Merge pull request #197986 from flokli/rl-nsncd

nixos/doc/rl-2211: document nsncd option

nixos/doc/manual/from_md/release-notes/rl-2211.section.xml

@@ -77,6 +77,32 @@
           with any supported NixOS release.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          <literal>nscd</literal> functionality, necessary to provide
+          non-glibc-builtin NSS modules (such as
+          <literal>nss_systemd</literal> or <literal>nss_ldap</literal>)
+          can now be provided by <literal>nsncd</literal>, by setting
+          <literal>services.nscd.enableNsncd</literal> to
+          <literal>true</literal>.
+        </para>
+        <para>
+          The <literal>nscd</literal> daemon provided by glibc, which is
+          currently used by NixOS isn’t very reliable. For example, it’s
+          <link xlink:href="https://github.com/NixOS/nixpkgs/issues/135888">not
+          fully possible to disable caching functionality</link>,
+          causing various issues and failed lookups.
+        </para>
+        <para>
+          In contrast to nscd’s behavior of caching module responses on
+          its own, nsncd merely forwards requests to NSS modules, which
+          might cache or not.
+        </para>
+        <para>
+          We plan to use <literal>nsncd</literal> by default in NixOS
+          23.05.
+        </para>
+      </listitem>
       <listitem>
         <para>
           <literal>emacs</literal> enables native compilation which

nixos/doc/manual/release-notes/rl-2211.section.md

@@ -38,6 +38,20 @@ In addition to numerous new and upgraded packages, this release has the followin
   for a transition period so that in time the ecosystem can switch without
   breaking compatibility with any supported NixOS release.
 
+- `nscd` functionality, necessary to provide non-glibc-builtin NSS
+  modules (such as `nss_systemd` or `nss_ldap`) can now be provided by
+  `nsncd`, by setting `services.nscd.enableNsncd` to `true`.
+
+  The `nscd` daemon provided by glibc, which is currently used by NixOS isn't
+  very reliable. For example, it's [not fully possible to disable caching
+  functionality](https://github.com/NixOS/nixpkgs/issues/135888), causing
+  various issues and failed lookups.
+
+  In contrast to nscd's behavior of caching module responses on its own,
+  nsncd merely forwards requests to NSS modules, which might cache or not.
+
+  We plan to use `nsncd` by default in NixOS 23.05.
+
 - `emacs` enables native compilation which means:
   - emacs packages from nixpkgs, builtin or not, will do native compilation ahead of time so you can enjoy the benefit of native compilation without compiling them on you machine;
   - emacs packages from somewhere else, e.g. `package-install`, will do asynchronously deferred native compilation. If you do not want this, maybe to avoid CPU consumption for compilation, you can use `(setq native-comp-deferred-compilation nil)` to disable it while still enjoy the benefit of native compilation for packages from nixpkgs.