409           for a description of how
 410           <citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 411           determines the fallback hostname.</para></listitem>
 412         </varlistentry>
 413
 414         <varlistentry>
 415           <term><varname>ARCHITECTURE=</varname></term>
 416           <listitem><para>A string that specifies which CPU architecture the userspace binaries require.
 417           The architecture identifiers are the same as for <varname>ConditionArchitecture=</varname>
 418           described in <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
 419           The field is optional and should only be used when just single architecture is supported.
 420           It may provide redundant information when used in a GPT partition with a GUID type that already
 421           encodes the architecture. If this is not the case, the architecture should be specified in
 422           e.g., an extension image, to prevent an incompatible host from loading it.
 423           </para></listitem>
 424         </varlistentry>
 425
 426         <varlistentry>
 427           <term><varname>SYSEXT_LEVEL=</varname></term>
 428
 429           <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
 430           a–z, ".", "_" and "-") identifying the operating system extensions support level, to indicate which
 431           extension images are supported. See <filename>/usr/lib/extension-release.d/extension-release.<replaceable>IMAGE</replaceable></filename>,
 432           <ulink url="https://docs.kernel.org/admin-guide/initrd.html">initrd</ulink> and
 433           <citerefentry><refentrytitle>systemd-sysext</refentrytitle><manvolnum>8</manvolnum></citerefentry>)
 434           for more information.</para>
 435
 436           <para>Examples: <literal>SYSEXT_LEVEL=2</literal>, <literal>SYSEXT_LEVEL=15.14</literal>.
 437           </para></listitem>
 438         </varlistentry>
 439
 440         <varlistentry>
 441           <term><varname>SYSEXT_SCOPE=</varname></term>
 442           <listitem><para>Takes a space-separated list of one or more of the strings
 443           <literal>system</literal>, <literal>initrd</literal> and <literal>portable</literal>. This field is
 444           only supported in <filename>extension-release.d/</filename> files and indicates what environments
 445           the system extension is applicable to: i.e. to regular systems, to initrds, or to portable service
 446           images. If unspecified, <literal>SYSEXT_SCOPE=system portable</literal> is implied, i.e. any system
 447           extension without this field is applicable to regular systems and to portable service environments,
 448           but not to initrd environments.</para></listitem>
 449         </varlistentry>
 450
 451         <varlistentry>
 452           <term><varname>PORTABLE_PREFIXES=</varname></term>
 453           <listitem><para>Takes a space-separated list of one or more valid prefix match strings for the
 454           <ulink url="https://systemd.io/PORTABLE_SERVICES">Portable Services Documentation</ulink> logic.
 455           This field serves two purposes: it is informational, identifying portable service images as such
 456           (and thus allowing them to be distinguished from other OS images, such as bootable system images).
 457           It is also used when a portable service image is attached: the specified or implied portable
 458           service prefix is checked against the list specified here, to enforce restrictions how images may
 459           be attached to a system.</para></listitem>
 460         </varlistentry>
 461       </variablelist>
 462     </refsect2>
 463
 464     <refsect2>
 465       <title>Notes</title>
 466
 467       <para>If you are using this file to determine the OS or a specific version of it, use the
 468       <varname>ID</varname> and <varname>VERSION_ID</varname> fields, possibly with
 469       <varname>ID_LIKE</varname> as fallback for <varname>ID</varname>. When looking for an OS identification
 470       string for presentation to the user use the <varname>PRETTY_NAME</varname> field.</para>
 471
 472       <para>Note that operating system vendors may choose not to provide version information, for example to
 473       accommodate for rolling releases. In this case, <varname>VERSION</varname> and
