diff --git a/share/man/man8/beinstall.8 b/share/man/man8/beinstall.8
index e403f25d2f35..114483ba752a 100644
--- a/share/man/man8/beinstall.8
+++ b/share/man/man8/beinstall.8
@@ -1,137 +1,128 @@
 .\"
 .\" SPDX-License-Identifier: BSD-2-Clause
 .\"
 .\" Copyright (c) 2018 Mateusz Piotrowski <0mp@FreeBSD.org>
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .Dd October 30, 2020
 .Dt BEINSTALL.SH 8
 .Os
 .Sh NAME
 .Nm beinstall.sh
 .Nd "install a boot environment using the current FreeBSD source tree"
 .Sh SYNOPSIS
 .Nm
 .Op Ar options Ar ...
 .Sh DESCRIPTION
 .Nm
 installs a boot environment using the current
 .Fx
 source tree.
 .Nm
 also automatically performs
 .Pa /etc
 updates
-(using either
-.Xr etcupdate 8
-or
-.Xr mergemaster 8 )
+(using
+.Xr etcupdate 8 )
 and
 package updates using
 .Xr pkg-upgrade 8
 automatically in the new boot environment sandbox.
 .Pp
 Upon successful completion, the system will be ready to boot into the new boot
 environment.
 Upon failure, the target boot environment will be destroyed.
 In all cases, the running system is left untouched
 and a reboot into a partially updated system
 (due to install or hardware failure) cannot happen.
 Additionally, the full installation process requires
 only one reboot as it is performed
 in a new boot environment.
 .Pp
 .Nm
 requires a fully built world and kernel.
 It also requires
 .Xr pkg 8 ,
 which is not present in the base system and has to be installed manually.
 .Pp
 The
 .Ar options
 provided to
 .Nm
 are world and kernel flags like
 .Ev KERNCONF
 as described in
 .Xr build 7 .
 .Sh ENVIRONMENT
 User modifiable variables.
 Set these in the environment if desired:
 .Bl -tag -width indent
 .It Ev BE_UTILITY Pq default: Dq Li "bectl"
 Utility to manage ZFS boot environments.
 This can be either
 .Xr bectl 8
 from the base system or
 .Xr beadm 1
 from ports (sysutils/beadm).
 .It Ev CONFIG_UPDATER Pq default: Dq Li "etcupdate"
 Config updater:
 .Xr etcupdate 8
-and
-.Xr mergemaster 8
-are supported.
+is supported.
 Set to an empty string to skip.
 .It Ev ETCUPDATE_FLAGS Pq default: Dq Li "-F"
 Flags for
 .Xr etcupdate 8
 if used.
-.It Ev MERGEMASTER_FLAGS Pq default: Dq Li "-iFU"
-Flags for
-.Xr mergemaster 8
-if used.
 .It Ev NO_PKG_UPGRADE Pq default: Dq Li ""
 If not empty,
 .Dq Li pkg upgrade
 will be skipped.
 .El
 .Sh FILES
 .Bl -tag -width indent
 .It Sy src/ Ns Pa tools/build/beinstall.sh
 Place where
 .Nm
 lives in the src tree.
 .El
 .Sh SEE ALSO
 .Xr build 7 ,
 .Xr development 7 ,
 .Xr bectl 8 ,
 .Xr etcupdate 8 ,
-.Xr mergemaster 8 ,
 .Xr pkg 8
 .Sh HISTORY
 .Nm
 is inspired by and similar in function to
 Solaris/illumos-style upgrades.
 .Pp
 The
 .Nm
 manual page first appeared in
 .Fx 12.0 .
 .Sh AUTHORS
 The
 .Nm
 script was implemented by
 .An Will Andrews Aq Mt will@FreeBSD.org .
 This manual page was written by
 .An Mateusz Piotrowski Aq Mt 0mp@FreeBSD.org .
diff --git a/tools/build/beinstall.sh b/tools/build/beinstall.sh
index 766a3a03739f..7f7481b671f5 100755
--- a/tools/build/beinstall.sh
+++ b/tools/build/beinstall.sh
@@ -1,263 +1,250 @@
 #!/bin/sh
 #
 # Copyright (c) 2016 Will Andrews
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 # 1. Redistributions of source code must retain the above copyright
 #    notice, this list of conditions and the following disclaimer 
 #    in this position and unchanged.
 # 2. Redistributions in binary form must reproduce the above copyright
 #    notice, this list of conditions and the following disclaimer in the
 #    documentation and/or other materials provided with the distribution.
 #
 # THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 # IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 # OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 # IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 # NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 #
 ##
 # Install a boot environment using the current FreeBSD source tree.
 # Requires a fully built world & kernel.
 #
 # Non-base tools required: pkg
 #
 # In a sandbox for the new boot environment, this script also runs etcupdate
 # and pkg upgrade automatically in the sandbox.  Upon successful completion,
 # the system will be ready to boot into the new boot environment.  Upon
 # failure, the target boot environment will be destroyed.  In all cases, the
 # running system is left untouched.
 #
 ## Usage:
 # beinstall [optional world/kernel flags e.g. KERNCONF]
 #
 ## User modifiable variables - set these in the environment if desired.
 # Utility to manage ZFS boot environments.
 BE_UTILITY="${BE_UTILITY:-"bectl"}"
 # If not empty, 'pkg upgrade' will be skipped.
 NO_PKG_UPGRADE="${NO_PKG_UPGRADE:-""}"
-# Config updater - 'etcupdate' and 'mergemaster' are supported.  Set to an
-# empty string to skip.
+# Config updater - 'etcupdate' is supported.  Set to an empty string to skip.
 CONFIG_UPDATER="${CONFIG_UPDATER:-"etcupdate"}"
 # Flags for etcupdate if used.
 ETCUPDATE_FLAGS="${ETCUPDATE_FLAGS:-"-F"}"
-# Flags for mergemaster if used.
-MERGEMASTER_FLAGS="${MERGEMASTER_FLAGS:-"-iFU"}"
 
