From 4a600af1b139c2b6df1ea22809a3fad584684207 Mon Sep 17 00:00:00 2001
From: Michael Weiss <dev.primeos@gmail.com>
Date: Sat, 10 Oct 2020 15:27:47 +0200
Subject: [PATCH] doc: Document a workaround for using an FQDN as hostname

Since #76542 this workaround is required to use a FQDN as hostname. See
#94011 and #94022 for the related discussion. Due to some
potential/unresolved issues (legacy software, backward compatibility,
etc.) we're documenting this workaround [0].

[0]: https://github.com/NixOS/nixpkgs/issues/94011#issuecomment-705952300
---
 nixos/doc/manual/release-notes/rl-2009.xml | 8 ++++++--
 nixos/modules/tasks/network-interfaces.nix | 4 ++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/nixos/doc/manual/release-notes/rl-2009.xml b/nixos/doc/manual/release-notes/rl-2009.xml
index 21686841c28..91a01f0835a 100644
--- a/nixos/doc/manual/release-notes/rl-2009.xml
+++ b/nixos/doc/manual/release-notes/rl-2009.xml
@@ -605,8 +605,8 @@ systemd.services.nginx.serviceConfig.ReadWritePaths = [ "/var/www" ];
    <listitem>
      <para>
        In addition to the hostname, the fully qualified domain name (FQDN),
-       which consists of <literal>${cfg.hostName}</literal> and
-       <literal>${cfg.domain}</literal> is now added to
+       which consists of <literal>${networking.hostName}</literal> and
+       <literal>${networking.domain}</literal> is now added to
        <literal>/etc/hosts</literal>, to allow local FQDN resolution, as used by the
        <literal>hostname --fqdn</literal> command and other applications that
        try to determine the FQDN. These new entries take precedence over entries
@@ -626,6 +626,10 @@ systemd.services.nginx.serviceConfig.ReadWritePaths = [ "/var/www" ];
        or digit, and have as interior characters only letters, digits, and
        hyphen. The maximum length is 63 characters. Additionally it is
        recommended to only use lower-case characters.
+       If (e.g. for legacy reasons) a FQDN is required as the Linux kernel network node hostname
+       (<literal>uname --nodename</literal>) the option
+       <literal>boot.kernel.sysctl."kernel.hostname"</literal>
+       can be used as a workaround (but be aware of the 64 character limit).
      </para>
    </listitem>
    <listitem>
diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
index 5ddb12d15c3..e5bd5775368 100644
--- a/nixos/modules/tasks/network-interfaces.nix
+++ b/nixos/modules/tasks/network-interfaces.nix
@@ -391,6 +391,10 @@ in
         end with a letter or digit, and have as interior characters only
         letters, digits, and hyphen. The maximum length is 63 characters.
         Additionally it is recommended to only use lower-case characters.
+        If (e.g. for legacy reasons) a FQDN is required as the Linux kernel
+        network node hostname (uname --nodename) the option
+        boot.kernel.sysctl."kernel.hostname" can be used as a workaround (but
+        the 64 character limit still applies).
       '';
     };