I'm also unable to mount an EFS drive from the Spark Driver.

In my setup, I use the following:

• A customer-managed VPC, with a security group allowing all TCP traffic to/from members of the same security group
• I instantiate the EFS file system in the same VPC and with the same security group. I've tried both the standard, and the one-zone EFS config.
• When I manually start an EC2 instance in the VPC, on the same security group, and in the same zone with the EFS, I can mount the drive. Tcpdump sees traffic going to the EFS server at TCP port 2049, as expected.
• When I run identical commands on the Spark Driver, the EFS mount fails. Strangely, tcpdump sees no TCP traffic sent to the EFS server at TCP port 2049. But I can telnet to the EFS address/port, and get a response, so it does not seem to be a security group problem.

These are the errors:

# mount -t efs -o tls fs-0844e1ea16eb32797:/ efs

Failed to mount fs-0844e1ea16eb32797 because the network was not yet available, add "_netdev" to your mount options

# mount -t nfs4 -o nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport 10.115.12.239:/ efs

mount.nfs4: access denied by server while mounting 10.115.12.239:/

root@1201-184524-l5k7rc6p-10-115-25-109:/tmp#

I suspect the difference is that my Spark Driver uses an instance profile, and maybe I have not configured that properly for EFS. But I am not sure, b/c I started an ec2 instance manually with the same instance profile, and EFS access worked.