<para>The following OS identifications parameters may be set using
<filename>os-release</filename>:</para>
- <variablelist class='environment-variables'>
-
- <varlistentry>
- <term><varname>NAME=</varname></term>
-
- <listitem><para>A string identifying the operating system,
- without a version component, and suitable for presentation to
- the user. If not set, defaults to
- <literal>NAME=Linux</literal>. Example:
- <literal>NAME=Fedora</literal> or <literal>NAME="Debian
- GNU/Linux"</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>VERSION=</varname></term>
-
- <listitem><para>A string identifying the operating system
- version, excluding any OS name information, possibly including
- a release code name, and suitable for presentation to the
- user. This field is optional. Example:
- <literal>VERSION=17</literal> or <literal>VERSION="17 (Beefy
- Miracle)"</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>ID=</varname></term>
-
- <listitem><para>A lower-case string (no spaces or other
- characters outside of 0–9, a–z, ".", "_" and "-") identifying
- the operating system, excluding any version information and
- suitable for processing by scripts or usage in generated
- filenames. If not set, defaults to
- <literal>ID=linux</literal>. Example:
- <literal>ID=fedora</literal> or
- <literal>ID=debian</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>ID_LIKE=</varname></term>
-
- <listitem><para>A space-separated list of operating system
- identifiers in the same syntax as the <varname>ID=</varname>
- setting. It should list identifiers of operating systems that
- are closely related to the local operating system in regards
- to packaging and programming interfaces, for example listing
- one or more OS identifiers the local OS is a derivative from.
- An OS should generally only list other OS identifiers it
- itself is a derivative of, and not any OSes that are derived
- from it, though symmetric relationships are possible. Build
- scripts and similar should check this variable if they need to
- identify the local operating system and the value of
- <varname>ID=</varname> is not recognized. Operating systems
- should be listed in order of how closely the local operating
- system relates to the listed ones, starting with the closest.
- This field is optional. Example: for an operating system with
- <literal>ID=centos</literal>, an assignment of
- <literal>ID_LIKE="rhel fedora"</literal> would be appropriate.
- For an operating system with <literal>ID=ubuntu</literal>, an
- assignment of <literal>ID_LIKE=debian</literal> is
- appropriate.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>VERSION_CODENAME=</varname></term>
-
- <listitem><para>
- A lower-case string (no spaces or other characters outside of
- 0–9, a–z, ".", "_" and "-") identifying the operating system
- release code name, excluding any OS name information or
- release version, and suitable for processing by scripts or
- usage in generated filenames. This field is optional and may
- not be implemented on all systems.
- Examples:
- <literal>VERSION_CODENAME=buster</literal>,
- <literal>VERSION_CODENAME=xenial</literal>
- </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>VERSION_ID=</varname></term>
-
- <listitem><para>A lower-case string (mostly numeric, no spaces
- or other characters outside of 0–9, a–z, ".", "_" and "-")
- identifying the operating system version, excluding any OS
- name information or release code name, and suitable for
- processing by scripts or usage in generated filenames. This
- field is optional. Example: <literal>VERSION_ID=17</literal>
- or <literal>VERSION_ID=11.04</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>PRETTY_NAME=</varname></term>
-
- <listitem><para>A pretty operating system name in a format
- suitable for presentation to the user. May or may not contain
- a release code name or OS version of some kind, as suitable.
- If not set, defaults to
- <literal>PRETTY_NAME="Linux"</literal>. Example:
- <literal>PRETTY_NAME="Fedora 17 (Beefy
- Miracle)"</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>ANSI_COLOR=</varname></term>
-
- <listitem><para>A suggested presentation color when showing the OS name on the console. This should
- be specified as string suitable for inclusion in the ESC [ m ANSI/ECMA-48 escape code for setting
- graphical rendition. This field is optional. Example: <literal>ANSI_COLOR="0;31"</literal> for red,
- <literal>ANSI_COLOR="1;34"</literal> for light blue, or
- <literal>ANSI_COLOR="0;38;2;60;110;180"</literal> for Fedora blue.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>CPE_NAME=</varname></term>
-
- <listitem><para>A CPE name for the operating system, in URI
- binding syntax, following the
- <ulink url="http://scap.nist.gov/specifications/cpe/">Common
- Platform Enumeration Specification</ulink> as proposed by the
- NIST. This field is optional. Example:
- <literal>CPE_NAME="cpe:/o:fedoraproject:fedora:17"</literal>
- </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>HOME_URL=</varname></term>
- <term><varname>DOCUMENTATION_URL=</varname></term>
- <term><varname>SUPPORT_URL=</varname></term>
- <term><varname>BUG_REPORT_URL=</varname></term>
- <term><varname>PRIVACY_POLICY_URL=</varname></term>
-
- <listitem><para>Links to resources on the Internet related to
- the operating system.
