Amazon Elastic File System
User Guide

Mounting Automatically

You can use the file fstab to automatically mount your Amazon EFS file system whenever the Amazon EC2 instance it is mounted on reboots. There are two ways to set up automatic mounting. You can update the /etc/fstab file in your EC2 instance after you connect to the instance for the first time, or you can configure automatic mounting of your EFS file system when you create your EC2 instance.

Updating an Existing EC2 Instance to Mount Automatically

To automatically remount your Amazon EFS file system directory when the Amazon EC2 instance reboots, you can use the file fstab. The file fstab contains information about file systems, and the command mount -a, which runs during instance startup, mounts the file systems listed in the fstab file.


Before you can update the /etc/fstab file of your EC2 instance, make sure that you've already created your Amazon EFS file system and that you're connected to your Amazon EC2 instance. For more information, see Step 2: Create Your Amazon EFS File System in the Amazon EFS Getting Started exercise.

To update the /etc/fstab file in your EC2 instance

  1. Connect to your EC2 instance, and open the /etc/fstab file in an editor.

  2. Add the following line to the /etc/fstab file.

    mount-target-DNS:/ efs-mount-point nfs4 nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2,_netdev 0 0

    If you want to copy the contents of your /etc/fstab file between EC2 instances in different Availability Zones (AZ), we recommend that you use the file system DNS name. You shouldn't copy the /etc/fstab file between AZs if you're using the mount target DNS name, because then each file system will have a unique DNS name for each Availability Zone with a mount target. For more information about DNS names, see Mounting on Amazon EC2 with a DNS Name.

  3. Save the changes to the file.

Your EC2 instance is now configured to mount the EFS file system whenever it restarts.


If your Amazon EC2 instance needs to start regardless of the status of your mounted Amazon EFS file system, you'll want to 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


The Domain Name Server (DNS) name for the file system that you want to mount. This is the same value used in mount commands to mount the subdirectory of your EFS file system.


The mount point for the EFS file system on your EC2 instance.


The type of file system. For EFS, this type is always nfs4.

mount options

Mount options for the file system. This is a comma-separated list of the following options:

  • nfsvers – Identifies the version of NFS that will be used. We recommend 4.1 as the value for this option.

  • rsize – Defines the size of the chunks for reading data between your client and the file system in the cloud. We recommend 1048576 as the value for this option.

  • wsize – Defines the size of the chunks for writing data between your client and the file system in the cloud. We recommend 1048576 as the value for this option.

  • hard – Specifies that the local applications using a file on the file system should stop and wait for the file system to come back online if Amazon EFS is temporarily unavailable.

  • timeo – Specifies the amount of time, in tenths of a second, that the NFS client waits for a response before it retries a request to the file system in the cloud. We recommend 600 deciseconds as the value for this option.

  • retrans – Specifies the number of times the NFS client should retry a request. We recommend 2 as the value for this option.

  • _netdev – This is used to prevent the Amazon EC2 instance’s kernel from mounting the file system before the instance has network connectivity.

For more information, see Additional Mounting Considerations.


A nonzero value indicates the file system should be backed up by dump. For EFS, this value should be 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 startup.

Configuring an EFS File System to Mount Automatically at EC2 Instance Launch

You can configure an Amazon EC2 instance to mount your Amazon EFS file system automatically when it is first launched with a script that works with cloud-init. You add the script during the Launch Instance wizard of the EC2 management console. For an example of how to launch an EC2 instance from the console, see Getting Started.

The script installs the NFS client and writes an entry in the /etc/fstab file that will identify the mount target DNS name as well as the subdirectory in your EC2 instance on which to mount the EFS file system. The script ensures the file gets mounted when the EC2 instance is launched and after each system reboot.

For more information about the customized version of cloud-init used by Amazon Linux, see cloud-init in the Amazon EC2 User Guide for Linux Instances.

To configure your EC2 instance to mount an EFS file system automatically at launch

  1. Open the Amazon EC2 console in your web browser, and begin the Launch Instance wizard.

  2. When you reach Step 3: Configure Instance Details, configure your instance details, expand the Advanced section, and then do the following:

    1. Paste the following script into User data. You must update the script by providing the appropriate values for file-system-id, aws-region, and efs-mount-point:

      #cloud-config package_upgrade: true packages: - nfs-utils runcmd: - mkdir -p /var/www/html/efs-mount-point/ - chown ec2-user:ec2-user /var/www/html/efs-mount-point/ - echo " /var/www/html/efs-mount-point nfs4 nfsvers=4.1,rsize=1048576,wsize=1048576,hard,timeo=600,retrans=2 0 0" >> /etc/fstab - mount -a -t nfs4

      If you are specifying a custom path to your mount point, as in the example, you may want to use mkdir -p, because the -p option creates intermediate parent directories as needed. The - chown line of the preceding example changes the ownership of the directory at the mount point from the root user to the default Linux system user account for Amazon Linux, ec2-user. You can specify any user with this command, or leave it out of the script to keep ownership of that directory with the root user.

      For more information about user data scripts, see Adding User Data in the Amazon EC2 User Guide for Linux Instances.

  3. Complete the Launch Instance wizard.


    To verify that your EC2 instance is working correctly, you can integrate these steps into the Getting Started exercise. For more information, see Getting Started.

Your EC2 instance is now configured to mount the EFS file system at launch.