diff --git a/man/file-hierarchy.xml b/man/file-hierarchy.xml
index 2c80c2c1a9..996876f48a 100644
--- a/man/file-hierarchy.xml
+++ b/man/file-hierarchy.xml
@@ -589,6 +589,19 @@
directives of service units (see
systemd.unit5
for details).
+
+ /tmp/, /var/tmp/ and /dev/shm/
+ should be mounted and , which means that set-user-id mode
+ and character or block special devices are not interpreted on those file systems. In general it is not
+ possible to mount them , because various programs use those directories for
+ dynamically generated or optimized code, and with that flag those use cases would break. Using this flag
+ is OK on special-purpose installations or systems where all software that may be installed is known and
+ doesn't require such functionality. See the discussion of
+ // in mount8 and
+ PROT_EXEC in mmap2.
+