Have problem with appspec.yml for deploy ruby on rails to ec2 instance with AWS CodeDeploy and AWS CodePipeline.

Hi I new on AWS here. I want to try to deploy some ruby on rails project to ec2 instance and my use case I want is when I deploy code to GitHub to my specific branch (like branch master etc.) I want it to deploy to my ec2 instance right after push to that branch. and I run into this guide (link) they use AWS CodeDeploy and AWS CodePipeline in this guide. I try to following they step and I got struck at appspec.yml. I try to following appspec.yml in this guide and make some modify to following code.

appspec.yml

version: 0.0
os: linux
files:
- source: /
destination: /var/www/eb-rails/deployment
file_exists_behavior: OVERWRITE
permissions:
- object: /var/www/eb-rails/deployment
pattern: "**"
owner: ubuntu
group: ubuntu
mode: 775
hooks:
AfterInstall:
- location: scripts/dependencies_install.sh
runas: ubuntu

and my scripts/dependencies_install.sh

#!/bin/bash
export PATH=/home/ubuntu/.rvm/gems/ruby-2.7.8/bin:/home/ubuntu/.rvm/gems/ruby-2.7.8@global/bin:/home/ubuntu/.rvm/rubies/ruby-2.7.8/bin:/home/ubuntu/bin:/home/ubuntu/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/ubuntu/.rvm/bin:/home/ubuntu/.rvm/bin
sudo kill -9 $(cat /var/www/my-app/tmp/pids/server.pid)
cd /var/www/my-app/
#sudo apt-get install ruby2.3-dev libffi-dev -y
gem install nokogiri — — use-system-libraries
bundle config build.nokogiri — use-system-libraries
gem install bundler — user-install
bundle install

note my ruby-version in this test project is 2.7.8

so I following guide and when I push code to my github it trigger my both AWS CodeDeploy and AWS CodePipeline but the deploy failed and when I try to see in log in my ec2 instance with less /var/log/aws/codedeploy-agent/codedeploy-agent.log I found this

2023-07-25T03:07:12 INFO  [codedeploy-agent(713)]: [Aws::CodeDeployCommand::Client 200 0.020335 0 retries] put_host_command_complete(command_status:"Failed",diagnostics:{format:"JSON",payload:"{\"error_code\":5,\"script_name\":\"\",\"message\":\"The deployment failed because the application specification file specifies only a source file (/). Add the name of the destination file to the files section of the AppSpec file, and then try again.\",\"log\":\"\"}"},host_command_identifier:"some base64 word here.......")

so I want to know where I gone wrong in my appspec.yml? I try to look into another guide they can set source: / normally but I get this in log.