Debian9升级10：

apt-get update && apt-get upgrade

sed -i 's/stretch/buster/g' /etc/apt/sources.list

apt-get update && apt-get upgrade

apt-get dist-upgrade

reboot

apt-get autoremove

完成！

Debian10升级11：

apt update && apt -y upgrade && apt -y dist-upgrade; \
sed -i 's?buster/updates?bullseye-security?' /etc/apt/sources.list && sed -i 's/buster/bullseye/g' /etc/apt/sources.list; \
apt update && apt -y upgrade && apt -y dist-upgrade

reboot

apt-get autoremove

完成！