How to correct Failed global > initialization: FileNotOpen
Run as sudo. That worked for me. 


  trevor@ubuntu-s-4vcpu-8gb-lon1-01:~/opt$ sudo ~/opt/mongodb/bin/mongod
  -f ~/opt/mongodb/mongod.conf &amp; [1] 23948
   trevor@ubuntu-s-4vcpu-8gb-lon1-01:~/opt$