After much searching on forums without success, I seek the wisdom of this group.

I have a weird problem that may just be permissions but I suspect it is deeper than that.

I am not new to Linux but cannot profess to be competent either. I recently installed a bootable version of the latest V20 Cinnamon on USB (32bg)

Everything runs well and the updaters run and install as you would expect and complete as normal.

However, if I restart Linux it returns to the new clean installation and the updates and apps like Skype have not been applied. I can run the updater again and repeat the exercise without any error but the newly updated Linux has dumped the lot...

Any thoughts would be gratefully received.

Sounds like a liveUSB running in non-persistent mode Tell us how (in minute detail) how you did this install - post a link if you followed something online.

would be nice to know exactly what did you install. I guess you put a live CD onto the pendrive and that cannot be updated (read only).

Thanks for your replies.

I am installing linuxmint-20-cinnamon-64bit.iso from the official repository onto a 32gb SanDisk Extreme thumb drive. I have used a variety of installers (BalelaEtcher on Mac) Mac Linux USB Loader and a couple of other Linux USB installers.

I have formatted the USB to FAT32 as that is the only format the installers recognise. On one install I selected Mac OS extended journaled but the same issue existed that resulted in the installed Linux apparently successfully updating but then resetting to default install and all updates lost.

I do believe as in the post above it is a write to disk issue but have no idea what I am doing (or not doing) to cause this. Perhaps I should not use the installers and do the transfer to USB manually?

I can guess only: you did not install this iso onto the pendrive, but copy it.
This ISO is bootable and will start an OS, but next time you will boot the same iso image again and again. You cannot update it. If I need to guess there is an install icon on the desktop (when booted).
You need to really install the Mint onto a pendrive or hdd. The first step is to make a bootable pendrive - to be able to install it. This is what you made already. You need to click on the mentioned install icon and select another device. So it means you need to use 2 usb sticks one for the install image and the second as the target device (if you wish to install it on a thumb drive).