facing ERROR
bash-4.4# mongod -f mongod_2.conf
about to fork child process, waiting until server is ready for connections.
forked process: 368
ERROR: child process failed, exited with error number 48
To see additional information in this output, start without the “–fork” option.
One of the following:
Hi ,
Even I am facing same issue , but none of the 2 options are true for me.
Anything else I am missing on?
So far what I have observed is that this issue arises when I start the 3rd mongod instance , may be the memory on the host is not enough , not sure, but this is restricting the completion of this lab .
MongoDB team kindly guide here, since I have completed M103 module. Only this lab is pending and this issue is preventing me from getting my completion certificate! 
Post a screenshot of the whole IDE.
Show all 3 configuration files.
Show output of the command ps -aef | grep [m]ongo.
If you are getting the same error 48 have you run without --fork as suggested
It would give more details on why it failed or check mongod.log
I was able to deploy the RS . The issue was , dbpath in 2 config files were same , hence it was not allowing to launch one of the instance.
Thanks for your help.