diff --git a/UPDATING b/UPDATING
--- a/UPDATING
+++ b/UPDATING
@@ -27,6 +27,13 @@
 	world, or to merely disable the most expensive debugging functionality
 	at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20241025:
+	The support for the rc_fast_and_loose variable has been removed from
+	rc.subr(8). Users setting rc_fast_and_loose on their systems are
+	advised to make sure their customizations to rc service scripts
+	do not depend on having a single shell environment shared across
+	all the rc service scripts during booting and shutdown.
+
 20241013:
 	The ciss driver was updated to cope better with hotplug events that
 	caused it to panic before, and to support more than 48 drives attached
diff --git a/libexec/rc/rc.subr b/libexec/rc/rc.subr
--- a/libexec/rc/rc.subr
+++ b/libexec/rc/rc.subr
@@ -1798,9 +1798,6 @@
 #	return value from the script.
 #	If `file' ends with `.sh' and lives in /etc/rc.d, ignore it as it's
 #	an old-style startup file.
-#	If `file' ends with `.sh' and does not live in /etc/rc.d, it's sourced
-#	into the current environment if $rc_fast_and_loose is set; otherwise
-#	it is run as a child process.
 #	If `file' appears to be a backup or scratch file, ignore it.
 #	Otherwise if it is executable run as a child process.
 #
@@ -1836,8 +1833,6 @@
 
 			if [ -n "$rc_boottrace" ]; then
 				boottrace_fn "$_file" "$_arg"
-			elif [ -n "$rc_fast_and_loose" ]; then
-				set $_arg; . $_file
 			else
 				( trap "echo Script $_file interrupted >&2 ; kill -QUIT $$" 3
 				  trap "echo Script $_file interrupted >&2 ; exit 1" 2
@@ -1909,19 +1904,8 @@
 	_file=$1
 	_arg=$2
 
-	if [ -n "$rc_fast_and_loose" ]; then
-		boottrace_sysctl "$_file start"
-		set $_arg; . $_file
-		boottrace_sysctl "$_file done"
-	else
-		_boot="${_boot}" rc_fast="${rc_fast}" autoboot="${autoboot}" \
-		    $boottrace_cmd "$_file" "$_arg"
-	fi
-}
-
-boottrace_sysctl()
-{
-	${SYSCTL} kern.boottrace.boottrace="$1"
+	_boot="${_boot}" rc_fast="${rc_fast}" autoboot="${autoboot}" \
+	    $boottrace_cmd "$_file" "$_arg"
 }
 
 #
diff --git a/share/man/man8/rc.subr.8 b/share/man/man8/rc.subr.8
--- a/share/man/man8/rc.subr.8
+++ b/share/man/man8/rc.subr.8
@@ -27,7 +27,7 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd September 22, 2024
+.Dd October 23, 2024
 .Dt RC.SUBR 8
 .Os
 .Sh NAME
@@ -1017,41 +1017,27 @@
 to enable tracing if any of those tags appear in
 .Va DEBUG_SH .
 .Pp
-The startup behaviour of
+.Ic run_rc_script
+executes
 .Ar file
-depends upon the following checks:
+unless:
 .Bl -enum
 .It
-If
 .Ar file
 ends in
-.Pa .sh ,
-it is sourced into the current shell.
+.Pa .sh
+and lives in
+.Pa /etc/rc.d .
 .It
-If
 .Ar file
 appears to be a backup or scratch file
-(e.g., with a suffix of
-.Pa ~ , # , .OLD ,
+.Po e.g., with a suffix of
+.Pa ~ , # , .OLD , ,v ,
 or
-.Pa .orig ) ,
-ignore it.
+.Pa .orig Pc .
 .It
-If
 .Ar file
-is not executable, ignore it.
-.It
-If the
-.Xr rc.conf 5
-variable
-.Va rc_fast_and_loose
-is empty,
-source
-.Ar file
-in a sub shell,
-otherwise source
-.Ar file
-into the current shell.
+is not executable.
 .El
 .It Ic run_rc_scripts Oo options Oc file ...
 Call