4. .yarnrc .yarnrc files allow you to configure additional Yarn features. The config command may also be used to set these options. Yarn will merge .yarnrc files up the file tree. 
yarn-offline-mirror  yarn-offline-mirror "./packages-cache" Maintain offline copies of your packages for more repeatable and reliable builds. Find more information here. Value must be a relative file path, or false to disable the mirror (default). 
yarn-offline-mirror-pruning  yarn-offline-mirror-pruning true Control automatic pruning of the offline mirror. Find more information here. Value must be a boolean, defaults to false. 
yarn-path  yarn-path "./bin/yarn" Instructs yarn to defer to another Yarn binary for execution. Useful if you want to bundle Yarn into your repository and have everyone use the same version for consistency. This was introduced in Yarn 1.0, so all developers must have Yarn >= 1.0 installed. Value must be a relative file path, or false to disable (default). 
disable-self-update-check  disable-self-update-check true When installing packages, Yarn will provide upgrade instructions if you have an outdated CLI installation. You can disable this check here. Value must be a boolean, defaults to false. 
child-concurrency  child-concurrency #number# Controls the number of child processes that run in parallel to build node modules. Setting this number to 1 will cause the node modules to be built sequentially which can avoid linker errors on windows with node-gyp. 
unsafe-disable-integrity-migration  unsafe-disable-integrity-migration false Setting this to false will enable the yarn.lock checksum migration (enabling sha512 support). Causes lockfile format change. This will be the default starting from version 2.0. CLI arguments  Setting --<command>.<flag> <value> in .yarnrc would be the same as running yarn <command> --<flag> <value>. Example: $> cat .yarnrc
--install.check-files true Is the same running yarn install --check-files Example 2: $> cat .yarnrc
--cache-folder /tmp/yarn-cache/

$> yarn cache dir
/tmp/yarn-cache/v1

    
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