man: document that some unit types do not support unit aliases via symlinks

man/systemd.automount.xml

@@ -66,14 +66,13 @@
     [Install] sections. The automount specific configuration options
     are configured in the [Automount] section.</para>
 
-    <para>Automount units must be named after the automount
+    <para>Automount units must be named after the automount directories they control. Example: the automount point
-    directories they control. Example: the automount point
+    <filename noindex='true'>/home/lennart</filename> must be configured in a unit file
-    <filename noindex='true'>/home/lennart</filename> must be
+    <filename>home-lennart.automount</filename>. For details about the escaping logic used to convert a file system
-    configured in a unit file
+    path to a unit name see
-    <filename>home-lennart.automount</filename>. For details about the
+    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Note that
-    escaping logic used to convert a file system path to a unit name
+    automount units cannot be templated, nor is it possible to add multiple names to an automount unit by creating
-    see
+    additional symlinks to its unit file.</para>
-    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 
     <para>For each automount unit file a matching mount unit file (see
     <citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>

man/systemd.mount.xml

@@ -82,14 +82,12 @@
     will refuse options that are not listed in
     <filename>/etc/fstab</filename> if it is not run as UID 0.</para>
 
-    <para>Mount units must be named after the mount point directories
+    <para>Mount units must be named after the mount point directories they control. Example: the mount point <filename
-    they control. Example: the mount point
+    noindex='true'>/home/lennart</filename> must be configured in a unit file <filename>home-lennart.mount</filename>.
-    <filename noindex='true'>/home/lennart</filename> must be
+    For details about the escaping logic used to convert a file system path to a unit name, see
-    configured in a unit file <filename>home-lennart.mount</filename>.
+    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.  Note that mount
-    For details about the escaping logic used to convert a file system
+    units cannot be templated, nor is possible to add multiple names to a mount unit by creating additional symlinks to
-    path to a unit name, see
+    it.</para>
-    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.
-    Note that mount units cannot be templated.</para>
 
     <para>Optionally, a mount unit may be accompanied by an automount
     unit, to allow on-demand or parallelized mounting. See

man/systemd.slice.xml

@@ -71,6 +71,9 @@
     the root slice <filename>-.slice</filename>.
     </para>
 
+    <para>Note that slice units cannot be templated, nor is possible to add multiple names to a slice unit by creating
+    additional symlinks to it.</para>
+
     <para>By default, service and scope units are placed in
     <filename>system.slice</filename>, virtual machines and containers
     registered with

man/systemd.swap.xml

@@ -78,13 +78,12 @@
     which configure resource control settings for these processes of the
     unit.</para>
 
-    <para>Swap units must be named after the devices
+    <para>Swap units must be named after the devices or files they control. Example: the swap device <filename
-    or files they control. Example: the swap device
+    noindex='true'>/dev/sda5</filename> must be configured in a unit file <filename>dev-sda5.swap</filename>. For
-    <filename noindex='true'>/dev/sda5</filename> must be configured in a
+    details about the escaping logic used to convert a file system path to a unit name, see
-    unit file <filename>dev-sda5.swap</filename>. For details about
+    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>. Note that swap
-    the escaping logic used to convert a file system path to a unit
+    units cannot be templated, nor is possible to add multiple names to a swap unit by creating additional symlinks to
-    name, see
+    it.</para>
-    <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
   </refsect1>
 
   <refsect1>

man/systemd.unit.xml

@@ -1102,13 +1102,12 @@
       <varlistentry>
         <term><varname>Alias=</varname></term>
 
-        <listitem><para>A space-separated list of additional names
+        <listitem><para>A space-separated list of additional names this unit shall be installed under. The names listed
-        this unit shall be installed under. The names listed here must
+        here must have the same suffix (i.e. type) as the unit file name. This option may be specified more than once,
-        have the same suffix (i.e. type) as the unit file name. This
+        in which case all listed names are used. At installation time, <command>systemctl enable</command> will create
-        option may be specified more than once, in which case all
+        symlinks from these names to the unit filename. Note that not all unit types support such alias names, and this
-        listed names are used. At installation time,
+        setting is not supported for them. Specifically, mount, slice, swap, and automount units do not support
-        <command>systemctl enable</command> will create symlinks from
+        aliasing.</para></listitem>
-        these names to the unit filename.</para></listitem>
       </varlistentry>
 
       <varlistentry>