Failed to start of service MongoDB community4.2 using Homebrew in Mac OS Mojave 10.14 Error message while starting the mongoDB service. 
Error: 


  Permission denied @ rb_sysopen -
  /Users/syedahmed/Library/LaunchAgents/homebrew.mxcl.mongodb-community.plist


I installed/reinstall the mongoDB couple times. 
But I am getting same problem 


  " error : permission denied"


I am using the community@4.2 edition in Mac OS Mojave 10.14

I have tried different ways after reading suggestions in stack overflow but nothing has worked.

I have installed following the instruction from mongoDB. 

The services doesn't start. 

how to config the username and password using config?  I am not sure.

while installing from brew it did not ask for config any password or username.

brew services start mongodb-community@4.2

if I start service typing just:  mongo
Following error message comes:


  MongoDB shell version v4.2.0 connecting to:
  mongodb://127.0.0.1:27017/?compressors=disabled&amp;gssapiServiceName=mongodb
  2019-09-01T23:23:31.392-0400 E QUERY [js] Error: couldn't connect to
  server 127.0.0.1:27017, connection attempt failed: SocketException:
  Error connecting to 127.0.0.1:27017 :: caused by :: Connection refused
  : connect@src/mongo/shell/mongo.js:341:17 @(connect):2:6
  2019-09-01T23:23:31.397-0400 F - [main] exception: connect failed
  2019-09-01T23:23:31.397-0400 E - [main] exiting with code 1 –
use code below before mongo

sudo brew services start mongodb-community