recommended watchdog usage

[James Hughes]

I'm just familiarizing myself with NARD, but I'd like to make use the
watchdog to restart my app. There seems to be a dearth of information out
there about how to use it, but this page seems helpful:
https://embeddedfreak.wordpress.com/2010/08/23/howto-use-linux-watchdog/

I tried running the /sbin/watchdog command in the foreground, just as a
test, but it didn't seem to work:

root at skeleton-c7640e49:/mnt/sdcard/user> watchdog -F /dev/watchdog
watchdog: can't open '/dev/watchdog': Device or resource busy

Does this look like the correct invocation?

Many thanks, this SDK is pretty awesome so far.

Best,
James