 
 ########################################################################
 ## Functions
 cleanup() {
 	[ -z "${cleanup_commands}" ] && return
 	echo "Cleaning up ..."
 	for command in ${cleanup_commands}; do
 		${command}
 	done
 }
 
 errx() {
 	cleanup
 	echo "error: $@"
 	exit 1
 }
 
 rmdir_be() {
 	chflags -R noschg ${BE_MNTPT}
 	rm -rf ${BE_MNTPT}
 }
 
 unmount_be() {
 	mount | grep " on ${BE_MNTPT}" | awk '{print $3}' | sort -r | xargs -t umount -f
 }
 
 copy_pkgs() {
 	# Before cleaning up, try to save progress in pkg(8) updates, to
 	# speed up future updates.  This is only called on the error path;
 	# no need to run on success.
 	echo "Rsyncing back newly saved packages..."
 	rsync -av --progress ${BE_MNTPT}/var/cache/pkg/. /var/cache/pkg/.
 }
 
 cleanup_be() {
 	# Before destroying, unmount any child filesystems that may have
 	# been mounted under the boot environment.  Sort them in reverse
 	# order so children are unmounted first.
 	unmount_be
 	# Finally, clean up any directories that were created by the
 	# operation, via cleanup_be_dirs().
 	if [ -n "${created_be_dirs}" ]; then
 		chroot ${BE_MNTPT} /bin/rm -rf ${created_be_dirs}
 	fi
 	${BE_UTILITY} destroy -F ${BENAME}
 }
 
 create_be_dirs() {
 	echo "${BE_MNTPT}: Inspecting dirs $*"
 	for dir in $*; do
 		curdir="$dir"
 		topdir="$dir"
 		while :; do
 			[ -e "${BE_MNTPT}${curdir}" ] && break
 			topdir=$curdir
 			curdir=$(dirname ${curdir})
 		done
 		[ "$curdir" = "$dir" ] && continue
 
