Answer by Rinzwind for MySQL 5.5 Update to MySQL 5.7

This worked for me:

wget https://dev.mysql.com/get/mysql-apt-config_0.8.10-1_all.debsudo gdebi mysql-apt-config_0.8.10-1_all.debsudo apt-get updatesudo apt-get install mysql-server

The 2nd command will ask for input:

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After picking 5.7 choose "apply"

$ mysql --versionmysql  Ver 14.14 Distrib 5.7.8-rc, for Linux (x86_64) using  EditLine wrapper

Don' forget to run mysql_upgrade after installation to upgrade system tables and restart server, following MySQL Upgrading guide.

$ mysql_upgrade

or

$ sudo mysql_upgrade -u root -p

And restart mysql

sudo service mysql restart