I do not which ones of my runit scripts could be of use, since let's be honest, most of them are a dead simple. The process is dead simple: read the daemon's manual, search for the word: "PID", "fork", "background", "syslog"... this kind of stuff. Note the option that allows to disable those "features". Usually, it means running in what the author call "debug mode", and write your one-liner...

There are few exceptions, though, the most notable one being the cursed udevd. This is technically NOT my script, at least the ugly trick is something I've found like 10 years ago on some random blog post. I do not want to claim I did it, but this really helped me back then and I am unable to find anew the original author. I have integrated it along my system, as well, so I modified it a tiny bit.

DISCLAIMER: my computers are a mess, and I have several variants of some of those scripts, for random and idiotic reasons. Some are cleaner than others... I've been carrying those things since a decade, after all.

Here is the /etc/sv/udev cursed script, adapted to devuan (because debian ofc can't refrain shuffling files randomly every major version they do, and devuan fixed that toward the sane way... /complains):

#!/bin/sh

. /etc/runit/common

need()
{
	i=0
	while ! test -e "$1"
	do
		sleep "0.$i"
		test "$i" = 9 || i=$((i+1))
	done
}

mkdir -p /run/udev
rm -f /run/udev/control #just in case
rm -f /run/udevd_ready #just in case
(
	need /run/udev/control # not sure we really need to wait for it
	echo "Trigger+settle:"
	udevadm --debug trigger --type=subsystems --action=add
	udevadm --debug trigger --type=devices --action=add
	udevadm --debug settle
	>/run/udevd_ready
	echo "Done: trigger+settle"
) &

echo "Starting $SVNAME"
exec env - PATH="$PATH" /usr/sbin/udevd -N late

It starts, like all my runit scripts, by sourcing a single, trivial script I name /etc/runit/common:

#!/bin/sh

#this file provides some automatic features for runit daemons
#notably it:
#* provides the variable SVNAME, which is the name of the daemon dir
#* provides the die() function
#* sources an existing ./conf file
#* automatically rotates logs on startup if there are logs and AUTO_ROTATE=yes
#* redirects stderr to stdout
#* enables some shell verbosity and safeties (-xe)

die()
{
  printf "%s\n" "$@" | tee ./down
  exit 1
}

SVNAME="$(basename $(pwd))"
HAS_LOG="$(test -d "$(pwd)/log" && printf "yes")"
exec 0<&-
exec 2>&1
set -xe
test -f conf && . ./conf

if test "$0" = "run"
then
  if test "$SVNAME" = "log"
  then
    SVLOG="$(basename $(dirname $(pwd)))"
    SVNAME="${SVLOG}/${SVNAME}"
    AUTO_ROTATE="${AUTO_ROTATE:="no"}"
  fi  
  test "yes" = "${AUTO_ROTATE}" -a "yes" = "$HAS_LOG" && \
    sv alarm "$(pwd)/log"
fi

I also have a generic logger, so when I create a new service, I only create the log dir, and symlink it as "run", so it's named /etc/runit/log.run:

#!/bin/sh

SVLOG="$(basename $(dirname $(pwd)))"
LOG_PATH="/var/log/$SVLOG"
test -e "$LOG_PATH" || install -d -m 0750 -o root -g adm "$LOG_PATH"
exec svlogd -tt "$LOG_PATH"

I also have /etc/runit/global.finish which does not do much:

#!/bin/sh

. /etc/runit/common

echo "Stopped $SVNAME"

Maybe my networking stuff may be of interest, as I do not use ifupdown, networkd or whatever...

#!/bin/sh

. /etc/runit/common

ip l set $IFACE up
if test -e /sbin/ethtool
then
	while $(/sbin/ethtool $IFACE | grep -q 'Link detected: no')
	do
		test "$VERBOSE" = "yes" && echo "$IFACE unplugged, sleep ${SLEEP:=60}"
		sleep ${SLEEP:=60}
	done
fi

echo "Starting $SVNAME on $IFACE"
exec udhcpc -i $IFACE -f -R -n

This stuff is not worth much, but apparently nothing does that kind of things in devuan? Or I could not find it, which seems more likely. I've been using those (or slight modifications, I do that for my own user, too, and similarly adjust the stuff on my toy server, and used to have a 250+ fleet of street equipments at work) since more than 10 years, as said, and this requires zero maintenance. I'm a lazy person, and thus runit have kept me happy for long. I'm expecting this happiness to last, because it's a sane program, which can handle whatever I want with just few lines of shell.

The logic behind the finish and even the starting is that it makes it dead simple, when reading your logs, to know when the daemon actually started and ended. Which I have found to be extremely useful, but YMMV. I would never remove those from system, clearly, but it's not really orthodox, I suppose.

That's it. I have a lot more runit stuff, on my systems, the only stuff which are not migrated are the services which do not spawn a daemon, mostly out of lazyness.