Same issue here, mysql file is 0kb inside backup.
I suspect it’s because of Upgrading Mariadb manually as described here:
I did this for four of my servers, and then this issue appeared. I have no idea how to solve it.
An update with some findings:
Doing the backup manually with the following commands is also creating the same 0KB SQL file:
mysql -u user -p database > backup.sql
mariadb -u user -p database > backup.sql
The only command that is actually doing backup properly is:
mysqldump -u user -p database > backup.sql