Function exec is disabled. What to do?

I see the “Warning: exec() has been disabled for security reasons” message on my site. What should I do? How can I fix this?
Solution for the “exec disabled” issue

In order to eliminate this error message you need to do ONE of the following things:

Remove the exec string from the disable_functions at php.ini* file
Ask your hosting provider to remove the string above if you don’t have an access to the php.ini* file
Change hosting provider which allows the running of the exec function.