Customer is on Ubuntu 16.04 and copied the mongod.service file from our docs but could not get the service to successfully run unless he included "Type = forking" under [Service]. Type of forking is recommended for daemon style services.

thomas.schubert pointed out that this is actually dependent on mongod's configuration. If mongod configuration has fork = true then the mongod.system file must also contain "Type = forking".

For more on Type see this:
https://www.freedesktop.org/software/systemd/man/systemd.service.html#Type=

We should modify our document to include this. We may also consider including PIDFile= as well although this should match with the mongod.conf otherwise things do not start/stop well.