- <varname>HOME_URL=</varname> should refer to the homepage of
- the operating system, or alternatively some homepage of the
- specific version of the operating system.
- <varname>DOCUMENTATION_URL=</varname> should refer to the main
- documentation page for this operating system.
- <varname>SUPPORT_URL=</varname> should refer to the main
- support page for the operating system, if there is any. This
- is primarily intended for operating systems which vendors
- provide support for. <varname>BUG_REPORT_URL=</varname> should
- refer to the main bug reporting page for the operating system,
- if there is any. This is primarily intended for operating
- systems that rely on community QA.
- <varname>PRIVACY_POLICY_URL=</varname> should refer to the
- main privacy policy page for the operating system, if there is
- any. These settings are optional, and providing only some of
- these settings is common. These URLs are intended to be
- exposed in "About this system" UIs behind links with captions
- such as "About this Operating System", "Obtain Support",
- "Report a Bug", or "Privacy Policy". The values should be in
- <ulink url="https://tools.ietf.org/html/rfc3986">RFC3986
- format</ulink>, and should be <literal>http:</literal> or
- <literal>https:</literal> URLs, and possibly
- <literal>mailto:</literal> or <literal>tel:</literal>. Only
- one URL shall be listed in each setting. If multiple resources
- need to be referenced, it is recommended to provide an online
- landing page linking all available resources. Examples:
- <literal>HOME_URL="https://fedoraproject.org/"</literal> and
- <literal>BUG_REPORT_URL="https://bugzilla.redhat.com/"</literal></para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>BUILD_ID=</varname></term>
-
- <listitem><para>A string uniquely identifying the system image
- used as the origin for a distribution (it is not updated with
- system updates). The field can be identical between different
- VERSION_IDs as BUILD_ID is an only a unique identifier to a
- specific version. Distributions that release each update as a
- new version would only need to use VERSION_ID as each build is
- already distinct based on the VERSION_ID. This field is
- optional. Example: <literal>BUILD_ID="2013-03-20.3"</literal>
- or <literal>BUILD_ID=201303203</literal>.
-
- </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>VARIANT=</varname></term>
-
- <listitem><para>
- A string identifying a specific variant or edition of the
- operating system suitable for presentation to the user. This
- field may be used to inform the user that the configuration of
- this system is subject to a specific divergent set of rules or
- default configuration settings. This field is optional and may
- not be implemented on all systems.
- Examples:
- <literal>VARIANT="Server Edition"</literal>,
- <literal>VARIANT="Smart Refrigerator Edition"</literal>
- Note: this field is for display purposes only. The
- <varname>VARIANT_ID</varname> field should be used for making
- programmatic decisions.
- </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>VARIANT_ID=</varname></term>
-
- <listitem><para>
- A lower-case string (no spaces or other characters outside of
- 0–9, a–z, ".", "_" and "-"), identifying a specific variant or
- edition of the operating system. This may be interpreted by
- other packages in order to determine a divergent default
- configuration. This field is optional and may not be
- implemented on all systems.
- Examples:
- <literal>VARIANT_ID=server</literal>,
- <literal>VARIANT_ID=embedded</literal>
- </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>LOGO=</varname></term>
-
- <listitem><para>
- A string, specifying the name of an icon as defined by <ulink
- url="http://standards.freedesktop.org/icon-theme-spec/latest">
- freedesktop.org Icon Theme Specification</ulink>. This can be
- used by graphical applications to display an operating
- system's or distributor's logo. This field is optional and
- may not necessarily be implemented on all systems.
