man/systemd-homed.service.xml

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<refentry id="systemd-homed.service" conditional='ENABLE_HOMED'>

  <refentryinfo>
    <title>systemd-homed.service</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>systemd-homed.service</refentrytitle>
    <manvolnum>8</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>systemd-homed.service</refname>
    <refname>systemd-homed</refname>
    <refpurpose>Home Area/User Account Manager</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <para><filename>systemd-homed.service</filename></para>
    <para><filename>/usr/lib/systemd/systemd-homed</filename></para>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><command>systemd-homed</command> is a system service that may be used to create, remove, change or
    inspect home areas (directories and network mounts and real or loopback block devices with a filesystem,
    optionally encrypted).</para>

    <para>Most of <command>systemd-homed</command>'s functionality is accessible through the
    <citerefentry><refentrytitle>homectl</refentrytitle><manvolnum>1</manvolnum></citerefentry> command.</para>

    <para>See the <ulink url="https://systemd.io/HOME_DIRECTORY">Home Directories</ulink> documentation for
    details about the format and design of home areas managed by
    <filename>systemd-homed.service</filename>.</para>

    <para>Each home directory managed by <filename>systemd-homed.service</filename> synthesizes a local user
    and group. These are made available to the system using the <ulink
    url="https://systemd.io/USER_GROUP_API">User/Group Record Lookup API via Varlink</ulink>, and thus may be
    browsed with
    <citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para>
  </refsect1>

  <refsect1>
    <title>Key Management</title>

    <para>User records are cryptographically signed with a public/private key pair (the signature is part of
    the JSON record itself). For a user to be permitted to log in locally the public key matching the
    signature of their user record must be installed. For a user record to be modified locally the private
    key matching the signature must be installed locally, too. The keys are stored in the
    <filename>/var/lib/systemd/home/</filename> directory:</para>

    <variablelist>

      <varlistentry>
        <term><filename>/var/lib/systemd/home/local.private</filename></term>

        <listitem><para>The private key of the public/private key pair used for local records. Currently,
        only a single such key may be installed.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><filename>/var/lib/systemd/home/local.public</filename></term>

        <listitem><para>The public key of the public/private key pair used for local records. Currently,
        only a single such key may be installed.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><filename>/var/lib/systemd/home/*.public</filename></term>

        <listitem><para>Additional public keys. Any users whose user records are signed with any of these keys
        are permitted to log in locally. An arbitrary number of keys may be installed this
        way.</para></listitem>
      </varlistentry>
    </variablelist>

    <para>All key files listed above are in PEM format.</para>

    <para>In order to migrate a home directory from a host <literal>foobar</literal> to another host
    <literal>quux</literal> it is hence sufficient to copy
    <filename>/var/lib/systemd/home/local.public</filename> from the host <literal>foobar</literal> to
    <literal>quux</literal>, maybe calling the file on the destination <filename
    index="false">/var/lib/systemd/home/foobar.public</filename>, reflecting the origin of the key. If the
    user record should be modifiable on <literal>quux</literal> the pair
    <filename>/var/lib/systemd/home/local.public</filename> and
    <filename>/var/lib/systemd/home/local.private</filename> need to be copied from <literal>foobar</literal>
    to <literal>quux</literal>, and placed under the identical paths there, as currently only a single
    private key is supported per host. Note of course that the latter means that user records
    generated/signed before the key pair is copied in, lose their validity.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>homed.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>homectl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>pam_systemd_home</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>userdbctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>org.freedesktop.home1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    </para>
  </refsect1>
</refentry>