Trying to configure firmware updater on a rpi 3, octoprint v1.3.8, for a prusa mk3. I installed avrdude and when I click test it says path doesn't exist:
But it does exist there:
I'm sure I'm doing something stupid...hoping one of you can tell me what it is! 
Anyone? Bueller? Bueller?
I'd check the permissions (ls -l). You are comparing the owner and the user (pi) to determine which field of the permissions is applied, and then what are the permissions in that field.
I'd also suggest to take a look into / share the logs, they might contain more information.
Permissions are:
-rwxr-xr-x 1 root root 395660 Jul 7 2015 /usr/bin/avrdude
Tried chmod 777 on it with no effect (as expected)
Log file:
octoprint (3).log (75.8 KB)
Things you can ignore: me starting the bed visualizer while I had something still on the print bed, der!
018-05-03 01:12:49,612 - octoprint.util.comm - WARNING - Received an error from the printer's firmware: Printer halted. kill() called!
And a short network outage today @ 2018-05-03 22:16:28,043
I uninstalled/reinstalled the firmware plugin tonight but I don't see that in the log.
After using postman to test the api used by the plugin I realized I had a SPACE before /usr/bin/avrdude
Is there a facepalm emoji on here?
I've lost count of the number of times I've been bitten by spaces before / after command lines, when copying them from a terminal. So much so that now whenever I paste them I hit home and end to see if there are any spaces. You're not alone.
I am still stuck on this step. Your post helped me at least find the path.
when I type the path in now I get an error.
My path on my raspberry pi is exactly the same as yours.
This is what I typed for Path to avrdude
/usr/bin/avrdude /etc/avrdude.conf /usr/share/man/man1/avrdude/1/gz
Any ideas.
so I got it!!!!
It just be
usr/bin/avrdude
Hazzah!
Ended up here as I couldn't get the path to work and then checked for spaces - that was the issue! hahaha