- Examples:
- <literal>LOGO=fedora-logo</literal>,
- <literal>LOGO=distributor-logo-opensuse</literal>
- </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>DEFAULT_HOSTNAME=</varname></term>
-
- <listitem><para>A string specifying the hostname if
- <citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry> is not
- present and no other configuration source specifies the hostname. Must be either a single DNS label
- (a string composed of 7-bit ASCII lower-case characters and no spaces or dots, limited to the format
- allowed for DNS domain name labels), or a sequence of such labels separated by single dots that forms
- a valid DNS FQDN. The hostname must be at most 64 characters, which is a Linux limitation (DNS allows
- longer names).</para>
-
- <para>See
- <citerefentry><refentrytitle>org.freedesktop.hostname1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- for a description of how
- <citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
- determines the fallback hostname.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>SYSEXT_LEVEL=</varname></term>
-
- <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
- a–z, ".", "_" and "-") identifying the operating system extensions support level, to indicate which
- extension images are supported (See:
- <citerefentry><refentrytitle>systemd-sysext</refentrytitle><manvolnum>8</manvolnum></citerefentry>).
- Example: <literal>SYSEXT_LEVEL=2</literal> or
- <literal>SYSEXT_LEVEL=15.14</literal>.</para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>IMAGE_ID=</varname></term>
-
- <listitem><para> A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_" and
- "-"), identifying a specific image of the operating system. This is supposed to be used for
- environments where OS images are prepared, built, shipped and updated as comprehensive, consistent OS
- images. This field is optional and may not be implemented on all systems, in particularly not on those
- that are not managed via images but put together and updated from individual packages and on the
- local system. Examples: <literal>IMAGE_ID=vendorx-cashier-system</literal>,
- <literal>IMAGE_ID=netbook-image</literal> </para></listitem>
- </varlistentry>
-
- <varlistentry>
- <term><varname>IMAGE_VERSION=</varname></term>
-
- <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
- a–z, ".", "_" and "-") identifying the OS image version. This is supposed to be used together with
- <varname>IMAGE_ID</varname> described above, to discern different versions of the same
- image. Examples: <literal>IMAGE_VERSION=33</literal>,
- <literal>IMAGE_VERSION=47.1rc1</literal> </para></listitem>
- </varlistentry>
-
- </variablelist>
-
- <para>If you are reading this file from C code or a shell script
- to determine the OS or a specific version of it, use the
- <varname>ID</varname> and <varname>VERSION_ID</varname> fields,
- possibly with <varname>ID_LIKE</varname> as fallback for
- <varname>ID</varname>. When looking for an OS identification
- string for presentation to the user use the
- <varname>PRETTY_NAME</varname> field.</para>
-
- <para>Note that operating system vendors may choose not to provide
- version information, for example to accommodate for rolling
- releases. In this case, <varname>VERSION</varname> and
- <varname>VERSION_ID</varname> may be unset. Applications should
- not rely on these fields to be set.</para>
-
- <para>Operating system vendors may extend the file
- format and introduce new fields. It is highly
- recommended to prefix new fields with an OS specific
- name in order to avoid name clashes. Applications
- reading this file must ignore unknown fields. Example:
- <literal>DEBIAN_BTS="debbugs://bugs.debian.org/"</literal></para>
-
- <para>Container and sandbox runtime managers may make the host's
- identification data available to applications by providing the host's
- <filename>/etc/os-release</filename> (if available, otherwise
- <filename>/usr/lib/os-release</filename> as a fallback) as
- <filename>/run/host/os-release</filename>.</para>
+ <refsect2>
+ <title>General information identifying the operating system</title>
+
+ <variablelist class='environment-variables'>
+ <varlistentry>
+ <term><varname>NAME=</varname></term>
+
+ <listitem><para>A string identifying the operating system, without a version component, and
+ suitable for presentation to the user. If not set, a default of <literal>NAME=Linux</literal> may
+ be used.</para>
+
+ <para>Examples: <literal>NAME=Fedora</literal>, <literal>NAME="Debian GNU/Linux"</literal>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ID=</varname></term>
