# Mounting on Amazon EC2 with a DNS name
<a name="mounting-fs-mount-cmd-dns-name"></a>

**Note**  
Prior to mounting your file system, you need to add a rule to the mount target security group that allows inbound NFS access on port 2049 from the EC2 security group. For more information, see [Using VPC security groups](network-access.md).
+ **File system DNS name** – Using the file system's DNS name is your simplest mounting option. The file system DNS name automatically resolves to the mount target’s IP address in the Availability Zone of the connecting Amazon EC2 instance. You can get the DNS name from the console, or if you have the file system ID, you can construct it using the following convention.

  ```
  file-system-id.efs.aws-region.amazonaws.com
  ```
**Note**  
 DNS resolution for file system DNS names requires that the Amazon EFS file system has a mount target in the same Availability Zone as the client instance. 
  + Using the file system DNS name, you can mount a file system on your Amazon EC2 Linux instance with the following command.

    ```
    sudo mount -t nfs -o nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,noresvport file-system-id.efs.aws-region.amazonaws.com:/ /efs-mount-point
    ```
  + Using the file system DNS name, you can mount a file system on your Amazon EC2 Mac instance running a supported macOS version (Big Sur, Monterey, Ventura) with the following command.

    ```
    sudo mount -t nfs -o nfsvers=4.0,rsize=65536,wsize=65536,hard,timeo=600,retrans=2,noresvport,mountport=2049 file-system-id.efs.aws-region.amazonaws.com:/ /efs
    ```
**Important**  
You must use `mountport=2049` in order to successfully connect to the EFS file system when mounting on EC2 Mac instances running support macOS versions.
+ **Mount target DNS name** – In December 2016, we introduced file system DNS names. We continue to provide a DNS name for each Availability Zone mount target for backward compatibility. The generic form of a mount target DNS name is as follows.

  ```
  availability-zone.file-system-id.efs.aws-region.amazonaws.com
  ```
**Note**  
Mount target DNS name resolution across Availability Zones is supported.

  In some cases, you might delete a mount target and then create a new one in the same Availability Zone. In such a case, the DNS name for that new mount target in that Availability Zone is the same as the DNS name for the old mount target.

You can view and copy the exact commands to mount your file system in the **Attach** dialog box.

**To view the mount commands for your file system**

1. In the Amazon EFS console, choose the file system that you want to mount to display its details page.

1. To display the mount commands to use for this file system, choose **Attach** in the upper right.

   The **Attach** screen displays the exact commands to use for mounting the file system.

1. The default **Mount via DNS** view displays the command to mount the file system using the file system's DNS name when mounting with the EFS mount helper or an NFS client.

For a list of AWS Regions that support Amazon EFS, see [Amazon Elastic File System ](https://docs.aws.amazon.com/general/latest/gr/rande.html#elasticfilesystem-region) in the AWS General Reference.

To be able to use a DNS name in the `mount` command, the following must be true:
+ The connecting EC2 instance must be inside a VPC and must be configured to use the DNS server provided by Amazon. For information about Amazon DNS server, see [DHCP option sets in Amazon VPC](https://docs.aws.amazon.com/vpc/latest/userguide/VPC_DHCP_Options.html) in the *Amazon VPC User Guide*. 
+ The VPC of the connecting EC2 instance must have both **DNS Resolution** and **DNS Hostnames** enabled. For more information, see [ DNS attributes for your VPC](https://docs.aws.amazon.com/vpc/latest/userguide/vpc-dns.html#vpc-dns-viewing) in the *Amazon VPC User Guide*. 
+ The connecting EC2 instance must be inside the same VPC as the EFS file system. For more information on accessing and mounting a file system from another location or from a different VPC, see [Prerequisites](mounting-fs-mount-helper-direct.md#efs-onpremises) and [Tutorial: Mount a file system from a different VPC](efs-different-vpc.md).

**Note**  
We recommend that you wait 90 seconds after creating a mount target before you mount your file system. This wait lets the DNS records propagate fully in the AWS Region where the file system is.