diff -up ./sysctl.conf.5.ori ./sysctl.conf.5
--- ./sysctl.conf.5.ori	2017-04-06 18:59:51.718644400 +0200
+++ ./sysctl.conf.5	2017-04-06 19:00:01.872604143 +0200
@@ -28,6 +28,15 @@ token = value
 Note that blank lines are ignored, and whitespace before and after a token or
 value is ignored, although a value can contain whitespace within.  Lines which
 begin with a # or ; are considered comments and ignored.
+.SH NOTES
+As the
+.BR /etc/sysctl.conf
+file is used to override default kernel parameter values, only a small number of parameters is predefined in the file.
+Use
+.IR /sbin/sysctl\ \-a
+or follow
+.BR sysctl (8)
+to list all possible parameters. The description of individual parameters can be found in the kernel documentation.
 .SH EXAMPLE
 .RS
 .sp