Moving MySQL databases/folder to another disk I want to separate MySQL database from the OS (Ubuntu) disk by moving the entire database to an exclusive HDD (M.2), and update the database folder in my.cnf.

My question is: when the MySQL folder is on a separate disk, can I safely format the OS disk and install a fresh Ubuntu (and MySQL)?

Is it OK to install a fresh MySQL and simply point to the existing MySQL folder on a different disk in the my.cnf of freshly installed MySQL?

OR the best practice is to restore the databases from a dump after a fresh install, though the database is still available in the machine?
Yes, you can here is the steps to do it.
backup:

# service mysqld stop
# cd /var/lib/mysql
# tar -cvzf /tmp/mysql-backup.tar.gz ./*
# service mysqld start


restore:

# service mysqld stop
# cd /data/mysql
# tar -xvzf /tmp/mysql-backup.tar.gz
# service mysqld start


Notes: 


Cold backup will not work if you try to restore it in older versions of MySQL it will be better if you use the same version.
You need to make sure new directory is owned by MySQL user and it has the needed permission
New datadir is accurate inside my.cnf