+
+ <listitem><para>A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_"
+ and "-") identifying the operating system, excluding any version information and suitable for
+ processing by scripts or usage in generated filenames. If not set, a default of
+ <literal>ID=linux</literal> may be used.</para>
+
+ <para>Examples: <literal>ID=fedora</literal>, <literal>ID=debian</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ID_LIKE=</varname></term>
+
+ <listitem><para>A space-separated list of operating system identifiers in the same syntax as the
+ <varname>ID=</varname> setting. It should list identifiers of operating systems that are closely
+ related to the local operating system in regards to packaging and programming interfaces, for
+ example listing one or more OS identifiers the local OS is a derivative from. An OS should
+ generally only list other OS identifiers it itself is a derivative of, and not any OSes that are
+ derived from it, though symmetric relationships are possible. Build scripts and similar should
+ check this variable if they need to identify the local operating system and the value of
+ <varname>ID=</varname> is not recognized. Operating systems should be listed in order of how
+ closely the local operating system relates to the listed ones, starting with the closest. This
+ field is optional.</para>
+
+ <para>Examples: for an operating system with <literal>ID=centos</literal>, an assignment of
+ <literal>ID_LIKE="rhel fedora"</literal> would be appropriate. For an operating system with
+ <literal>ID=ubuntu</literal>, an assignment of <literal>ID_LIKE=debian</literal> is appropriate.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>PRETTY_NAME=</varname></term>
+
+ <listitem><para>A pretty operating system name in a format suitable for presentation to the
+ user. May or may not contain a release code name or OS version of some kind, as suitable. If not
+ set, a default of <literal>PRETTY_NAME="Linux"</literal> may be used</para>
+
+ <para>Example: <literal>PRETTY_NAME="Fedora 17 (Beefy Miracle)"</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>CPE_NAME=</varname></term>
+
+ <listitem><para>A CPE name for the operating system, in URI binding syntax, following the <ulink
+ url="http://scap.nist.gov/specifications/cpe/">Common Platform Enumeration Specification</ulink> as
+ proposed by the NIST. This field is optional.</para>
+
+ <para>Example: <literal>CPE_NAME="cpe:/o:fedoraproject:fedora:17"</literal></para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>VARIANT=</varname></term>
+
+ <listitem><para>A string identifying a specific variant or edition of the operating system suitable
+ for presentation to the user. This field may be used to inform the user that the configuration of
+ this system is subject to a specific divergent set of rules or default configuration settings. This
+ field is optional and may not be implemented on all systems.</para>
+
+ <para>Examples: <literal>VARIANT="Server Edition"</literal>, <literal>VARIANT="Smart Refrigerator
+ Edition"</literal>.</para>
+
+ <para>Note: this field is for display purposes only. The <varname>VARIANT_ID</varname> field should
+ be used for making programmatic decisions.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>VARIANT_ID=</varname></term>
+
+ <listitem><para>A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_" and
+ "-"), identifying a specific variant or edition of the operating system. This may be interpreted by
+ other packages in order to determine a divergent default configuration. This field is optional and
+ may not be implemented on all systems.</para>
+
+ <para>Examples: <literal>VARIANT_ID=server</literal>, <literal>VARIANT_ID=embedded</literal>.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+
+ <refsect2>
+ <title>Information about the version of the operating system</title>
+
+ <variablelist class='environment-variables'>
+ <varlistentry>
+ <term><varname>VERSION=</varname></term>
+
+ <listitem><para>A string identifying the operating system version, excluding any OS name
+ information, possibly including a release code name, and suitable for presentation to the
+ user. This field is optional.</para>
+
+ <para>Examples: <literal>VERSION=17</literal>, <literal>VERSION="17 (Beefy Miracle)"</literal>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>VERSION_ID=</varname></term>
+
+ <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
