I have struggled in this problem for quite a long time. I have made a persistent Ubuntu Live USB using Usb-Creator build in the Ubuntu. I have then made a 4GB image but the following problem happens.
By using some time, the /cow directory's space is being eaten gradually and finally ate up all spaces, at that stage, I cannot even login to my ubuntu account.
I have just install PHP+MySQL+Webmin+Chromium and nothing else more, is there any way to check which process continues to eat up spaces gradually?
Appreciate for any advice
Persistent storage on Ubuntu live USB installation tends to eat a lot of space by time. Cow directory is full because system automatically saves all the changes you made. Ubuntu is simply not intended to be used like that for a long time.
Puppy Linux is way more suitable for your needs since it is originally created to live on USB drive forever. It supports all the software you need and there are numerous software installation instructions like this