更新：
webup8 存在问题，但更大的问题是它存在不一致的 DNS 问题，如果我刷新，浏览器也无法找到网站，并且会像平常一样加载。
当执行 apt 时，它会在启动前停留 30 秒，处于 [Working]0% 状态。
有任何想法吗？
在 iMac 上全新安装 17.10
浏览器可以通过 wifi 正常使用，但是无法通过 apt-get 进行更新，已经尝试了两天了。
尝试过不同的镜像，问题依旧
第一次给出的理由不一致
$ sudo apt-get update
[sudo] password for andrew:
Ign:1 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:2 http://archive.ubuntu.com/ubuntu artful InRelease
Hit:3 http://archive.ubuntu.com/ubuntu artful-updates InRelease
Hit:4 http://dl.google.com/linux/chrome/deb stable Release
Hit:6 http://archive.ubuntu.com/ubuntu artful-backports InRelease
Hit:7 http://archive.ubuntu.com/ubuntu artful-security InRelease
Err:8 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease
Could not resolve 'ppa.launchpad.net'
Hit:9 http://archive.canonical.com/ubuntu artful InRelease
Reading package lists... Done
W: Failed to fetch http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu/dists/artful/InRelease Could not resolve 'ppa.launchpad.net'
W: Some index files failed to download. They have been ignored, or old ones used instead.
这是第二个：
$ sudo apt-get update
Ign:1 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:2 http://archive.canonical.com/ubuntu artful InRelease
Hit:3 http://dl.google.com/linux/chrome/deb stable Release
Hit:5 http://archive.ubuntu.com/ubuntu artful InRelease
Get:6 http://archive.ubuntu.com/ubuntu artful-updates InRelease [81.7 kB]
Get:7 http://archive.ubuntu.com/ubuntu artful-backports InRelease [72.2 kB]
Get:8 http://archive.ubuntu.com/ubuntu artful-security InRelease [78.6 kB]
Get:9 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease [15.4 kB]
Err:9 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 531EE72F4C9D234C
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 531EE72F4C9D234C
E: The repository 'http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease' is not signed.
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.
这是第三个：
$ sudo apt-get update
Ign:1 http://dl.google.com/linux/chrome/deb stable InRelease
Hit:3 http://archive.ubuntu.com/ubuntu artful InRelease
Hit:4 http://dl.google.com/linux/chrome/deb stable Release
Get:2 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease [15.4 kB]
Err:2 http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 531EE72F4C9D234C
Get:6 http://archive.ubuntu.com/ubuntu artful-updates InRelease [81.7 kB]
Get:7 http://archive.ubuntu.com/ubuntu artful-backports InRelease [72.2 kB]
Get:8 http://archive.ubuntu.com/ubuntu artful-security InRelease [78.6 kB]
Hit:9 http://archive.canonical.com/ubuntu artful InRelease
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 531EE72F4C9D234C
E: The repository 'http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu artful InRelease' is not signed.
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.
唯一不变的是它永远不会成功:(
以下是我的资料来源：
在此先感谢您的帮助
答案1
webupd8 自 2017 年底以来一直处于停用状态，因此大多数或所有存储库都处于停用状态，可能会导致您遇到的问题