+ a–z, ".", "_" and "-") identifying the operating system version, excluding any OS name information
+ or release code name, and suitable for processing by scripts or usage in generated filenames. This
+ field is optional.</para>
+
+ <para>Examples: <literal>VERSION_ID=17</literal>, <literal>VERSION_ID=11.04</literal>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>VERSION_CODENAME=</varname></term>
+
+ <listitem><para>A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_"
+ and "-") identifying the operating system release code name, excluding any OS name information or
+ release version, and suitable for processing by scripts or usage in generated filenames. This field
+ is optional and may not be implemented on all systems.</para>
+
+ <para>Examples: <literal>VERSION_CODENAME=buster</literal>,
+ <literal>VERSION_CODENAME=xenial</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>BUILD_ID=</varname></term>
+
+ <listitem><para>A string uniquely identifying the system image used as the origin for a distribution
+ (it is not updated with system updates). The field can be identical between different
+ <varname>VERSION_ID</varname>s as <varname>BUILD_ID</varname> is an only a unique identifier to a
+ specific version. Distributions that release each update as a new version would only need to use
+ <varname>VERSION_ID</varname> as each build is already distinct based on the
+ <varname>VERSION_ID</varname>. This field is optional.</para>
+
+ <para>Examples: <literal>BUILD_ID="2013-03-20.3"</literal>, <literal>BUILD_ID=201303203</literal>.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>IMAGE_ID=</varname></term>
+
+ <listitem><para> A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_"
+ and "-"), identifying a specific image of the operating system. This is supposed to be used for
+ environments where OS images are prepared, built, shipped and updated as comprehensive, consistent
+ OS images. This field is optional and may not be implemented on all systems, in particularly not on
+ those that are not managed via images but put together and updated from individual packages and on
+ the local system.</para>
+
+ <para>Examples: <literal>IMAGE_ID=vendorx-cashier-system</literal>,
+ <literal>IMAGE_ID=netbook-image</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>IMAGE_VERSION=</varname></term>
+
+ <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
+ a–z, ".", "_" and "-") identifying the OS image version. This is supposed to be used together with
+ <varname>IMAGE_ID</varname> described above, to discern different versions of the same image.
+ </para>
+
+ <para>Examples: <literal>IMAGE_VERSION=33</literal>, <literal>IMAGE_VERSION=47.1rc1</literal>.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+
+ <refsect2>
+ <title>Presentation information and links</title>
+
+ <variablelist class='environment-variables'>
+ <varlistentry>
+ <term><varname>HOME_URL=</varname></term>
+ <term><varname>DOCUMENTATION_URL=</varname></term>
+ <term><varname>SUPPORT_URL=</varname></term>
+ <term><varname>BUG_REPORT_URL=</varname></term>
+ <term><varname>PRIVACY_POLICY_URL=</varname></term>
+
+ <listitem><para>Links to resources on the Internet related to the operating system.
+ <varname>HOME_URL=</varname> should refer to the homepage of the operating system, or alternatively
+ some homepage of the specific version of the operating system.
+ <varname>DOCUMENTATION_URL=</varname> should refer to the main documentation page for this
+ operating system. <varname>SUPPORT_URL=</varname> should refer to the main support page for the
+ operating system, if there is any. This is primarily intended for operating systems which vendors
+ provide support for. <varname>BUG_REPORT_URL=</varname> should refer to the main bug reporting page
+ for the operating system, if there is any. This is primarily intended for operating systems that
+ rely on community QA. <varname>PRIVACY_POLICY_URL=</varname> should refer to the main privacy
+ policy page for the operating system, if there is any. These settings are optional, and providing
+ only some of these settings is common. These URLs are intended to be exposed in "About this system"
+ UIs behind links with captions such as "About this Operating System", "Obtain Support", "Report a
+ Bug", or "Privacy Policy". The values should be in <ulink
+ url="https://tools.ietf.org/html/rfc3986">RFC3986 format</ulink>, and should be
+ <literal>http:</literal> or <literal>https:</literal> URLs, and possibly <literal>mailto:</literal>
+ or <literal>tel:</literal>. Only one URL shall be listed in each setting. If multiple resources
