我已经完成了Ubuntu 16.04的全新安装。安装系统后,我已经为我安装了其他一些必要的应用程序(包括Opera浏览器,Intel图形驱动程序等)。现在,当我尝试使用从终端更新系统时sudo apt-get update
。它给我以下错误
W: The repository 'https://deb.opera.com/opera-stable stable 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: GPG error: https://download.01.org/gfx/ubuntu/16.04/main xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 56A3DEF863961D39
W: The repository 'https://download.01.org/gfx/ubuntu/16.04/main xenial 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.
E: Failed to fetch https://deb.opera.com/opera-stable/dists/stable/non-free/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
我该如何克服这个问题?