/ # umount /target
/ # ls /target/
/ # DATA_PARTITION=/dev/block/mmcblk0p25
/ # rm -rf /data
rm: can't remove '/data': Device or resource busy
/ #     rm -rf /target
/ #
/ #     mkdir /data
mkdir: can't create directory '/data': File exists
/ #     mkdir /target
/ #
/ #     mount $DATA_PARTITION /data
mount: mounting /dev/block/mmcblk0p25 on /data failed: Device or resource busy
/ #     mount --bind /data/.stowaways/${DEFAULT_OS} /target
mount: mounting /data/.stowaways/ on /target failed: No such file or directory
/ #     mkdir /target/data # in new fs
/ #     mount --bind /data /target/data
/ # switch_root /target /lib/systemd/systemd
BusyBox v1.21.1 (2016-05-12 01:27:53 UTC) multi-call binary.

Usage: switch_root [-c /dev/console] NEW_ROOT NEW_INIT [ARGS]

Free initramfs and switch to another root fs:
chroot to NEW_ROOT, delete all in /, move NEW_ROOT to /,
execute NEW_INIT. PID must be 1. NEW_ROOT must be a mountpoint.

        -c DEV  Reopen stdio to DEV after switch

/ #