Answers for "raspberry pi Failed to start mongod.service: Unit mongod.service not found."

Failed to enable unit: Unit file mongod.service does not exist.

> systemctl list-unit-files --type=service
...
mongodb.service             disabled
...

Failed to enable unit: Unit file mongod.service does not exist.

> systemctl list-unit-files --type=service 
...
mongodb.service             enabled
...