Create cache file within alpine chroot

chroot_cache.sh

#!/bin/sh

WORLD=/etc/apk/world
ALPINE_RELEASE=3.9.4

echo "Running make_cache"

echo "alpine-base" > ${WORLD}
echo "avahi" >> ${WORLD}
echo "dbus" >> ${WORLD}
echo "docker" >> ${WORLD}
echo "openssh" >> ${WORLD}
echo "wireless-tools" >> ${WORLD}
echo "wpa_supplicant" >> ${WORLD}

DIR=$(pwd)
mkdir /tmp/cache
ln -s /tmp/cache /etc/apk/cache
apk update && apk cache -v sync
cd /tmp
tar cvzf cache-${ALPINE_RELEASE}.tar.gz cache
cp cache-${ALPINE_RELEASE}.tar.gz ${DIR}/
echo "Done"
exit

chroot_make_cache.sh

    apt-get update
    wget https://raw.githubusercontent.com/alpinelinux/alpine-chroot-install/v0.10.0/alpine-chroot-install \
        && echo 'dcceb34aa63767579f533a7f2e733c4d662b0d1b  alpine-chroot-install' | sha1sum -c \
        || exit 1
    chmod +x alpine-chroot-install
    apt-get install qemu-user-binfmt -y
    ./alpine-chroot-install -b v3.9 -a armhf -m https://mirror.xtom.com.hk/alpine/
    chmod +x chroot_cache.sh
    /alpine/enter-chroot ./chroot_cache.sh