我使用 ubuntu
描述：Ubuntu 20.04.3 LTS
发行：20.04
代号：focal
我尝试了 sudo apt update，以前没有问题，但最近出现如下错误
Ign:2 http://my.archive.ubuntu.com/ubuntu focal-updates InRelease
Ign:3 http://my.archive.ubuntu.com/ubuntu focal-backports InRelease
Ign:4 http://my.archive.ubuntu.com/ubuntu focal-security InRelease
Err:5 http://my.archive.ubuntu.com/ubuntu focal Release
404 Not Found [IP: 202.79.184.254 80]
Err:6 http://my.archive.ubuntu.com/ubuntu focal-updates Release
404 Not Found [IP: 202.79.184.254 80]
Err:7 http://my.archive.ubuntu.com/ubuntu focal-backports Release
404 Not Found [IP: 202.79.184.254 80]
Err:8 http://my.archive.ubuntu.com/ubuntu focal-security Release
404 Not Found [IP: 202.79.184.254 80]
Reading package lists... Done
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal-updates Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal-backports Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://my.archive.ubuntu.com/ubuntu focal-security Release' no longer has a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
我检查了http://my.archive.ubuntu.com/ubuntu，未找到网址。
对此有什么想法吗？我是 Linux 新手。
谢谢