update-rc.d:tldr:458ed

This command is used to disable the auto-start of the MySQL service during system boot.

Here is a breakdown of the command:

• update-rc.d: This is the command to manage the initialization script links for system services.
• ${mysql}: This is a variable that represents the name of the MySQL service. It is likely defined previously in the script or by the user.
• disable: This is the argument passed to update-rc.d to specify that the specified service should be disabled at startup.

Overall, this command will remove the symbolic links in the appropriate runlevel directories that enable the automatic start of the MySQL service. Disabling it means that the MySQL service will not be automatically started when the system boots up.