我收到以下错误：
$ sudo apt-get update
# partial output
Reading package lists... Done
W: GPG error: https://download.01.org trusty Release:
The following signatures couldn't be verified because the public key is not available:
NO_PUBKEY A902DDA375E52366
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/InRelease
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/InRelease
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/InRelease
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease
W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/InRelease
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/Release.gpg Could not resolve 'us.archive.ubuntu.com'
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/Release.gpg Could not resolve 'us.archive.ubuntu.com'
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/Release.gpg Could not resolve 'us.archive.ubuntu.com'
W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/Release.gpg Could not resolve 'dl.google.com'
W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/Release.gpg Could not resolve 'extras.ubuntu.com'
W: Some index files failed to download. They have been ignored, or old ones used instead.
答案1
好的，经过多次尝试后我终于明白了：
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys A902DDA375E52366
然后我跑了
sudo apt-get update && sudo apt-get upgrade
但最终得到了和以前一样的错误：
The following packages have been kept back:
wine-staging wine-staging-amd64 wine-staging-i386:i386
0 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
然后我点击上面截图中显示的错误 -> 显示更新 -> 更新顺利完成。希望添加该键是正确的做法....？另外，有人知道我为什么开始收到此错误吗（这样我以后就可以避免这种情况）？