nixpkgs/nixos/doc/manual/man-nixos-version.xml

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<refmeta>
  <refentrytitle><command>nixos-version</command></refentrytitle>
  <manvolnum>8</manvolnum>
  <refmiscinfo class="source">NixOS</refmiscinfo>
</refmeta>

<refnamediv>
  <refname><command>nixos-version</command></refname>
  <refpurpose>show the NixOS version</refpurpose>
</refnamediv>

<refsynopsisdiv>
  <cmdsynopsis>
    <command>nixos-version</command>
    <arg><option>--hash</option></arg>
    <arg><option>--revision</option></arg>
  </cmdsynopsis>
</refsynopsisdiv>

<refsection><title>Description</title>

<para>This command shows the version of the currently active NixOS
configuration. For example:

<screen>$ nixos-version
16.03.1011.6317da4 (Emu)
</screen>

The version consists of the following elements:

<variablelist>

  <varlistentry>
    <term><literal>16.03</literal></term>
    <listitem><para>The NixOS release, indicating the year and month
    in which it was released (e.g. March 2016).</para></listitem>
  </varlistentry>

  <varlistentry>
    <term><literal>1011</literal></term>
    <listitem><para>The number of commits in the Nixpkgs Git
    repository between the start of the release branch and the commit
    from which this version was built. This ensures that NixOS
    versions are monotonically increasing. It is
    <literal>git</literal> when the current NixOS configuration was
    built from a checkout of the Nixpkgs Git repository rather than
    from a NixOS channel.</para></listitem>
  </varlistentry>

  <varlistentry>
    <term><literal>6317da4</literal></term>
    <listitem><para>The first 7 characters of the commit in the
    Nixpkgs Git repository from which this version was
    built.</para></listitem>
  </varlistentry>

  <varlistentry>
    <term><literal>Emu</literal></term>
    <listitem><para>The code name of the NixOS release. The first
    letter of the code name indicates that this is the N'th stable
    NixOS release; for example, Emu is the fifth
    release.</para></listitem>
  </varlistentry>

</variablelist>

</para>

</refsection>


<refsection><title>Options</title>

<para>This command accepts the following options:</para>

<variablelist>

  <varlistentry>
    <term><option>--hash</option></term>
    <term><option>--revision</option></term>
    <listitem>
      <para>Show the full SHA1 hash of the Git commit from which this
      configuration was built, e.g.
<screen>$ nixos-version --hash
6317da40006f6bc2480c6781999c52d88dde2acf
</screen>
      </para>
    </listitem>
  </varlistentry>
</variablelist>

</refsection>
</refentry>