Script to create a minimal chroot with busybox, dropbear and dtach and allow ssh access on port 5022

create_start_minichroot.sh

#!/bin/bash


CHROOTDIR=/opt/minichroot

mkdir -p ${CHROOTDIR}/bin
mkdir -p ${CHROOTDIR}/lib64
mkdir -p ${CHROOTDIR}/etc/dropbear
mkdir -p ${CHROOTDIR}/dev
mkdir -p ${CHROOTDIR}/tmp
mkdir -p ${CHROOTDIR}/lib/x86_64-linux-gnu

cp $(which dropbear) ${CHROOTDIR}/bin
cp $(which busybox) ${CHROOTDIR}/bin

#ldd ${CHROOTDIR}/bin/dropbear | awk '/lib/{print $3}' |
#	while read f
#	do
#		[ -z $f ] && continue
#		echo "copy lib: $f"
#		mkdir -p ${CHROOTDIR}/$(dirname $f)
#		cp $f ${CHROOTDIR}/$f;
#	done

cp /lib64/ld-linux-x86-64.so.2 ${CHROOTDIR}/lib64
cp /usr/bin/dtach ${CHROOTDIR}/bin/

mount -o bind,ro /lib/x86_64-linux-gnu ${CHROOTDIR}/lib/x86_64-linux-gnu
mount -t devtmpfs udev ${CHROOTDIR}/dev
mkdir ${CHROOTDIR}/dev/pts
mount -t devpts devpts ${CHROOTDIR}/dev/pts

echo "creating user: user with password: user"
cat > ${CHROOTDIR}/etc/passwd << EOF
root:x:0:0:root:/root:/bin/sh
user:$5$9mJ1G1op3Q.Wr67n$nYwdPsNZduf9vE9tXvlZtAykCGrhxA2HTxQjttwS/Y.:1000:1000:user:/:/bin/sh
EOF


echo "Starting dropbear inside chroot..."
(
	chroot ${CHROOTDIR} /bin/busybox --install -s /bin
	echo "Changing password of user to foobar"
	echo "user:foobar" | chroot ${CHROOTDIR} /bin/chpasswd
	chroot ${CHROOTDIR} /bin/dropbear -F -E -B -R -g -m -p 5022
	echo "dropbear exited.. cleaning up!"
	umount ${CHROOTDIR}/dev/pts
	umount ${CHROOTDIR}/dev
	umount ${CHROOTDIR}/lib/x86_64-linux-gnu
)&