一、首先需要从16.04 → 18.04
sudo mv /etc/apt/sources.list ~/
sudo mv /etc/apt/sources.list.d/*.list ~/
1. 改变源（粘贴下面这一段到终端并运行）
cat <<EOF | sudo tee /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu/ xenial-backports main universe multiverse restricted
deb http://archive.ubuntu.com/ubuntu/ xenial main universe multiverse restricted
deb http://archive.ubuntu.com/ubuntu/ xenial-updates main universe multiverse restricted
deb http://security.ubuntu.com/ubuntu/ xenial-security main universe multiverse restricted
EOF
2. 依次执行以下语句
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ xenial-backports main universe multiverse restricted"
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ xenial main universe multiverse restricted"
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ xenial-updates main universe multiverse restricted"
sudo add-apt-repository "deb http://security.ubuntu.com/ubuntu/ xenial-security main universe multiverse restricted"
3. 执行升级
sudo apt-get update
sudo apt-get upgrade
sudo apt-get purge ubuntu-advantage-tools --autoremove
sudo rm /etc/apt/sources.list.d/ubuntu-esm-infra.list
sudo do-release-upgrade
二、18.04 → 20.04
基本一样的步骤,但是必须要先升级到18.04：
sudo mv /etc/apt/sources.list ~/
sudo mv /etc/apt/sources.list.d/*.list ~/
1. 改变源（粘贴下面这一段到终端并运行）
cat <<EOF | sudo tee /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu/ bionic-backports main universe multiverse restricted
deb http://archive.ubuntu.com/ubuntu/ bionic main universe multiverse restricted
deb http://archive.ubuntu.com/ubuntu/ bionic-updates main universe multiverse restricted
deb http://security.ubuntu.com/ubuntu/ bionic-security main universe multiverse restricted
EOF
2. 依次执行以下语句
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ bionic-backports main universe multiverse restricted"
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ bionic main universe multiverse restricted"
sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu/ bionic-updates main universe multiverse restricted"
sudo add-apt-repository "deb http://security.ubuntu.com/ubuntu/ bionic-security main universe multiverse restricted"
3. 执行升级
sudo apt-get update
sudo apt-get upgrade
sudo apt-get purge ubuntu-advantage-tools --autoremove
sudo rm /etc/apt/sources.list.d/ubuntu-esm-infra.list
sudo do-release-upgrade
Q&A
1. sudo apt-get update 报错
E: 无法下载 http://security.ubuntu.com/ubuntu/dists/xenial-security/universe/dep11/Components-amd64.yml 无法打开文件 /var/lib/apt/lists/partial/security.ubuntu.com_ubuntu_dists_xenial-security_universe_dep11_Components-amd64.yml.xz - open (13: 权限不够) [IP: 185.125.190.39 80]
E: 部分索引文件下载失败。如果忽略它们，那将转而使用旧的索引文件。
解决：到这个目录下删掉这个就行；（我是备份了一下，以防有用）
2. ModuleNotFoundError: No module named ‘softwareproperties’
解决：依次执行以下操作：
sudo vi /usr/bin/add-apt-repository
#!/usr/bin/python3修改为#!/usr/bin/python3.5即可。
3. ModuleNotFoundError: No module named ‘lsb_release’
解决：依次执行以下操作：
sudo vi /usr/bin/lsb_release
更改：#!/usr/bin/python3.5m -Es
4. ModuleNotFoundError: No module named ‘DistUpgrade’
解决：依次执行以下命令：
head -n1 /usr/bin/do-release-upgrade #找到指向的python
sudo rm -rf /usr/bin/python3 # 上面找到的python链接
ln -s /usr/bin/python3.5 /usr/bin/python3 # 用原始链接替换
目前遇到的问题就这些，欢迎在评论区补充~
