Can't resolve DNS name of EFS while mounting it on red hat ec2 instances using putty

Question

I am having an issue where I am unable to mount my EFS on red hat ec2 instance using the DNS names. It throws the error

mount.nfs4: Failed to resolve server us-east-1a.fs-c2aXXXX.efs.us-east-1.amazon
aws.com: Name or service not known

I am following the instructions provided by AWS. I tried below two ways to do it and both throw the same above error. I can confirm that the DNS names are correct.

1st:

mount -t nfs4 -o nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport fs-c2aXXXX.efs.us-east-1.amazonaws.com:/ efs

2nd:

mount -t nfs4 -o nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2 $(curl -s http://169.254.169.254/latest/meta-data/placement/availability-zone).fs-c2a7XXXX.efs.us-east-1.amazonaws.com:/ /efs

However, if I use IP instead of DNS names, I am able to mount it just fine. So below command works.

mount -t nfs4 -o 
nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport 10.38.X.XX:/ /efs

I am fine with using IP instead of DNS as long as I am able to mount it.

Now my issue is as soon as I stop and start the instance again, my mount is gone. Even after I add the below entry to the /etc/fstab, it doesn't do auto mount.

10.38.X.XXX:/ /efs efs defaults,_netdev 0 0

Can someone please help me in either resolving the issue with DNS or tell me how to auto mount using IPs?

Answer 1

To attach to EFS from the command line use this as your template, replacing fs-12345678 with your id:

$ sudo mount -t efs fs-12345678:/ /efs

Use this in your /etc/fstab (do not add .efs.us-east-1.amazonaws.com after it)

fs-12345678:/ /efs efs vers=4.1,rw,tls,_netdev,relatime,acl,nofail 0 0

The fstab version also turns on encryption for data transport. Check out the resource for more information

Resources

https://docs.aws.amazon.com/efs/latest/ug/mounting-fs.html https://docs.aws.amazon.com/efs/latest/ug/troubleshooting-efs-mounting.html#automount-fails

Answer 2

If you have opened all security groups, network ACLs, confirmed that you are in a valid AZ and still not working; probably the VPC you created doesn't have DNS hostnames enabled, validate that you have this setting:

The default VPC that comes with your account has this enabled, others don't.