EC2 unicornが起動できない、unicorn.logが生成されない

abstract
- unicornが起動できない
- エラーログを確認しようと思ったがunicorn.logが生成されていない
- 別件だがNginxのログファイルも生成されていない(こちらはログファイルの記述自体を削除したのでエラーは吐かれていない)

こちらの記事を参考にrailsアプリをデプロイしようとしています。
https://qiita.com/naoki_mochizuki/items/5a1757d222806cbe0cd1

sudo service nginx startコマンドでNginxを起動した後に下記の画面が表示されたので
Nginx起動後

bash
[username@ip]$ unicorn_rails -c /var/www/rails/rails_app/config/unicorn.conf.rb -D -E production
Traceback (most recent call last):
	11: from /home/username/.rbenv/versions/2.5.1/bin/unicorn_rails:23:in `<main>'
	10: from /home/username/.rbenv/versions/2.5.1/bin/unicorn_rails:23:in `load'
	 9: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/bin/unicorn_rails:209:in `<top (required)>'
	 8: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/bin/unicorn_rails:209:in `new'
	 7: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/lib/unicorn/http_server.rb:79:in `initialize'
	 6: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/lib/unicorn/http_server.rb:79:in `new'
	 5: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/lib/unicorn/configurator.rb:77:in `initialize'
	 4: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/lib/unicorn/configurator.rb:84:in `reload'
	 3: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/lib/unicorn/configurator.rb:84:in `instance_eval'
	 2: from /var/www/rails/rails_app/config/unicorn.conf.rb:10:in `reload'
	 1: from /home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/lib/unicorn/configurator.rb:607:in `working_directory'
/home/username/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/unicorn-5.5.1/lib/unicorn/configurator.rb:607:in `chdir': No such file or directory @ dir_s_chdir - /var/www/rails/rails_app (Errno::ENOENT)
master failed to start, check stderr log for details

unicornのエラーログを確認しようとしたところアプリケーション配下のlogディレクトリにunicorn.logが存在していませんでした。

bash
[username@ip log]$ ls
production.log

[username@ip rails_app]$ less log/unicorn.stderr.log 
log/unicorn.stderr.log: No such file or directory

ログの確認方法 or ログファイルが生成されていない原因を教えていただけると幸いです。

プロセスの確認↓

[username@ip rails_app]$ ps -ef | grep unicorn
username    30290 29889  0 06:36 pts/0    00:00:00 grep --color=auto unicorn

[username@ip rails_app]$ ps -ef | grep unicorn | grep -v grep
//出力なし

unicorn.conf.rb

unicorn.conf.rb
# set lets
  $worker  = 2
  $timeout = 30
  $app_dir = "/var/www/rails/rails_app" #
  $listen  = File.expand_path 'tmp/sockets/.unicorn.sock', $app_dir
  $pid     = File.expand_path 'tmp/pids/unicorn.pid', $app_dir
  $std_log = File.expand_path 'log/unicorn.log', $app_dir
  # set config
  worker_processes  $worker
  working_directory $app_dir
  stderr_path $std_log
  stdout_path $std_log
  timeout $timeout
  listen  $listen
  pid $pid
  # loading booster
  preload_app true
  # before starting processes
  before_fork do |server, worker|
    defined?(ActiveRecord::Base) and ActiveRecord::Base.connection.disconnect!
    old_pid = "#{server.config[:pid]}.oldbin"
    if old_pid != server.pid
      begin
        Process.kill "QUIT", File.read(old_pid).to_i
      rescue Errno::ENOENT, Errno::ESRCH
      end
    end
  end
  # after finishing processes
  after_fork do |server, worker|
    defined?(ActiveRecord::Base) and ActiveRecord::Base.establish_connection
  end