##概要
macを買い替え、以前のPCで技術書を参考に自作したアプリケーションを立ち上げようとrails s をしたら、表題のエラーが出た。

##開発環境
MacBook Pro (13-inch, M1, 2020)
macOS Big Sur バージョン 11.5.2

##rails sでエラーが出た

terminal

$ rails s
~
An error occurred while installing pg (1.2.3), and Bundler cannot
continue.
Make sure that `gem install pg -v '1.2.3' --source 'https://rubygems.org/'`
succeeds before bundling.

素直にやってみる。

terminal

$ gem install pg -v '1.2.3'

terminal

$ rails s
Ignoring bootsnap-1.7.3 because its extensions are not built. Try: gem pristine bootsnap --version 1.7.3
Ignoring bootsnap-1.7.1 because its extensions are not built. Try: gem pristine bootsnap --version 1.7.1
Ignoring bootsnap-1.5.1 because its extensions are not built. Try: gem pristine bootsnap --version 1.5.1
Ignoring eventmachine-1.0.9.1 because its extensions are not built. Try: gem pristine eventmachine --version 1.0.9.1
Ignoring ffi-1.14.1 because its extensions are not built. Try: gem pristine ffi --version 1.14.1
Ignoring ffi-1.13.1 because its extensions are not built. Try: gem pristine ffi --version 1.13.1
Ignoring ffi-1.12.2 because its extensions are not built. Try: gem pristine ffi --version 1.12.2
Ignoring msgpack-1.3.3 because its extensions are not built. Try: gem pristine msgpack --version 1.3.3
Ignoring nio4r-2.5.5 because its extensions are not built. Try: gem pristine nio4r --version 2.5.5
Ignoring nio4r-2.5.4 because its extensions are not built. Try: gem pristine nio4r --version 2.5.4
Ignoring sqlite3-1.4.0 because its extensions are not built. Try: gem pristine sqlite3 --version 1.4.0
Ignoring thin-1.8.0 because its extensions are not built. Try: gem pristine thin --version 1.8.0
Ignoring thin-1.5.1 because its extensions are not built. Try: gem pristine thin --version 1.5.1
=> Booting Puma
=> Rails 5.2.4.5 application starting in development 
=> Run `rails server -h` for more startup options
Puma starting in single mode...
* Version 3.12.6 (ruby 2.6.6-p146), codename: Llamas in Pajamas
* Min threads: 5, max threads: 5
* Environment: development
* Listening on tcp://localhost:3000
Use Ctrl-C to stop

一応サーバーは立ち上がったが、Ignoringが気になるので消したい。

$　gem install bundler

$　bundle install

で消えました。

##参考
https://tsubasa0105.hatenablog.com/entry/2018/11/29/180051
https://qiita.com/ROY_M/items/43fd1370e3d89ae50074
https://teratail.com/questions/139925