- <para>systemd will dynamically create device units for all kernel
- devices that are marked with the "systemd" udev tag (by default
- all block and network devices, and a few others). This may be used
- to define dependencies between devices and other units. To tag a
- udev device, use <literal>TAG+="systemd"</literal> in the udev
- rules file, see
- <citerefentry><refentrytitle>udev</refentrytitle><manvolnum>7</manvolnum></citerefentry>
- for details.</para>
-
- <para>Device units are named after the <filename>/sys</filename>
- and <filename>/dev</filename> paths they control. Example: the
- device <filename noindex='true'>/dev/sda5</filename> is exposed in
+ <para>systemd will dynamically create device units for all kernel devices that are marked with the
+ <literal>systemd</literal> udev tag (by default all block and network devices, and a few others). Note
+ that <emphasis>if <filename>systemd-udevd.service</filename> is not running, no device units will be
+ available (for example in a typical container)</emphasis>.</para>
+
+ <para>Device units are named after the <filename>/sys/</filename>
+ and <filename>/dev/</filename> paths they control. Example: the
+ device <filename index="false">/dev/sda5</filename> is exposed in