Кто-либо знает, где найти хороший источник репозиториев обновления Linux?

Каждый раз, когда я пытаюсь обновить склонное использование - получают обновление, моя виртуальная машина Ubuntu 16.04 сталкивается с этими ошибками

W: The repository 'http://security.ubuntu.com/ubuntu xenial-security Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://us.archive.ubuntu.com/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://us.archive.ubuntu.com/ubuntu xenial-updates Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://us.archive.ubuntu.com/ubuntu xenial-backports Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/main/binary-amd64/Packages  403  Forbidden [IP: 91.189.91.24 80]
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial/main/binary-amd64/Packages  403  Forbidden [IP: 91.189.91.14 80]
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-amd64/Packages  403  Forbidden [IP: 91.189.91.14 80]
E: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/xenial-backports/main/binary-amd64/Packages  403  Forbidden [IP: 91.189.91.14 80]

Я использую новую установку Ubuntu 16.04 для практики для конкуренции, и я сталкиваюсь с той же ошибкой на конкуренции.