Problems to update Knoppix

[Capricorny]

What's wrong with apt-get and Knoppix? I am new with the recent Knoppix, please let me know

IMHO, nothing is wrong with Knoppix and apt-get. As to doing apt-get upgrade, that should IMHO be considered potentially dangerous in most Debian configurations. It may go well, but quite often, it doesn't. There are many reasons why. One of the most important is that in practice, a running system will often have some packages not native to the release mixed in - like Knoppix.

I have found one safe way to proceed, "everywhere Debian", to be

sudo apt-get update && sudo apt-get -s upgrade

Then I get a report of the upgradable packages. In some cases, I will consider the risk of trouble so small that I proceed with the ordinary upgrade, but most often, I will start with some selected, important packages. I'm not sure how much is won with a huge upgrade within a Knoppix release, even if it should be possible. Like now with Debian 8.3 -> 8.4. I rather do the absolutely necessary updates and wait for the next Knoppix release, and that has worked fairly well over the years.

[utu]

I have found one safe way to proceed, "everywhere Debian", to be

sudo apt-get update && sudo apt-get -s upgrade

I think your posts 9 & 10 are an excellent treatment of the hazards of upgrading.
I would only add that in the present context of this thread, that
the -s in your prescription is a pretty important detail as well, meaning 'simulate'.