fedora大版本升级记录
dnf update --refresh -y
dnf install dnf-plugin-system-upgrade -y
dnf system-upgrade download --releasever=$((`awk '{ print $3 }' /etc/fedora-release` + 1 )) --allowerasing -y
dnf system-upgrade reboot -y
dnf --releasever $((`awk '{ print $3 }' /etc/fedora-release` + 1 )) upgrade -y一路从23逐步升级到31
