На этот вопрос уже есть ответ здесь:
Я получаю эту ошибку, когда пытаюсь обновить свой Ubuntu 17.04. Я уже пробовал несколько решений, но пока ничего не работает. Я получаю следующие ошибки:
Reading package lists... Done
W: GPG error: http://archive.canonical.com/ubuntu precise Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5
W: The repository 'http://archive.canonical.com/ubuntu precise Release' is not signed.
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: GPG error: http://extras.ubuntu.com/ubuntu precise Release: The following signatures were invalid: C47415DFF48C09645B78609416126D3A3E5C1192
W: The repository 'http://extras.ubuntu.com/ubuntu precise Release' is not signed.
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: GPG error: http://us.archive.ubuntu.com/ubuntu precise-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5
W: The repository 'http://us.archive.ubuntu.com/ubuntu precise-security InRelease' is not signed.
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: GPG error: http://us.archive.ubuntu.com/ubuntu precise-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5
W: The repository 'http://us.archive.ubuntu.com/ubuntu precise-updates InRelease' is not signed.
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: GPG error: http://us.archive.ubuntu.com/ubuntu precise-backports InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5
W: The repository 'http://us.archive.ubuntu.com/ubuntu precise-backports InRelease' is not signed.
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.
выполните эту команду к baukup Ваш sourses.list..
sudo mv /etc/apt/sources.list /etc/apt/sources.list.bak
затем переходят к этой странице Исходный Генератор Списка Ubuntu
затем погрузка, Ваша страна и Ваш выпуск человечности затем Генерируют listafter, которые копируют и мимо него, после того, как выполнено эта команда sudo nano /etc/apt/sources.list
последняя команда sudo apt-get update
Развлекайтесь!