root2ram.sh

# root2ram.sh
# more info: https://skyboo.net/2017/04/rpi-creating-a-ram-disk-running-linux-environment-from-nfs-booted-raspbian/

set -x
#uncomment following 2 lines to have a network in qemu:
#ip route del default
#ip route add default via 10.0.2.2 dev eth0
#setting time from NTP as the first step, otherwise all created files/dirs will have a bad dates
/usr/src/ntpclient/ntpclient -n -d -c1 -s ntp.task.gda.pl

mount -t tmpfs tmpfs /mnt
cd /mnt
mkdir dev bin proc sys run var
cp /bin/busybox ./bin
/mnt/bin/busybox --install /mnt/bin

mount --move /dev /mnt/dev

# Pivot root using instructions from pivot_root(8) man page
cd /mnt
mkdir old_root
pivot_root . old_root
# The current directory now seems invalid, so fix it
cd /

mkdir -p /etc/init.d
cp /old_root/rcS /etc/init.d/rcS

mount -t proc proc /proc
mount -t sysfs -o nosuid,nodev,noexec sysfs /sys
mount -t tmpfs -o mode=0755,nosuid,nodev tmpfs /run
mkdir -p /dev/pts
mount -t devpts -o nosuid,noexec,gid=5,mode=620 devpts /dev/pts
mkdir -p /dev/shm
mount -t tmpfs -o nosuid,nodev tmpfs /dev/shm
ln -s /run /var/run

exec chroot . /bin/init

# Old root can only be unmounted once sh running from old root finishes.
# If enough was copied, you could continue startup normally using init.