Oh, I missunderstood. I thought you did the dd command. You installed,
using Ubiquity, to the flash drive? That should work, and be
persistent. Not sure what might be happening there.
To add the casper filesystem, write the Trisquel image with dd, as you
had done before, from another GNU/Linux. after it's done, use disk
utility to find your flash drive onto which you did the dd command. Or,
you can use gparted. After the 'squasfs' filesystem on the flash drive,
there should be additional space that is free. make a new partition,
using all this free space. You'll be shown options for boot flags and
filesystem type. The new partition does not need to be bootable, but
does need to formatted as ext4 (maybe it says 'Linux'? and be named
casper-rw.
There are two tools that take care of all this for you, one being the
startup disk creator found in Trisquel, another being unetbootin from a
repository called ppa:gezakovacs. Add this to your sources list, then
install unetbootin. You can launch unetbootin with a gui or commandline
options. Homepage: unetbootin.sourceforge.net. I've used this tool
many times, with success, from the commandline.
