I am mostly ignorant about Ubuntu and Linux.
Here is my sequence of thoughts:
I would like to have a "fast boot" PC (boot < 100,150 secs) and lightly customized to my needs to be able to do my banking ops and manage my passwords.
For security reason, I need to run a --most of the time read only-- OS, (preferably) open source. The only read-only enforcement mechanism that I trust is a hardware switch (not quite safe, I know. I have to trust the builder). I would put the OS on an external usb drive.
At this point, my question is preliminary: Today, is there a easy way (for some one who has worked in IT in the past) to install a custom (custom not once for all) Linux OS on an external drive with a read only switch? What would it allow or, on the contrary, what would it not be able to do?
Custom not-once-for-all because I want to be able to take advantage of new features or new packages or security patches, to be able to install them r/w and then to use them read-only.
Thanks for your help and ideas. LB
PS I have made some research but I haven't seen any real answer. And answers might change over time. Question close to this one: xubuntu custom read only image