# Enabling automatic mounting on existing EC2 Linux instances
Existing EC2 Linux instances

The `/etc/fstab` file contains information about file systems. The command `mount -a`, which runs during instance start-up, mounts all the file systems listed in `/etc/fstab`. In this procedure, you will manually update the `/etc/fstab` on an Amazon EC2 Linux instance so that the instance uses the EFS mount helper to automatically remount an EFS file system when the instance restarts.

**Note**  
EFS file systems do not support automatic mounting using `/etc/fstab` with the EFS mount helper on EC2 Mac instances running macOS Big Sur or Monterey. Instead, you can use [NFS with `/etc/fstab`](nfs-automount-efs.md) to automatically mount your file system on EC2 Mac instances running macOS Big Sur and Monterey.

This method uses the EFS mount helper to mount the file system. The mount helper is part of the `amazon-efs-utils` set of tools. 

The `amazon-efs-utils` tools are available for installation on Amazon Linux and Amazon Linux 2 Amazon Machine Images (AMIs). For more information about `amazon-efs-utils`, see [Installing the Amazon EFS client](using-amazon-efs-utils.md). If you are using another Linux distribution, such as Red Hat Enterprise Linux (RHEL), manually build and install `amazon-efs-utils`. For more information, see [Installing the Amazon EFS client on other Linux distributions](installing-amazon-efs-utils.md#installing-other-distro).

## Prerequisites


The following requirements need to be in place before you can successfully implement this procedure:
+ You have already created the EFS file system that you want to be automatically remounted. For more information, see [Quick create using the console](creating-using-create-fs.md#gs-step-two-create-efs-resources).
+ You have already created the EC2 Linux instance that you want to configure to automatically remount an EFS file system.
+ The EFS mount helper is installed on the EC2 Linux instance. For more information, see [Installing the Amazon EFS client](using-amazon-efs-utils.md).

## Update the /etc/fstab file


Perform the following steps to update the /etc/fstab on an EC2 Linux instance so that the instance uses the EFS mount helper to automatically remount an EFS file system when the instance restarts.

**To update the /etc/fstab file on your EC2 instance**

1. Connect to your EC2 instance. For more information, see [Connect to your EC2 instance](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/connect.html) in the *Amazon EC2 User Guide*.

1. Open the `/etc/fstab` file in an editor.

1. For automatic mounting using either IAM authorization or an EFS access point:
   + To automatically mount with IAM authorization to an EC2 instance that has an instance profile, add the following line to the `/etc/fstab` file.

     ```
     file-system-id:/ efs-mount-point efs _netdev,noresvport,tls,iam 0 0
     ```
   + To automatically mount with IAM authorization to a Linux instance using a credentials file, add the following line to the `/etc/fstab` file.

     ```
     file-system-id:/ efs-mount-point efs _netdev,noresvport,tls,iam,awsprofile=namedprofile 0 0
     ```
   + To automatically mount a file system using an EFS access point, add the following line to the `/etc/fstab` file.

     ```
     file-system-id:/ efs-mount-point efs _netdev,noresvport,tls,accesspoint=access-point-id 0 0
     ```
**Warning**  
Use the `_netdev` option, used to identify network file systems, when mounting your file system automatically. If `_netdev` is missing, your EC2 instance might stop responding. This result is because network file systems need to be initialized after the compute instance starts its networking. For more information, see [Automatic mounting fails and the instance is unresponsive](troubleshooting-efs-mounting.md#automount-fails).

   For more information, see [Mounting with IAM authorization](mounting-IAM-option.md) and [Mounting with EFS access points](mounting-access-points.md).

1. Save the changes to the file.

**Note**  
In some cases, your EC2 instance might need to start regardless of the status of your mounted EFS file system. In such cases, add the `nofail` option to your file system's entry in your `/etc/fstab` file.

The line of code you added to the `/etc/fstab` file does the following.


| Field | Description | 
| --- | --- | 
|  `file-system-id:/`  |  The ID for your EFS file system. You can get this ID from the console or programmatically from the CLI or an AWS SDK.  | 
|  `efs-mount-point`  |  The mount point for the EFS file system on your EC2 instance.  | 
|  `efs`  |  The type of file system. When you're using the mount helper, this type is always `efs`.  | 
|  `mount options`  |  Mount options for the file system. This is a comma-separated list of the following options: [\[See the AWS documentation website for more details\]](http://docs.aws.amazon.com/efs/latest/ug/mount-fs-auto-mount-update-fstab.html)  | 
|  `0`  |  A nonzero value indicates that the file system should be backed up by `dump`. For EFS, this value should be `0`.  | 
|  `0`  |  The order in which `fsck` checks file systems at boot. For EFS file systems, this value should be `0` to indicate that `fsck` should not run at start-up.  |