 		# Add the top-most nonexistent directory to the list, then
 		# mkdir -p the innermost directory specified by the argument.
 		# This way the least number of directories are rm'd directly.
 		created_be_dirs="${topdir} ${created_be_dirs}"
 		echo "${BE_MNTPT}: Created ${dir}"
 		mkdir -p ${BE_MNTPT}${dir} || return $?
 	done
 	return 0
 }
 
-update_mergemaster_pre() {
-	${MERGEMASTER_CMD} -p -m ${srcdir} -D ${BE_MNTPT} -t ${BE_MM_ROOT} ${MERGEMASTER_FLAGS}
-}
-
-update_mergemaster() {
-	${MERGEMASTER_CMD} -m ${srcdir} -D ${BE_MNTPT} -t ${BE_MM_ROOT} ${MERGEMASTER_FLAGS}
-}
-
 update_etcupdate_pre() {
 	${ETCUPDATE_CMD} -p -s ${srcdir} -D ${BE_MNTPT} ${ETCUPDATE_FLAGS} || return $?
 	${ETCUPDATE_CMD} resolve -D ${BE_MNTPT} || return $?
 }
 
 update_etcupdate() {
 	chroot ${BE_MNTPT} \
 		${ETCUPDATE_CMD} -s ${srcdir} ${ETCUPDATE_FLAGS} || return $?
 	chroot ${BE_MNTPT} ${ETCUPDATE_CMD} resolve
 }
 
 
 # Special command-line subcommand that can be used to do a full cleanup
 # after a manual post-mortem has been completed.
 postmortem() {
 	[ -n "${BENAME}" ] || errx "Must specify BENAME"
 	[ -n "${BE_MNTPT}" ] || errx "Must specify BE_MNTPT"
 	echo "Performing post-mortem on BE ${BENAME} at ${BE_MNTPT} ..."
 	unmount_be
 	rmdir_be
 	echo "Post-mortem cleanup complete."
 	echo "To destroy the BE (recommended), run: ${BE_UTILITY} destroy ${BENAME}"
 	echo "To instead continue with the BE, run: ${BE_UTILITY} activate ${BENAME}"
 }
 
 if [ -n "$BEINSTALL_CMD" ]; then
 	${BEINSTALL_CMD} $*
 	exit $?
 fi
 
 if [ "$(basename -- "${BE_UTILITY}")" = "bectl" ]; then
 	${BE_UTILITY} check || errx "${BE_UTILITY} sanity check failed"
 fi
 
 cleanup_commands=""
 trap 'errx "Interrupt caught"' HUP INT TERM
 
 [ "$(whoami)" != "root" ] && errx "Must be run as root"
 
 [ ! -f "Makefile.inc1" ] && errx "Must be in FreeBSD source tree"
 srcdir=$(pwd)
 objdir=$(make -V .OBJDIR 2>/dev/null)
 [ ! -d "${objdir}" ] && errx "Must have built FreeBSD from source tree"
 
 ## Constants
 ETCUPDATE_CMD="${srcdir}/usr.sbin/etcupdate/etcupdate.sh"
-MERGEMASTER_CMD="${srcdir}/usr.sbin/mergemaster/mergemaster.sh"
 
 # May be a worktree, in which case .git is a file, not a directory.
 if [ -e .git ] ; then
     commit_time=$(git show -s --format='%ct' 2>/dev/null)
     [ $? -ne 0 ] && errx "Can't lookup git commit timestamp"
     commit_ts=$(date -r ${commit_time} '+%Y%m%d.%H%M%S')
 elif [ -d .svn ] ; then
       if [ -e /usr/bin/svnlite ]; then
         svn=/usr/bin/svnlite
       elif [ -e /usr/local/bin/svn ]; then
         svn=/usr/local/bin/svn
       else
         errx "Unable to find subversion"
       fi
       commit_ts="$( "$svn" info --show-item last-changed-date | sed -e 's/\..*//' -e 's/T/./' -e 's/-//g' -e s'/://g' )"
     [ $? -ne 0 ] && errx "Can't lookup Subversion commit timestamp"
 else
     errx "Unable to determine source control type"
 fi
 
 commit_ver=$(${objdir}/bin/freebsd-version/freebsd-version -u 2>/dev/null)
 [ -z "${commit_ver}" ] && errx "Unable to determine FreeBSD version"
 
