How do I change the machine name of a field once it's been created I spaced out while typing the field name an now the machine name is not what I wanted it to be. I know it's just an annoyance. but I'm wondering if there is some way to alter the machine name of a field once it is created.

I suppose this leads me into the second part of my question. if I created a field, and it is no longer being used, how do I go about deleting it, does this have to be done from the database, or can it be done somewhere in the UI.
My procedure is to use drush to clone the field first, then copy the field data with DB queries into the new field table. After I verify the contents of the cloned field, I delete the original field. 

I do it this ways because I think the drush method of cloning fields will always be at least as reliable as any cloning code I might craft myself, the data copy query is pretty simple, and I get to check the new field before deleting the original.


drush field-clone field_my_field field_my_field_clone
Insert rows into field_my_field_clone, e.g., INSERT field_my_field_clone SELECT * FROM field_my_field;
Verify the contents of field_my_field_clone.
Delete the field using the UI, e.g., admin/structure/types/manage/my-content-type/fields