rc(8): document how to reload rc's configuration

The fact that rc(8) only reads its configuration once is in the man
page, but how to trigger a reload is only in the code.

Discovered while trying to make cloud-init disable and stop syslogd.

Thanks to RhodiumToad for providing the words.

Reviewed by:           debdrup, grahamperrin
Approved by:           grahamperrin, imp
Sponsored by:          The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D40329

(cherry picked from commit 0981275c75d5678172eb9dd8fbc89ef61c05c979)

1 files changed, 14 insertions, 4 deletions

diff --git a/share/man/man8/rc.8 b/share/man/man8/rc.8
index 8b6fc094b7db..14cc83d8e32d 100644
--- a/share/man/man8/rc.8
+++ b/share/man/man8/rc.8
@@ -31,7 +31,7 @@
 .\"     @(#)rc.8	8.2 (Berkeley) 12/11/93
 .\" $FreeBSD$
 .\"
-.Dd July 4, 2022
+.Dd June 1, 2023
 .Dt RC 8
 .Os
 .Sh NAME
@@ -124,10 +124,9 @@ to load various
 .Xr rc.subr 8
 shell functions to use.
 .It
-Load the configuration files.
+Load the configuration files (see below for reloading).
 .It
-Determine if booting in a jail,
-and add
+Determine if booting in a jail, and add
 .Dq Li nojail
 (no jails allowed) or
 .Dq Li nojailvnet
@@ -371,6 +370,17 @@ the command name (see the
 .Sx EXAMPLES
 section).
 .Pp
+The configuration files are normally read only once at the start of a boot
+sequence; if a script needs to
+.Cm enable
+or
+.Cm disable
+any other script that would run later in the sequence, it must send a
+.Dv SIGALRM
+to the rc process (identified by
+.Ev $RC_PID )
+to have it re-read the files.
+.Pp
 The following key points apply to old-style scripts in
 .Pa /usr/local/etc/rc.d/ :
 .Bl -bullet