The following tutorial will show you one way to create a writable Casper partition on your USB flash drive. The benefit of using a casper-rw partition as opposed to a casper-rw block file is that you can expand your persistent storage beyond 4GB. This is very useful if you have a flash drive that is 8GB or larger and you want to use all of its remaining space for persistent storage. The drawback is that Windows will not see the secondary casper-rw partition (in Windows, your drive will appear to be smaller than it is).
This tutorial assumes that you have already created a bootable USB Flash Drive that contains Ubuntu or an Ubuntu based Live Distro like Xubuntu, Kubuntu, Linux Mint, etc. You should delete any existing casper-rw or writable file from the drive or directory to free up all available space before proceeding.
Restart your Computer, booting from your Ubuntu based Live USB
Select and run GParted from your list of Applications.
NOTE: If GParted is not installed, open a terminal and type;
sudo apt-get install gparted
then press Enter. Then, once the installation has finished, type;
and press Enter.
Once you have GParted up and running;
1. Select your USB device from the drop-down.
2. Then Unplug the USB drive from your PC and then plug it back in.
3. Right mouse click within the green box and choose Resize/Move
Now we need to resize the first partition that contains your Live OS;
1. Drag the size down to what you want to limit for the first partition.
2. Then click Resize/Move.
Next select the unallocated entry, right mouse click and select New
From the Create New Partition Window that appears;
1. If your Ubuntu/Mint ISO version is 20+ use writable for the label, otherwise type casper-rw
2. Then click Add.
Now click the Checkmark to Apply all operations
Once the pending operations have completed, simply close the Window and restart Booting from your Flash Drive
If all went well, you should now be running your Ubuntu or Ubuntu based Live Distro from your Flash Drive that now uses a second ext2, ext3, or ext4 partition instead of a file for storing your changes.
Keep in mind that you need to use the persistent cheat/boot code to ensure that the operating system boots up with persistence.