replace systemd with a simple busybox inittab

1. install busybox
2. create file /etc/inittab with the following content:
# Start "rc init" on boot
::sysinit:/opt/rc init

# Set up the TTY's 1 through 4
tty1::askfirst:/sbin/agetty -8 -s 38400 tty1 linux
tty2::respawn:/sbin/agetty -8 -s 38400 tty2 linux

# Stop all services on shutdown
::shutdown:/opt/rc shutdown

# Killing everything on shutdown
::shutdown:echo :: sending SIGTERM to all
::shutdown:/bin/kill -s TERM -1
::shutdown:sleep 1
::shutdown:echo :: sending SIGKILL to all
::shutdown:/bin/kill -s KILL -1

# Unmount everything on shutdown
::shutdown:echo :: unmounting everything
::shutdown:/bin/umount -a -r
::shutdown:/bin/mount -o remount,ro /

3. ln -s /bin/busybox /opt/init

4. create /opt/rc with the following content:

#!/bin/sh

on_boot() {

    #===================

    # mount the API filesystem

    # /proc, /sys, /run, /dev, /run/lock, /dev/pts, /dev/shm

    echo 3 mounting API filesystem...

    mountpoint -q /proc    || mount -t proc proc /proc -o nosuid,noexec,nodev

    mountpoint -q /sys     || mount -t sysfs sys /sys -o nosuid,noexec,nodev

    mountpoint -q /run     || mount -t tmpfs run /run -o mode=0755,nosuid,nodev

    mountpoint -q /dev     || mount -t devtmpfs dev /dev -o mode=0755,nosuid

    mkdir -p /dev/pts /dev/shm

    mountpoint -q /dev/pts || mount -t devpts devpts /dev/pts -o mode=0620,gid=5,nosuid,noexec

    mountpoint -q /dev/shm || mount -t tmpfs shm /dev/shm -o mode=1777,nosuid,nodev

    #===================

    # initialize system

    echo 3 setting up loopback device...

    /usr/sbin/ip link set up dev lo

    echo 3 initializing udev...

        busybox mdev -s

        echo /sbin/mdev > /proc/sys/kernel/hotplug

    echo 3 setting hostname...

    cat /etc/hostname >| /proc/sys/kernel/hostname

    echo 3 mounting...

    mount -a

    mount -o remount,rw /

        dhclient eth0&

        /etc/init.d/ssh start&

}

on_shutdown() {

    #===================

    echo 3 shutting down udev...

        killall busybox

        killall mdev

    #===================

    # umount the API filesystem

    echo 3 unmounting API filesystem...

    umount -r /run

}

#===================

# handle arguments

case "$1" in

init)

    on_boot;;

shutdown)

    on_shutdown;;

esac

5. reboot and add the following parameter to your kernel command line on grub:

init=/opt/init

Enjoy