 BENAME="${commit_ver}-${commit_ts}"
 
 BE_TMP=$(mktemp -d /tmp/beinstall.XXXXXX)
 [ $? -ne 0 -o ! -d ${BE_TMP} ] && errx "Unable to create mountpoint"
 [ -z "$NO_CLEANUP_BE" ] && cleanup_commands="rmdir_be ${cleanup_commands}"
 BE_MNTPT=${BE_TMP}/mnt
-BE_MM_ROOT=${BE_TMP}/mergemaster # mergemaster will create
 mkdir -p ${BE_MNTPT}
 
 ${BE_UTILITY} create ${BENAME} >/dev/null || errx "Unable to create BE ${BENAME}"
 [ -z "$NO_CLEANUP_BE" ] && cleanup_commands="cleanup_be ${cleanup_commands}"
 
 ${BE_UTILITY} mount ${BENAME} ${BE_TMP}/mnt || errx "Unable to mount BE ${BENAME}."
 
 echo "Mounted ${BENAME} to ${BE_MNTPT}, performing install/update ..."
 make "$@" DESTDIR=${BE_MNTPT} installkernel || errx "Installkernel failed!"
 if [ -n "${CONFIG_UPDATER}" ]; then
 	"update_${CONFIG_UPDATER}_pre"
 	[ $? -ne 0 ] && errx "${CONFIG_UPDATER} (pre-world) failed!"
 fi
 
 # Mount the source and object tree within the BE in order to account for any
 # changes applied by the pre-installworld updater.  Cleanup any directories
 # created if they didn't exist previously.
 create_be_dirs "${srcdir}" "${objdir}" || errx "Unable to create BE dirs"
 mount -t nullfs "${srcdir}" "${BE_MNTPT}${srcdir}" || errx "Unable to mount src"
 mount -t nullfs "${objdir}" "${BE_MNTPT}${objdir}" || errx "Unable to mount obj"
 mount -t devfs devfs "${BE_MNTPT}/dev" || errx "Unable to mount devfs"
 
 chroot ${BE_MNTPT} make "$@" -C ${srcdir} installworld || \
 	errx "Installworld failed!"
 
 if [ -n "${CONFIG_UPDATER}" ]; then
 	"update_${CONFIG_UPDATER}"
 	[ $? -ne 0 ] && errx "${CONFIG_UPDATER} (post-world) failed!"
 fi
 
 if which rsync >/dev/null 2>&1; then
 	cleanup_commands="copy_pkgs ${cleanup_commands}"
 fi
 
 BE_PKG="chroot ${BE_MNTPT} env ASSUME_ALWAYS_YES=true pkg"
 if [ -z "${NO_PKG_UPGRADE}" ]; then
 	${BE_PKG} update || errx "Unable to update pkg"
 	${BE_PKG} upgrade || errx "Unable to upgrade pkgs"
 fi
 
 if [ -n "$NO_CLEANUP_BE" ]; then
 	echo "Boot Environment ${BENAME} may be examined in ${BE_MNTPT}."
 	echo "Afterwards, run this to cleanup:"
 	echo "  env BENAME=${BENAME} BE_MNTPT=${BE_MNTPT} BEINSTALL_CMD=postmortem $0"
 	exit 0
 fi
 
 unmount_be || errx "Unable to unmount BE"
 rmdir_be || errx "Unable to cleanup BE"
 ${BE_UTILITY} activate ${BENAME} || errx "Unable to activate BE"
 echo
 ${BE_UTILITY} list
 echo
 echo "Boot environment ${BENAME} setup complete; reboot to use it."