To use busybox's init as init I did (on a test box):

  Make available
ln -s /bin/busybox /sbin/init

  Create /etc/inittab like this:
::sysinit:/etc/rcS

tty1:12345:respawn:/sbin/agetty --noclear 38400 tty1 linux
tty2:12345:respawn:/sbin/agetty --noclear 38400 tty2 linux
tty3:2345:respawn:/sbin/agetty --noclear 38400 tty3 linux
tty4:2345:respawn:/sbin/agetty --noclear 38400 tty4 linux
tty5:2345:respawn:/sbin/agetty --noclear 38400 tty5 linux
tty6:2345:respawn:/sbin/agetty --noclear 38400 tty6 linux

::ctrlaltdel:/sbin/shutdown -r now


  Create a /etc/rcS like this:
#!/bin/sh

#sleep 3
#/sbin/sulogin -t 5

/bin/mount /proc
/bin/mount /sys
/bin/mount /config
/bin/mount /dev/pts

/bin/mount /tmp
/bin/mount /run
/bin/mkdir /run/lock
/bin/mount /run/lock
/bin/mkdir /run/shm
/bin/mount /run/shm

/sbin/fsck -p -C -V -t ext4 /dev/md2
if [ "$?" -gt 1 ]
then
  /sbin/sulogin -t 5
fi

/bin/hostname `cat /etc/hostname`

/sbin/hwclock -u -s

for i in 7 6 5 4 3 1
do
  echo mdadm -A /dev/md$i /dev/sda$i /dev/sdb$i
  /sbin/mdadm -A /dev/md$i /dev/sda$i /dev/sdb$i
done

/sbin/fsck -p -C -V -R -A
if [ "$?" -gt 1 ]
then
  /sbin/sulogin -t 5
fi

/bin/mount -a
/sbin/swapon -a

/usr/sbin/adjtimex -t 10000 -f 403859

/usr/sbin/syslogd -p /var/log/log
/usr/sbin/klogd

for file in /etc/sysctl.conf /etc/sysctl.d/*
do
  if [ -r $file ]
  then
    /sbin/sysctl --load=$file
  fi
done

/bin/ifconfig lo 127.0.0.1 netmask 255.0.0.0
/bin/route add 127.0.0.0 gw 127.0.0.1

/sbin/modprobe r8169
/bin/ifconfig eth0 angelit
/bin/route add default gw calcit

/bin/setserial -bg /dev/ttyS*

/usr/sbin/sshd
/usr/sbin/ntpd
/usr/sbin/acpid

# alsactl
# : > /var/run/utmp

  Make a suitable kernel, mine has the boot arguments and no initrd,
most things are compiled in:

md=2,/dev/sda2,/dev/sdb2 root=/dev/md2

///

the /etc/rcS is like a condensed form av debians setup on another box.
Works great!

To shutdown use "busybox poweroff" or similar.

///

Nothing hinders you to run /etc/init.d/sshd start instead of
/usr/sbin/sshd directly or useing some form of process control.
This is only an experiment on minimalism.