man: change recommended order of NSS modules in /etc/nsswitch.conf

So far we recommended placing "nss-mymachines" after "nss-resolve" in the order
of preference in /etc/nsswitch.conf. This change reverse this order.

Rationale: single-label names are resolved via LLMNR by resolved, which has to
time out if no peer by that name exists. By placing "nss-mymachines" first
(which always responds immediately) we avoid running into this timeout for most
containers. Both modules should return the same data if LLMNR is used by the
container anyway.

While we are at it, improve the man pages of the three NSS modules in other
ways a bit.

1 files changed, 19 insertions, 24 deletions

diff --git a/man/nss-mymachines.xml b/man/nss-mymachines.xml
index d2bec763bb..ec047449bf 100644
--- a/man/nss-mymachines.xml
+++ b/man/nss-mymachines.xml
@@ -56,42 +56,37 @@
   <refsect1>
     <title>Description</title>
 
-    <para><command>nss-mymachines</command> is a plugin for the GNU
-    Name Service Switch (NSS) functionality of the GNU C Library
-    (<command>glibc</command>), providing hostname resolution for
-    container names of containers running locally that are registered
-    with
-    <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
-    The container names are resolved to the IP addresses of the
-    specific container, ordered by their scope.</para>
-
-    <para>The module also resolves user IDs used by containers to user
-    names indicating the container name, and back.</para>
-
-    <para>To activate the NSS modules, <literal>mymachines</literal>
-    has to be added to the lines starting with
-    <literal>hosts:</literal>, <literal>passwd:</literal> and
-    <literal>group:</literal> in
+    <para><command>nss-mymachines</command> is a plug-in module for the GNU Name Service Switch (NSS) functionality of
+    the GNU C Library (<command>glibc</command>), providing hostname resolution for the names of containers running
+    locally that are registered with
+    <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.  The
+    container names are resolved to the IP addresses of the specific container, ordered by their scope. This
+    functionality only applies to containers using network namespacing.</para>
+
+    <para>The module also resolves user and group IDs used by containers to user and group names indicating the
+    container name, and back. This functionality only applies to containers using user namespacing.</para>
+
+    <para>To activate the NSS module, add <literal>mymachines</literal> to the lines starting with
+    <literal>hosts:</literal>, <literal>passwd:</literal> and <literal>group:</literal> in
     <filename>/etc/nsswitch.conf</filename>.</para>
 
-    <para>It is recommended to place <literal>mymachines</literal>
-    near the end of the <filename>nsswitch.conf</filename> lines to
-    make sure that its mappings are only used as fallback, and that any
-    other mappings, such as DNS or <filename>/etc/hosts</filename>
-    based mappings, take precedence.</para>
+    <para>It is recommended to place <literal>mymachines</literal> after the <literal>files</literal> or
+    <literal>compat</literal> entry of the <filename>/etc/nsswitch.conf</filename> lines to make sure that its mappings
+    are preferred over other resolvers such as DNS, but so that <filename>/etc/hosts</filename>,
+    <filename>/etc/passwd</filename> and <filename>/etc/group</filename> based mappings take precedence.</para>
   </refsect1>
 
   <refsect1>
     <title>Example</title>
 
-    <para>Here is an example <filename>/etc/nsswitch.conf</filename>
-    file that enables <command>mymachines</command> correctly:</para>
+    <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables
+    <command>nss-mymachines</command> correctly:</para>
 
     <programlisting>passwd:         compat <command>mymachines</command>
 group:          compat <command>mymachines</command>
 shadow:         compat
 
-hosts:          files resolve <command>mymachines</command> myhostname
+hosts:          files <command>mymachines</command> resolve myhostname
 networks:       files
 
 protocols:      db files