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rhelのドキュメントよめ

https://access.redhat.com/documentation/ja-jp/red_hat_enterprise_linux/8/html/configuring_basic_system_settings/automatically-refreshing-package-database_installing-software-with-yum#how-dnf-automatic-operates_automatically-refreshing-package-database
https://access.redhat.com/documentation/ja-jp/red_hat_enterprise_linux/8/html/considerations_in_adopting_rhel_8/removed_security_functionality