flashctl question Bigsur board

We had the filesystem writable; - create directories in root (/home)
new we get an error “Function not implemented” for any attempt to write to
the filesystem
Our bootimage size is now greater than 4M.

What statements need to be added to bigsur-flash.build to get this behavior
?

I am able to create another partition /dev/fs0p1 -o5M -l64M. This is
available as /fs0p1. Is it possible to mount /dev/fs0p1 as / so the file
system looks uniform. We were looking to copy a newer version of some
programs on top of the existing one (mask).

Thanks,
Sudarshan

I am able to create another partition /dev/fs0p1 -o5M -l64M. This is
available as /fs0p1. Is it possible to mount /dev/fs0p1 as / so the file
system looks uniform. We were looking to copy a newer version of some
programs on top of the existing one (mask).

try mounting, unmount, and mount again:
flashctl -v -p /dev/fs0p1 -n / -m
flashctl -v -p /dev/fs0p1 -n / -u
flashctl -v -p /dev/fs0p1 -n / -m