Ttgjyuk

To prevent mysql from starting on boot:

1. Open the terminal: Ctrl+Alt+T




2. Open the mysql.conf file: nano /etc/init/mysql.conf




3. Comment out the start on line near the top of the file, the start on might be spread across two lines, so comment out both. (comment adding # at the beginning)

If you want to manually start mysql, use the following command:

service mysql start

Taken liberally from here.

Since 15.04 you can simply do:

sudo systemctl disable mysql

Things have changed quite a bit in Ubuntu now. I think from version 11 onwards.
MySQL is handled by Upstart while Apache still uses traditional SysV init scripts

For MySQL, you can use the new override feature in Upstart to modify the starting behaviour:

sudo echo "manual" >> /etc/init/mysql.override

For more info, see the section "Disabling a Job from Automatically Starting" in the Upstart Cookbook.

As Apache still uses the traditional SysV init scripts you can use

sudo update-rc.d -f apache2 remove

to remove the links from /etc/rcX.d or, alternatively use

sudo update-rc.d apache2 disable

which "disables" the script by changing it from a start script to a stop script. This is reversible by

sudo update-rc.d apache2 enable

Most of this information I got from here: https://askubuntu.com/a/40077/24678

Or if your really laze like me you could just open a Terminal session and then type:

sudo perl -pi.orig -e 's/starts+on/#starts+on/' /etc/init/mysql.conf && sudo perl -pi.orig -e 's/ands+/#and/g' /etc/init/mysql.conf

You can then just issue a reboot command then your system will boot-up without mysql started.

Actually, there is also another method to accomplish this, via the sysv-rc-conf tool.

You can install it by typing

sudo apt-get install sysv-rc-conf

It allows you to take control over all available services, including running/stopping them in place and configuring services' operation per runlevel.

Edit: You have to run tis tool as root:

sudo sysv-rc-conf

You can use chkconfig tool package

$ chkconfig --level 345 mysqld off

In Ubuntu 18.04, sudo systemctl disable mysql will prevent mysql-server from autostarting on boot.

For linux, there are 3 main init systems: Systemd, Upstart and SysV. Although nearly all Linux systems run on Systemd. The other two init systems might also co-exist in your system.

For Systemd, use command sudo systemctl disable mysql;

For Upstart, use echo manual >> /etc/init/mysql.override;

For SysV, run the following command sudo update-rc.d mysql disable

If you'd like to find which init system is running on your server, please read this answer.