+ need to be referenced, it is recommended to provide an online landing page linking all available
+ resources.</para>
+
+ <para>Examples: <literal>HOME_URL="https://fedoraproject.org/"</literal>,
+ <literal>BUG_REPORT_URL="https://bugzilla.redhat.com/"</literal>.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>LOGO=</varname></term>
+
+ <listitem><para>A string, specifying the name of an icon as defined by <ulink
+ url="http://standards.freedesktop.org/icon-theme-spec/latest">freedesktop.org Icon Theme
+ Specification</ulink>. This can be used by graphical applications to display an operating system's
+ or distributor's logo. This field is optional and may not necessarily be implemented on all
+ systems.</para>
+
+ <para>Examples: <literal>LOGO=fedora-logo</literal>, <literal>LOGO=distributor-logo-opensuse</literal>
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>ANSI_COLOR=</varname></term>
+
+ <listitem><para>A suggested presentation color when showing the OS name on the console. This should
+ be specified as string suitable for inclusion in the ESC [ m ANSI/ECMA-48 escape code for setting
+ graphical rendition. This field is optional.</para>
+
+ <para>Examples: <literal>ANSI_COLOR="0;31"</literal> for red, <literal>ANSI_COLOR="1;34"</literal>
+ for light blue, or <literal>ANSI_COLOR="0;38;2;60;110;180"</literal> for Fedora blue.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+
+ <refsect2>
+ <title>Distribution-level defaults and metadata</title>
+
+ <variablelist class='environment-variables'>
+ <varlistentry>
+ <term><varname>DEFAULT_HOSTNAME=</varname></term>
+
+ <listitem><para>A string specifying the hostname if
+ <citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry> is not
+ present and no other configuration source specifies the hostname. Must be either a single DNS label
+ (a string composed of 7-bit ASCII lower-case characters and no spaces or dots, limited to the
+ format allowed for DNS domain name labels), or a sequence of such labels separated by single dots
+ that forms a valid DNS FQDN. The hostname must be at most 64 characters, which is a Linux
+ limitation (DNS allows longer names).</para>
+
+ <para>See <citerefentry><refentrytitle>org.freedesktop.hostname1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ for a description of how
+ <citerefentry><refentrytitle>systemd-hostnamed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ determines the fallback hostname.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><varname>SYSEXT_LEVEL=</varname></term>
+
+ <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
+ a–z, ".", "_" and "-") identifying the operating system extensions support level, to indicate which
+ extension images are supported. See:
+ <citerefentry><refentrytitle>systemd-sysext</refentrytitle><manvolnum>8</manvolnum></citerefentry>)
+ for more information.</para>
+
+ <para>Examples: <literal>SYSEXT_LEVEL=2</literal>, <literal>SYSEXT_LEVEL=15.14</literal>.
+ </para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
+
+ <refsect2>
+ <title>Notes</title>
+
+ <para>If you are reading this file from C code or a shell script to determine the OS or a specific
+ version of it, use the <varname>ID</varname> and <varname>VERSION_ID</varname> fields, possibly with
+ <varname>ID_LIKE</varname> as fallback for <varname>ID</varname>. When looking for an OS identification
+ string for presentation to the user use the <varname>PRETTY_NAME</varname> field.</para>
+
+ <para>Note that operating system vendors may choose not to provide version information, for example to
+ accommodate for rolling releases. In this case, <varname>VERSION</varname> and
+ <varname>VERSION_ID</varname> may be unset. Applications should not rely on these fields to be
+ set.</para>
+
+ <para>Operating system vendors may extend the file format and introduce new fields. It is highly
+ recommended to prefix new fields with an OS specific name in order to avoid name clashes. Applications
+ reading this file must ignore unknown fields.</para>
+
+ <para>Example: <literal>DEBIAN_BTS="debbugs://bugs.debian.org/"</literal>.</para>
+
+ <para>Container and sandbox runtime managers may make the host's identification data available to
+ applications by providing the host's <filename>/etc/os-release</filename> (if available, otherwise
+ <filename>/usr/lib/os-release</filename> as a fallback) as
+ <filename>/run/host/os-release</filename>.</para>
+ </refsect2>
</refsect1>
<refsect1>
projects / thirdparty / systemd.git / commitdiff
