Universal deepfreeze linux

deepfreeze.sh

#!/bin/bash
if [[ -e /sbin/init-normal ]] ; then
    exit
fi
mv /sbin/init /sbin/init-normal
cat > /sbin/init <<EOF
#!/bin/bash
mount -t tmpfs tmpfs /tmp || true
mkdir -p /tmp/work/source /tmp/work/a /tmp/work/b /tmp/work/target || true
mount --bind / /tmp/work/source
mount -t overlay -o lowerdir=/tmp/work/source,upperdir=/tmp/work/a,workdir=/tmp/work/b overlay /tmp/work/target
exec chroot /tmp/work/target /sbin/init-normal
EOF
chmod 755 /sbin/init