Add new rc: machine_id to generate /etc/machine-id

This new default-enabled rc will generate a /etc/machine-id file if it
does not exist, and pre-fill it with a newly generated UUID of version 4
[2].

The file is generated in /var/db/machine-id and symlinked to
/etc/machine-id to allow for read-only root partitions.

This file is amongst other things used by libraries like GLib.

Bump FreeBSD version 1400076 to be able to easily add support for older
version of FreeBSD via a package.

[1] Linux machine-id(5): https://www.man7.org/linux/man-pages/man5/machine-id.5.html
[2] f176fe8e7f

Approved by:		bapt
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D37722

etc/Makefile

@@ -59,6 +59,8 @@ distribution:
 	${_+_}cd ${SRCTOP}/usr.sbin/rmt; ${MAKE} etc-rmt
 	${INSTALL_SYMLINK} -T "package=runtime" ../var/run/os-release \
 		${DESTDIR}/etc/os-release
+	${INSTALL_SYMLINK} -T "package=runtime" ../var/db/machine-id \
+		${DESTDIR}/etc/machine-id
 .if ${MK_UNBOUND} != "no"
 	if [ ! -e ${DESTDIR}/etc/unbound ]; then \
 		${INSTALL_SYMLINK} -T "package=unbound" \

libexec/rc/rc.conf

@@ -694,6 +694,9 @@ harvest_mask="511"	# Entropy device harvests all but the very invasive sources.
 osrelease_enable="YES"	# Update /var/run/os-release on boot (or NO).
 osrelease_file="/var/run/os-release" # File to update for os-release.
 osrelease_perms="444"	# Default permission for os-release file.
+machine_id_enable="YES"	# Create /var/db/machine-id on boot if missing (or NO).
+machine_id_file="/var/db/machine-id"	# File to update for machine-id.
+machine_id_perms="444"	# Default permissions for machine-id file.
 dmesg_enable="YES"	# Save dmesg(8) to /var/run/dmesg.boot
 watchdogd_enable="NO"	# Start the software watchdog daemon
 watchdogd_flags=""	# Flags to watchdogd (if enabled)

libexec/rc/rc.d/Makefile

@@ -52,6 +52,7 @@ CONFS=	DAEMON \
 	local \
 	localpkg \
 	lockd \
+	machine_id \
 	mixer \
 	motd \
 	mountcritlocal \

libexec/rc/rc.d/machine_id

@@ -0,0 +1,34 @@
+#!/bin/sh
+#
+# $FreeBSD$
+#
+
+# PROVIDE: machine_id
+# REQUIRE: mountcritremote FILESYSTEMS
+# BEFORE:  LOGIN
+
+. /etc/rc.subr
+
+: ${machine_id_file:=/var/db/machine-id}
+: ${machine_id_perms:=444}
+name="machine_id"
+desc="Update ${machine_id_file}"
+rcvar="machine_id_enable"
+start_cmd="machine_id_start"
+stop_cmd=":"
+
+
+machine_id_start()
+{
+	if [ ! -f ${machine_id_file} ] ; then
+		startmsg -n "Creating ${machine_id_file} "
+		t=$(mktemp -t machine-id)
+		/bin/uuidgen -r -o $t
+		install -C -o root -g wheel -m ${machine_id_perms} "$t" "${machine_id_file}"
+		rm -f "$t"
+		startmsg 'done.'
+	fi
+}
+
+load_rc_config $name
+run_rc_command "$1"

sys/sys/param.h

@@ -76,7 +76,7 @@
  * cannot include sys/param.h and should only be updated here.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1400075
+#define __FreeBSD_version 1400076
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,