This installation of MySQL is already upgraded to 5.7.29, use –force if you still need to run mysql_upgrade E: dpkg was interrupted, you must manually run ‘dpkg –configure -a’ to correct the problem.
The solution is:
1- Open this file for edit:
/var/lib/dpkg/info/mysql-server-5.7.postinst
2- At line # 370, comment the echo ALTER statement which would like
#echo “ALTER USER ‘root’@’localhost’ IDENTIFIED WITH ‘auth_socket’;” >> “$initfile”
(just add # to the beginning of this line to convert it to comment)
3- Save above file and start updating it will be fine