Why did the config file revert to default after updating the mysql package?

Question

linux

Good afternoon!
Faced with an unpleasant and strange problem for me.
On one of the servers, it turned out that automatic updates of security packages were not configured for half a year.
And when the problem was discovered, unattended-upgrade was installed and launched, after which it updated all the security-related pacts, including mysql
. As it turned out after the update, the my.cnf configuration file in which everything was well configured for the left just disappeared and the file returned to the starting value.
Perhaps someone has come across this, or knows what the reason is and how important it is to avoid it in the future.
I would be very grateful for any help!
Thanks in advance!
And have a nice day!

Answer 1

https://habr.com/ru/company/flant/blog/330406/
well, for example, read here. In general, you yourself asked the system so)

Answer 2

It asks what to do with the config, leave the current one or write down the one provided by the package maintainer.

Answer 3

That's why I basically backup /etc every day ;)