How do I mount an Amazon EFS volume to an application directory in an Elastic Beanstalk environment?

Short description

The following resolution provides general instructions to mount an Amazon EFS volume on platforms based on Amazon Linux 1. The resolution uses the PHP solution stack.
If you use a different solution stack, then choose the correct application directory and staging directory for your solution stack from the following options:

-----------------------------------------------------
Solution stack             Application directory                    Staging directory
Nodejs                     /var/app/current                         /tmp/deployment/application
PHP                        /var/app/current                         /var/app/ondeck
Ruby (Passenger)           /var/app/current                         /var/app/ondeck
Ruby (Puma)                /var/app/current                         /var/app/ondeck
Java with Tomcat           /usr/share/tomcat*/webapps/ROOT          /tmp/deployment/application/ROOT
Java SE                    /var/app/current                         /var/app/staging
Python                     /opt/python/current/app                  /opt/python/ondeck/app
Go                         /var/app/current                         /var/app/staging
Single Container Docker    /var/app/current                         /var/app/staging
Multi-Container Docker     /var/app/current                         /var/app/staging
-----------------------------------------------------

Important: When you deploy an Elastic Beanstalk application, the contents of /var/app/current are moved to /var/app/current.old. You can't directly mount an Amazon EFS volume to the application directory. The current deployed source bundle is moved to the application directory. If you mount the Amazon EFS volume to /var/app/current, then that volume is moved to /var/app/current.old after the deployment is completed.

Example eb-activity.log output:

===============================
[2020-02-12T02:28:18.237Z] INFO  [3159]  - [Application deployment Sample Application@1/StartupStage1/AppDeployEnactHook/01_flip.sh] : Starting activity...
[2020-02-12T02:28:18.431Z] INFO  [3159]  - [Application deployment Sample Application@1/StartupStage1/AppDeployEnactHook/01_flip.sh] : Completed activity. Result:
  ++ /opt/elasticbeanstalk/bin/get-config container -k app_staging_dir
  + EB_APP_STAGING_DIR=/var/app/ondeck
  ++ /opt/elasticbeanstalk/bin/get-config container -k app_deploy_dir
  + EB_APP_DEPLOY_DIR=/var/app/current
  + '[' -d /var/app/current ']'
  + mv /var/app/current /var/app/current.old
  + mv /var/app/ondeck /var/app/current
  + nohup rm -rf /var/app/current.old
===============================

Resolution

To mount an Amazon EFS volume to an application directory in an Elastic Beanstalk environment, complete the following steps:

1. Confirm that your source bundle is unzipped in the staging directory. For more information, see Viewing logs from Amazon Elastic Compute Cloud (Amazon EC2) instances in your Elastic Beanstalk environment.
   Example eb-activity.log output:

   ===============================
   [2020-02-12T02:28:16.336Z] INFO  [3159]  - [Application deployment Sample Application@1/StartupStage0/AppDeployPreHook/01_unzip.sh] : Starting activity...
   [2020-02-12T02:28:16.631Z] INFO  [3159]  - [Application deployment Sample Application@1/StartupStage0/AppDeployPreHook/01_unzip.sh] : Completed activity. Result:
     ++ /opt/elasticbeanstalk/bin/get-config container -k app_user
     + EB_APP_USER=webapp
     ++ /opt/elasticbeanstalk/bin/get-config container -k app_staging_dir
     + EB_APP_STAGING_DIR=/var/app/ondeck
     ++ /opt/elasticbeanstalk/bin/get-config container -k source_bundle
     + EB_SOURCE_BUNDLE=/opt/elasticbeanstalk/deploy/appsource/source_bundle
     + rm -rf /var/app/ondeck
     + /usr/bin/unzip -d /var/app/ondeck /opt/elasticbeanstalk/deploy/appsource/source_bundle
     Archive:  /opt/elasticbeanstalk/deploy/appsource/source_bundle
        creating: /var/app/ondeck/.ebextensions/
       inflating: /var/app/ondeck/.ebextensions/logging.config
        inflating: /var/app/ondeck/scheduled.php
        inflating: /var/app/ondeck/index.php
        inflating: /var/app/ondeck/cron.yaml
        inflating: /var/app/ondeck/styles.css
       extracting: /var/app/ondeck/logo_aws_reduced.gif
      + chown -R webapp:webapp /var/app/ondeck
     + chmod 775 /var/app/ondeck
   ===============================

   Note: All the appdeploy pre hooks in /opt/elasticbeanstalk/hooks/appdeploy/pre/ and .ebextensions are run in the staging directory.
2. Create an .ebextensions folder in the root directory of the source bundle.
3. To mount an Amazon EFS volume to a specific directory, such as /efs, add a formatted configuration file (YAML or JSON) to your directory.
4. To mount your Amazon EFS volume to an application directory, create a symlink to the staging directory. To create a symlink from /efs that points to the staging directory, use container_commands to create a .config file in your .ebextensions folder.
   Example:

   container_commands:
     01_symlink:
       command: ln -s /efs /var/app/ondeck/

   Note: When appdeploy enact hooks are run during a deployment in an Elastic Beanstalk environment, the staging directory contents are moved to the application directory. For example, in a PHP solution, the flip.sh script moves the contents of the staging directory to the application directory. The flip.sh script is the first script of AppDeployEnactHook in /opt/elasticbeanstalk/hooks/appdeploy/enact/.