You must be aware that the whole root filesystem is mounted as read-only, and a temporary in-memory filesystem is used as an overlay. That means that you can change anything you want on the rootfs of the BitBoxBase (not the SSD, though!), but on reboot, all changes are gone.
This is great for resilience, eg. no corruption can occur on a sudden power outage, but it’s not great for tinkering with your device.
For quick changes to the read-only filesystem, you can chroot into it:
$ sudo overlayroot-chroot INFO: Chrooting into [/media/root-ro] ... # do your stuff ... $ exit
To deactivate the overlay root filesystem, run
sudo bbb-config.sh disable overlayrootfs from the command line. After a reboot, the rootfs is mounted regularly and all changes are persistent. You can always
enable the overlayrootfs again, using the same script. Each official update overwrites the whole rootfs, however.
If you build the BitBoxBase image yourself, you can configure the option
BASE_OVERLAYROOT in build.conf.