由于某种原因无法启动Puma。收到此错误
ArgumentError: couldn't find login name -- expanding `~'
带有下面的回溯图
Feb 03 15:44:21 shopify-shipping-refactor puma[3061]: Done in 1.33s.
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: rake aborted!
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: ArgumentError: couldn't find login name -- expanding `~'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/pry-0.12.2/lib/pry/pry_class.rb:5:in `expand_path'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/pry-0.12.2/lib/pry/pry_class.rb:5:in `<class:Pry>'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/pry-0.12.2/lib/pry/pry_class.rb:1:in `<top (required)>'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/pry-0.12.2/lib/pry.rb:119:in `require'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/pry-0.12.2/lib/pry.rb:119:in `<top (required)>'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in `require'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in `block (2 levels) in require'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in `each'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in `block in require'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in `each'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in `require'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/bundler-2.1.4/lib/bundler.rb:174:in `require'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /opt/shopify_shipping_refactor/config/application.rb:7:in `<top (required)>'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /opt/shopify_shipping_refactor/Rakefile:4:in `require'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /opt/shopify_shipping_refactor/Rakefile:4:in `<top (required)>'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/gems/rake-13.0.1/exe/rake:27:in `<top (required)>'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/bin/ruby_executable_hooks:24:in `eval'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: /usr/local/rvm/gems/ruby-2.6.5/bin/ruby_executable_hooks:24:in `<main>'
Feb 03 15:44:25 shopify-shipping-refactor puma[3061]: (See full trace by running task with --trace)
Feb 03 15:44:25 shopify-shipping-refactor systemd[1]: puma.service: Control process exited, code=exited status=1
Feb 03 15:44:25 shopify-shipping-refactor systemd[1]: Failed to start puma.service.
Feb 03 15:44:25 shopify-shipping-refactor systemd[1]: puma.service: Unit entered failed state.
Feb 03 15:44:25 shopify-shipping-refactor systemd[1]: puma.service: Failed with result 'exit-code'.
Analysis： Ruby的expand_path调用基于C的运行时（模糊了堆栈跟踪），但最终以rb_default_home_dir结尾找出rb_default_home_dir是什么。此方法依靠'~'环境变量来解决，并退回到$HOME（getlogin()）和getlogin(3)（如果不可用）。
原因：您看到的错误消息来自该后备失败，因为（大概）您的进程未向控制tty和登录用户注册。
解决方案：运行puma时设置$ HOME。当指定getpwnam()时，使用您希望Puma用作主目录的目录。