 474       <varname>VERSION_ID</varname> may be unset. Applications should not rely on these fields to be
 475       set.</para>
 476
 477       <para>Operating system vendors may extend the file format and introduce new fields. It is highly
 478       recommended to prefix new fields with an OS specific name in order to avoid name clashes. Applications
 479       reading this file must ignore unknown fields.</para>
 480
 481       <para>Example: <literal>DEBIAN_BTS="debbugs://bugs.debian.org/"</literal>.</para>
 482
 483       <para>Container and sandbox runtime managers may make the host's identification data available to
 484       applications by providing the host's <filename>/etc/os-release</filename> (if available, otherwise
 485       <filename>/usr/lib/os-release</filename> as a fallback) as
 486       <filename>/run/host/os-release</filename>.</para>
 487     </refsect2>
 488   </refsect1>
 489
 490   <refsect1>
 491     <title>Examples</title>
 492
 493     <example>
 494       <title><filename>os-release</filename> file for Fedora Workstation</title>
 495
 496       <programlisting>NAME=Fedora
 497 VERSION="32 (Workstation Edition)"
 498 ID=fedora
 499 VERSION_ID=32
 500 PRETTY_NAME="Fedora 32 (Workstation Edition)"
 501 ANSI_COLOR="0;38;2;60;110;180"
 502 LOGO=fedora-logo-icon
 503 CPE_NAME="cpe:/o:fedoraproject:fedora:32"
 504 HOME_URL="https://fedoraproject.org/"
 505 DOCUMENTATION_URL="https://docs.fedoraproject.org/en-US/fedora/f32/system-administrators-guide/"
 506 SUPPORT_URL="https://fedoraproject.org/wiki/Communicating_and_getting_help"
 507 BUG_REPORT_URL="https://bugzilla.redhat.com/"
 508 REDHAT_BUGZILLA_PRODUCT="Fedora"
 509 REDHAT_BUGZILLA_PRODUCT_VERSION=32
 510 REDHAT_SUPPORT_PRODUCT="Fedora"
 511 REDHAT_SUPPORT_PRODUCT_VERSION=32
 512 PRIVACY_POLICY_URL="https://fedoraproject.org/wiki/Legal:PrivacyPolicy"
 513 VARIANT="Workstation Edition"
 514 VARIANT_ID=workstation</programlisting>
 515     </example>
 516
 517     <example>
 518       <title><filename>extension-release</filename> file for an extension for Fedora Workstation 32</title>
 519
 520       <programlisting>ID=fedora
 521 VERSION_ID=32</programlisting>
 522     </example>
 523
 524     <example>
 525       <title>Reading <filename>os-release</filename> in
 526       <citerefentry project='man-pages'><refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum></citerefentry></title>
 527
 528       <programlisting><xi:include href="check-os-release.sh" parse="text" /></programlisting>
 529     </example>
 530
 531     <example>
 532       <title>Reading <filename>os-release</filename> in
 533       <citerefentry project='die-net'><refentrytitle>python</refentrytitle><manvolnum>1</manvolnum></citerefentry> (versions &gt;= 3.10)</title>
 534
 535       <programlisting><xi:include href="check-os-release-simple.py" parse="text" /></programlisting>
 536
 537       <para>See docs for <ulink url="https://docs.python.org/3/library/platform.html#platform.freedesktop_os_release">
 538       <function>platform.freedesktop_os_release</function></ulink> for more details.
 539       </para>
 540     </example>
 541
 542     <example>
 543       <title>Reading <filename>os-release</filename> in
 544       <citerefentry project='die-net'><refentrytitle>python</refentrytitle><manvolnum>1</manvolnum></citerefentry> (any version)</title>
 545
 546       <programlisting><xi:include href="check-os-release.py" parse="text" /></programlisting>
 547
 548       <para>Note that the above version that uses the built-in implementation is preferred
 549       in most cases, and the open-coded version here is provided for reference.</para>
 550     </example>
 551
 552   </refsect1>
 553
 554   <refsect1>
 555       <title>See Also</title>
 556       <para>
 557         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 558         <citerefentry project='die-net'><refentrytitle>lsb_release</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 559         <citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 560         <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 561         <citerefentry><refentrytitle>machine-info</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 562       </para>
 563   </refsect1>
 564
 565 </refentry>