Cant mount with EFS Mount Helper

Question

I'm experiencing difficulty mounting EFS to my EC2 instance using the EFS Mount Helper/DNS, it hangs indefinitely. However, the IP Address mount works fine.

I've made sure that all prerequisites are met:

1. My VPC has both DNS hostnames enabled.
2. My EC2 and EFS are in the same VPC and Region (ap-southeast-5).
3. The Amazon EFS mount helper and botocore are installed on the EC2 instance.
4. The security groups are configured correctly with the EC2 SG having an outbound NFS rule 2049 to the EFS SG, and the EFS SG having an inbound NFS rule 2049 from the EC2 SG.

![1](/media/postImages/original/IML82hIh66Tkqnds7Msuxplg)
![2](/media/postImages/original/IMJ0Vzzur4QWCH5nmZ0L96-w)
![3](/media/postImages/original/IM_4CTVzOFQlOAIWkmnA6HHg)
![4](/media/postImages/original/IMUeWb3_pDR1SmAIvDQLL2Yg)
![5](/media/postImages/original/IMKxBVaw8BR8yJ_PJLfFGhrw)

re:Post Agent · Accepted Answer

Based on the information you've provided, it seems you've covered most of the common issues that could prevent EFS from mounting using the EFS Mount Helper. However, there are a few additional points to consider:

1. DNS Propagation: After creating a new mount target, it's recommended to wait at least 60 seconds before attempting to mount the file system via DNS. This allows time for the DNS records to fully propagate within the AWS Region where your file system resides.

2. Mount Target State: Ensure that the lifecycle state of your mount target is "available" before attempting to mount.

3. Network Connectivity: Verify that your EC2 instance can resolve the EFS DNS name and reach the mount target. You can test this using tools like `nslookup` and `telnet`.

4. EFS Mount Helper Version: Make sure you're using the latest version of the EFS mount helper. Older versions might have issues that have been resolved in newer releases.

5. Mount Command: Double-check your mount command. A typical mount command using the EFS mount helper looks like this:

```
sudo mount -t efs -o tls fs-abcd123456789ef0 /mnt/efs
```

Ensure you're using the correct file system ID and mount point.

6. EC2 Instance Type: Some older or smaller instance types might have issues with the default rsize and wsize values used by the EFS mount helper. You could try specifying smaller values in your mount command:

```
sudo mount -t efs -o tls,rsize=1048576,wsize=1048576 fs-abcd123456789ef0 /mnt/efs
```

7. Network File System Option: When mounting your file system automatically (e.g., via /etc/fstab), make sure to use the `_netdev` option. This identifies the file system as a network file system and ensures it's initialized after the instance starts its networking.

If you've verified all these points and are still experiencing issues, you might want to check the system logs for any error messages related to the mount process. The EFS mount helper logs to syslog, so you can check `/var/log/syslog` or `/var/log/messages` depending on your Linux distribution.  
**Sources**  
[Mounting EFS file systems - Amazon Elastic File System](https://docs.aws.amazon.com/efs/latest/ug/mounting-fs.html)  
[Mounting EFS file systems using the EFS mount helper - Amazon Elastic File System](https://docs.aws.amazon.com/efs/latest/ug/efs-mount-helper.html)  
[Prerequisites for using the EFS mount helper - Amazon Elastic File System](https://docs.aws.amazon.com/efs/latest/ug/mount-helper-prerequisites.html)  
[Mount settings used by EFS mount helper - Amazon Elastic File System](https://docs.aws.amazon.com/efs/latest/ug/mount-helper-setting.html)

Cant mount with EFS Mount Helper

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