From 9f0840e421c3fc5df404ad51dd37e5ebb13f288b Mon Sep 17 00:00:00 2001
From: =?utf8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Thu, 25 Feb 2021 14:14:39 +0100
Subject: [PATCH] man: say that hostname must can be a fqdn or not

Fixes #18426
---
 man/hostnamectl.xml | 15 +++++++++++----
 man/os-release.xml  |  3 ++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/man/hostnamectl.xml b/man/hostnamectl.xml
index 224dab78a7c..8be8972907c 100644
--- a/man/hostnamectl.xml
+++ b/man/hostnamectl.xml
@@ -1,6 +1,9 @@
 <?xml version='1.0'?> <!--*-nxml-*-->
 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
-  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
+<!ENTITY % entities SYSTEM "custom-entities.ent" >
+%entities;
+]>
 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
 
 <refentry id="hostnamectl" conditional='ENABLE_HOSTNAMED'
@@ -76,9 +79,13 @@
         still following the validity rules of the specific name. This simplification of the hostname string is not done
         if only the transient and/or static hostnames are set, and the pretty hostname is left untouched.</para>
 
-        <para>Pass the empty string <literal></literal> as the
-        hostname to reset the selected hostnames to their default
-        (usually <literal>localhost</literal>).</para></listitem>
+        <para>The static and transient hostnames must each be either a single DNS label (a string composed of
+        7-bit ASCII lower-case characters and no spaces or dots, limited to the format allowed for DNS domain
+        name labels), or a sequence of such labels separated by single dots that forms a valid DNS FQDN. The
+        hostname must be at most 64 characters, which is a Linux limitation (DNS allows longer names).</para>
+
+        <para>Pass the empty string <literal></literal> as the hostname to reset the selected hostnames to
+        their default (usually <literal>&FALLBACK_HOSTNAME;</literal>).</para></listitem>
       </varlistentry>
 
       <varlistentry>
diff --git a/man/os-release.xml b/man/os-release.xml
index a6d333f2780..e6162bdacfb 100644
--- a/man/os-release.xml
+++ b/man/os-release.xml
@@ -325,7 +325,8 @@
         present and no other configuration source specifies the hostname. Must be either a single DNS label
         (a string composed of 7-bit ASCII lower-case characters and no spaces or dots, limited to the format
         allowed for DNS domain name labels), or a sequence of such labels separated by single dots that forms
-        a valid DNS FQDN. The total length must be at most 64 characters.</para>
+        a valid DNS FQDN. The hostname must be at most 64 characters, which is a Linux limitation (DNS allows
+        longer names).</para>
 
         <para>See
         <citerefentry><refentrytitle>org.freedesktop.hostname1</refentrytitle><manvolnum>5</manvolnum></citerefentry>
-- 
2.47.3