I'll be honest... I'm extremely new to the Nimble community and not aware of CLI/API capabilities yet. If you can ssh from Linux directly to Nimble then that would obviously be your choice.
Forgot to add... ping me offline at email@example.com if you need some help writing this. Both PowerShell and Bash.
Check out the excellent script written by Tom Dau:
It specifically pertains to Oracle but the genesis of the operations is identical - Tom's script puts Oracle into and out Archive logmode in order to get the consistency but you should be easily able to substitute that for the MySQL equivalent or the shutdown/restart of the service.
I wrote my own snapshot utility similar to the oracle one. I already have custom backup scripts for mysql so I added this process to the same project. The basic idea goes like this:
* process on DB server locks database
* forked process starts snapshot on nimble
* after snap DB tables are unlocked
I posted the code here. Feel free to take a look.