Umount, not mount a 2nd time ...

alpine-install-on-disk.sh

@@ -25,7 +25,7 @@ rootfs_tmpdir=$(mktemp -d)
 rootfs_url="http://dl-cdn.alpinelinux.org/alpine/v$MAJOR_VERSION/releases/x86_64/$IMAGE"
 
 run_root () {
-    sudo chroot $rootfs_tmpdir
+    sudo chroot $rootfs_tmpdir /usr/bin/env \
         PATH=/sbin:/bin:/usr/sbin:/usr/bin \
         /bin/sh -c "$*"
 }
@@ -95,7 +95,7 @@ run_root grub-install --target=i386-pc ${DISK}
 # Cleanup
 run_root rm -f /etc/resolv.conf
 for dir in dev proc sys; do
-    sudo mount --bind /${dir} ${rootfs_tmpdir}/${dir}
+    sudo umount ${rootfs_tmpdir}/${dir}
 done
 sudo umount  $rootfs_tmpdir