为了使用qt6，在ubuntu18.04上各种折腾失败，无奈只能升级到ubuntu20.04, 按照网上的教程没成功。自己摸索了

lsb_release -a
df -h
sudo apt update
sudo apt upgrade -y
sudo apt dist-upgrade -y
sudo apt autoremove -y
sudo apt clean
sudo apt install update-manager-core
vi sudo nano /etc/update-manager/release-upgrades
sudo vi /etc/update-manager/release-upgrades
sudo do-release-upgrade
sudo do-release-upgrade -m desktop -d
sudo apt install --reinstall update-manager-core
sudo apt install --reinstall python3
sudo apt install --reinstall python3-distupgrade
grep Prompt /etc/update-manager/release-upgrades
sudo apt-mark showhold
sudo apt dist-upgrade
sudo do-release-upgrade -m desktop -d
sudo apt update
sudo apt upgrade
sudo apt full-upgrade
sudo apt autoremove
sudo systemctl reboot
sudo update-manager
cd /usr/bin
ls -l | grep python
sudo do-release-upgrade -d -f DistUpgradeViewGtk3
sudo apt-get install ubuntu-release-upgrader-core
sudo vi /etc/apt/sources.list
sudo apt update
sudo apt dist-upgrade -y
sudo dpkg --configure -a
dpkg -l | grep -E '^iF'
sudo apt-get install --reinstall apparmor udev
sudo apt --fix-broken install
lsb_release
lsb_release --version
lsb --version
ls -ld /etc/apparmor.d/cache/e10c1cf9.0
sudo rm -rf /etc/apparmor.d/cache/e10c1cf9.0
sudo rm -rf /etc/apparmor.d/cache/*
sudo apt-get install --reinstall apparmor
sudo apt --fix-broken install
sudo apt-get update && sudo apt-get upgrade
ls /usr/lib/x86_64-linux-gnu/libapt-pkg.so.5.0
sudo apt-get download libapt-pkg5.0
sudo dpkg -i libapt-pkg5.0_*.deb
apt-cache policy libapt-pkg5.0
sudo vi /etc/apt/sources.list
sudo apt-get update
ls /var/cache/apt/archives/ -l
cd ~
wget https://security.ubuntu.com/ubuntu/pool/main/a/apt/libapt-pkg5.0_1.6.17_amd64.deb
dpkg -i libapt-pkg5.0_1.6.17_amd64.deb
sudo dpkg -i libapt-pkg5.0_1.6.17_amd64.deb
wget https://security.ubuntu.com/ubuntu/pool/main/a/apt/libapt-pkg5.0_1.6.17_amd64.deb
sudo dpkg -i libapt-pkg5.0_1.6.17_amd64.deb
wget https://launchpad.net/ubuntu/focal/amd64/libapt-pkg6.0/2.0.2
ls
sudo apt-get update
sudo apt-get upgrade
sudo apt --fix-broken install
lsb_release -a
sudo apt dist-upgrade -y
lsb_release -a

关键的一步，要修改sudo vi /etc/apt/sources.list 将其中的源替换成ubuntu20.04

即将将 bionic 替换为 focal.

具体为：

1、编辑 sources.list 文件

1）使用 vi 打开 sources.list 文件：

sudo vi /etc/apt/sources.list

2）

1. 查找和替换： 将 bionic 替换为 focal。在 vi 中，您可以使用以下命令：

   • 进入命令模式（按下 ESC）。
   • 输入以下命令替换所有出现的 bionic 为 focal：

     :%s/bionic/focal/g

2. 保存并退出：

   • 按下 ESC 键。
   • 输入以下命令保存并退出

---

更新系统并升级

完成源替换后，更新并升级系统：

sudo apt update sudo apt dist-upgrade -y