busybox-init

#!/bin/sh
set -euox pipefail

# http://www.linuxfromscratch.org/lfs/view/6.1/chapter06/kernfs.html
mkdir -p /dev /proc /sys /run /var

# /dev
mount -nvt tmpfs tmpfs /dev
mkdir -vp /dev/pts
mkdir -vp /dev/shm
mount -nvt tmpfs tmpfs /dev/shm
mknod -m 444 /dev/random c 1 8
mknod -m 444 /dev/urandom c 1 9
mknod -m 666 /dev/ptmx c 5 2
mknod -m 666 /dev/tty c 5 0
# As in ../image2initrd-fakeroot:
mknod -m 666 /dev/null c 1 3
mknod -m 666 /dev/zero c 1 5
mknod -m 600 /dev/console c 5 1

mount -nvt devpts -o gid=4,mode=620 devpts /dev/pts

# /proc, /sys, /run
mount -nvt proc proc /proc
mount -nvt sysfs sysfs /sys
mount -nvt tmpfs tmpfs /run
ln -s /run /var/run

# https://tldp.org/LDP/lfs/LFS-BOOK-6.1.1-HTML/chapter06/devices.html
ln -sv /proc/self/fd /dev/fd
ln -sv /proc/self/fd/0 /dev/stdin
ln -sv /proc/self/fd/1 /dev/stdout
ln -sv /proc/self/fd/2 /dev/stderr
ln -sv /proc/kcore /dev/core

# http://www.linuxfromscratch.org/lfs/view/10.0-rc1/chapter07/createfiles.html
ln -sv /proc/self/mounts /etc/mtab

# Networking
ifconfig lo 127.0.0.1
echo auto eth0 >>/etc/network/interfaces
echo iface eth0 inet dhcp >>/etc/network/interfaces
if [ -d /sys/class/net/eth0 ] ; then
    ifup -v eth0
fi

# Enter interactive root shell on console
export HOME=/root
export TERM=linux
/bin/sh