man: update documentation of slice units a bit

TODO

@@ -46,7 +46,7 @@ CGroup Rework Completion:
 * introduce high-level settings for RT budget, swappiness
 
 * wiki: document new bus APIs of PID 1 (transient units, Reloading signal)
-* review: slice units, systemctl commands
+* review: systemctl commands
 
 * Send SIGHUP and SIGTERM in session scopes
 

man/systemd.scope.xml

@@ -63,7 +63,7 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>.
     processes on its own.</para>
 
     <para>The main purpose of scope units is grouping worker processes
-    of a system service for organization and resource management.</para>
+    of a system service for organization and for managing resources.</para>
 
     <para><command>systemd-run <option>--scope</option></command> may
     be used to easily launch a command in a new scope unit from the

man/systemd.slice.xml

@@ -55,14 +55,34 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>.
     <title>Description</title>
 
     <para>A unit configuration file whose name ends in
-    <literal>.slice</literal> encodes information about a slice
+    <literal>.slice</literal> encodes information about a slice which
-    created by systemd to manage resources used by a certain group of
+    is a concept for hierarchially managing resources of a group of
     processes. This management is performed by creating a node in the
-    control group tree. Those processes are part of different units,
+    control group tree. Units that manage processes (primarilly scope
-    usually <literal>.service</literal> units (see
+    and service units) may be assigned to a specific slice. For each
-    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>).
+    slice certain resource limits may the be set, that apply to all
+    processes of all units contained in that slice. Slices are
+    organized hierarchially in a tree. The name of the slice encodes
+    the location in the tree. The name consists of a "-" separated
+    series of names, which describes the path to the slice from the
+    root slice. The root slice is named,
+    <filename>-.slice</filename>. Example:
+    <filename>foo-bar.slice</filename> is a slice that is located
+    within <filename>foo.slice</filename>, which in turn is located in
+    the root slice <filename>-.slice</filename>.
     </para>
 
+    <para>By default service and scope units are placed in
+    <filename>system.slice</filename>, virtual machines and containers
+    registered with
+    <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    are found in <filename>machine.slice</filename>, and user sessions
+    handled by
+    <citerefentry><refentrytitle>systemd-logind</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    in <filename>user.slice</filename>. See
+    <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+    for more information.</para>
+
     <para>See
     <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>
     for the common options of all unit configuration
@@ -92,7 +112,9 @@ along with systemd; If not, see <http://www.gnu.org/licenses/>.
       <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd.cgroup</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
-      <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+      <citerefentry><refentrytitle>systemd.scope</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd.special</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
     </para>
   </refsect1>