These aren't metaphors, though. For example, a "parent process" uses the term "parent" that's defined as "a source or origin of a smaller or less important part," not "a father or mother," or one of the other half-dozen definitions

"Kill" is definitely a metaphor. A more literal phrase would be "force stop".

One of the definitions of "kill" is "to put an end to or cause the failure or defeat of (something)." This is not a metaphor either.

One of the definitions of "slave" is "A device (such as a secondary flash or hard drive) that is subject to the control of another". Is that not a metaphor either?