diff --git a/man/file-hierarchy.xml b/man/file-hierarchy.xml
index 3a24eca8cea..a6e3d75695a 100644
--- a/man/file-hierarchy.xml
+++ b/man/file-hierarchy.xml
@@ -420,6 +420,25 @@
         this directory.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><filename>/sys/fs/cgroup/</filename></term>
+        <listitem><para>A virtual kernel file system exposing process
+        control groups (cgroups). This file system is an API to interface
+        with the kernel and not a place where normal files may be stored. On
+        current systems running in the default "unified" mode,
+        this directory serves as the mount point for the
+        <literal>cgroup2</literal> filesystem, which provides a unified
+        cgroup hierarchy for all resource controllers. On systems with
+        non-default configurations, this directory may instead be a tmpfs
+        filesystem containing mount points for various
+        <literal>cgroup</literal> (v1) resource controllers; in such
+        configurations, if <literal>cgroup2</literal> is mounted it will be
+        mounted on <filename>/sys/fs/cgroup/unified/</filename>, but
+        cgroup2 will not have resource controllers attached. In
+        sandboxed/containerized setups, this directory may either not exist or
+        may include a subset of functionality.
+        </para></listitem>
+      </varlistentry>
     </variablelist>
   </refsect1>