how to prevent *.list files from getting overwritten?

Question

Following the accepted answer to this question, I have adjusted the ppa entry for geogebra to the following entry:

deb [signed-by=/usr/share/keyrings/geogebra.gpg] http://www.geogebra.net/linux/ stable main

This works very well, however occasionally the file /etc/apt/sources.list.d/geogebra.list seems to get overwritten and reverted to the old version:

deb http://www.geogebra.net/linux/ stable main

When is this file overwritten? How can I prevent this, without reducing the security level (meaning: I want the particular key to be usable only for the particular ppa and software)?

I am on (K)Ubuntu 23.10.

Answer 1

Working around the problem:

You can make the file immutable:

sudo chattr +i /etc/apt/sources.list.d/geogebra.list

You can change the file name to geogebra-classic.list. The other file will provide a warning when using apt.

But to solve the root cause of the problem you need to check the running script on your system, crontab, custom systemd services...