[justinsaccount]

What is the "it" that you did?

Changing a string like 'foo=yes' to 'foo=no ' would be easy enough - as long as the filesystem does not checksum data.

Adding multiple lines to multiple files is not going to work very well.

[gregwtmtno]

I've modified configuration files on a FreeBSD filesystem image with a hex editor to cause it to obtain a dhcp lease and allow password ssh login for the default account. (Linux cannot read/write to the default FreeBSD filesystem.)

This allowed me to set up the RPi headless and keyboardless.

Of course the filesystem was dirty, but it's nothing an fsck couldn't solve.