In order to update welcome message after ssh a.k.a message of the day (motd) we need to write our custom motd script to the AWS ElasticBeanstalk (EB) EC2 instace /etc/update-motd.d/20-custom-welcome-message

in order to do that we can tell .ebextensions to write that file after deployment

If you need more info on what the f. in .ebextensions check this article

Inside your project folder (where you execute eb deploy or eb ssh) create folder .ebextensions and crate a file .ebextensions/91_update_motd_welcome_message_after_ssh.config with content

files:
  "/tmp/20-custom-welcome-message":
    mode: "000755"
    owner: root
    group: root
    content: |
      cat << EOF
      THIS WILL BE YOUR WELCOME MESSAGE
      EOF

commands:
  80_tell_instance_to_regenerate_motd:
    command: mv /tmp/20-custom-welcome-message /etc/update-motd.d/20-custom-welcome-message

  99_tell_instance_to_regenerate_motd:
    command: /usr/sbin/update-motd

We create motd file to /tmp/ folder and then copy it to /etc/update-motd.d where it’s picked up. Reason why we don’t write it directly to this folder is because .ebextensions files will create .bck file with a backup of the original file on server. This would result in two motd messages.

Force motd regenerate

we are running following to regenerate motd files so that it’s picked up by instance without restart

sudo /usr/sbin/update-motd

if this don’t work try

sudo run-parts /etc/update-motd.d/

Based on this article

my custom welcome message

If interested here is my setup is Ruby on Rails application running in Docker container. I like to output quick copy-paste docker exec commands for ease of use. The image name is my-webserver-v3 or my-webserver-v3 that’s why the grep v3 part

files:
  "/tmp/20-custom-welcome-message":
    mode: "000755"
    owner: root
    group: root
    content: |
      cat << EOF

      This EC2 instance is running Docker container with Ruby on Rails. To access the container:

          sudo docker ps
          sudo docker exec -it xxxxxxx bash
          sudo docker exec -it \$( sudo docker ps | grep v3 | awk '{print \$1;}' | tail -n 1) bash

      To execute Ruby on Rails console:

          sudo docker ps
          sudo docker exec -it xxxxxxx bin/rails c
          sudo docker exec -it \$( sudo docker ps | grep v3 | awk '{print \$1;}' | tail -n 1) bin/rails c

      EOF

commands:
  80_tell_instance_to_regenerate_motd:
    command: mv /tmp/20-custom-welcome-message /etc/update-motd.d/20-custom-welcome-message

  99_tell_instance_to_regenerate_motd:
    command: /usr/sbin/update-motd

related & sources