loader: update autoboot description and move to loader.conf.5

Document "NO" special value for the autoboot_delay and move the
description to loader.conf.5.

imp reworked some of the wording from danger's patch.

Reviewed by:		imp
PR:			85128
Differential Revision:	https://reviews.freebsd.org/D11887

(cherry picked from commit 71f6aea4150c66784cbad42c1e1ff908d909c2ec)

2 files changed, 44 insertions, 30 deletions

diff --git a/stand/defaults/loader.conf.5 b/stand/defaults/loader.conf.5
index 76ec32ef6bec..b4109371a1cf 100644
--- a/stand/defaults/loader.conf.5
+++ b/stand/defaults/loader.conf.5
@@ -23,7 +23,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\" $FreeBSD$
-.Dd January 6, 2021
+.Dd July 10, 2021
 .Dt LOADER.CONF 5
 .Os
 .Sh NAME
@@ -77,6 +77,47 @@ may have any prefix; the prefix identifies a module.
 All such settings sharing a common
 prefix refer to the same module.
 .Bl -tag -width Ar
+.It Ar autoboot_delay
+Delay in seconds before automatically booting.
+A user with console access will be able to interrupt the
+.Ic autoboot
+process and escape into the interactive mode by pressing a key on
+the console during this delay.
+.Pp
+If set to
+.Dq Li NO ,
+no
+.Ic autoboot
+is automatically attempted after processing
+.Pa /boot/loader.rc ,
+though explicit
+.Ic autoboot Ns 's
+are processed normally, using a 10 second delay.
+.Pp
+If set to
+.Dq Li 0 ,
+no delay is inserted, but any keys pressed while the kernel and modules are
+loaded will enter interactive mode.
+.Pp
+If set to
+.Dq Li -1 ,
+no delay will be inserted and
+.Nm
+starts interactive mode only if
+.Ic autoboot
+has failed.
+In combination with the
+.Va beastie_disable
+option, this option prevents users with console access from being able
+to interrupt the
+.Ic autoboot
+process and escape to the loader prompt.
+To use the
+.Va autoboot_delay
+option in this manner,
+.Va beastie_disable
+must be set to
+.Dq Li YES .
 .It Ar exec
 Immediately executes a
 .Xr loader 8
diff --git a/stand/man/loader.8 b/stand/man/loader.8
index 5e8819628822..305c736939fc 100644
--- a/stand/man/loader.8
+++ b/stand/man/loader.8
@@ -354,35 +354,8 @@ Both types of builtin variables are described below.
 Number of seconds
 .Ic autoboot
 will wait before booting.
-If this variable is not defined,
-.Ic autoboot
-will default to 10 seconds.
-.Pp
-If set to
-.Dq Li NO ,
-no
-.Ic autoboot
-will be automatically attempted after processing
-.Pa /boot/loader.rc ,
-though explicit
-.Ic autoboot Ns 's
-will be processed normally, defaulting to 10 seconds delay.
-.Pp
-If set to
-.Dq Li 0 ,
-no delay will be inserted, but user still will be able to interrupt
-.Ic autoboot
-process and escape into the interactive mode by pressing some key
-on the console while kernel and
-modules are being loaded.
-.Pp
-If set to
-.Dq Li -1 ,
-no delay will be inserted and
-.Nm
-will engage interactive mode only if
-.Ic autoboot
-has failed for some reason.
+Configuration options are described in
+.Xr loader.conf 5 .
 .It Va boot_askname
 Instructs the kernel to prompt the user for the name of the root device
 when the kernel is booted.