我正在使用 ubuntu 18.04，当我尝试该apt-get update命令时，我得到：
Hit:1 https://repo.skype.com/deb stable InRelease
Hit:2 http://ppa.launchpad.net/jonathonf/mate-1.22/ubuntu bionic InRelease
Get:3 http://security.ubuntu.com/ubuntu bionic-security InRelease [88,7 kB]
Get:4 http://linux.dropbox.com/ubuntu bionic InRelease
Err:4 http://linux.dropbox.com/ubuntu bionic InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:5 http://dl.google.com/linux/chrome/deb stable InRelease
Err:5 http://dl.google.com/linux/chrome/deb stable InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:6 http://es.archive.ubuntu.com/ubuntu bionic InRelease
Err:6 http://es.archive.ubuntu.com/ubuntu bionic InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Ign:7 http://ppa.launchpad.net/ubuntu-mate-dev/ppa/ubuntu bionic InRelease
Get:8 http://es.archive.ubuntu.com/ubuntu bionic-updates InRelease
Err:8 http://es.archive.ubuntu.com/ubuntu bionic-updates InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:9 http://es.archive.ubuntu.com/ubuntu bionic-backports InRelease
Err:9 http://es.archive.ubuntu.com/ubuntu bionic-backports InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Ign:10 http://ppa.launchpad.net/ubuntu-mate-dev/trusty-mate/ubuntu bionic InRelease
Err:11 http://ppa.launchpad.net/ubuntu-mate-dev/ppa/ubuntu bionic Release
404 Not Found [IP: 91.189.95.83 80]
Err:12 http://ppa.launchpad.net/ubuntu-mate-dev/trusty-mate/ubuntu bionic Release
404 Not Found [IP: 91.189.95.83 80]
Reading package lists... Done
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://linux.dropbox.com/ubuntu bionic InRelease' is not signed.
E: Failed to fetch http://linux.dropbox.com/ubuntu/dists/bionic/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://dl.google.com/linux/chrome/deb stable InRelease' is not signed.
E: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
N: See apt-secure(8) manpage for repository creation and user configuration details.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
E: The repository 'http://es.archive.ubuntu.com/ubuntu bionic InRelease' is not signed.
E: Failed to fetch http://es.archive.ubuntu.com/ubuntu/dists/bionic/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch http://es.archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://es.archive.ubuntu.com/ubuntu bionic-updates 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.
E: Failed to fetch http://es.archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://es.archive.ubuntu.com/ubuntu bionic-backports 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.
E: The repository 'http://ppa.launchpad.net/ubuntu-mate-dev/ppa/ubuntu bionic Release' does not have a Release file.
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.
E: The repository 'http://ppa.launchpad.net/ubuntu-mate-dev/trusty-mate/ubuntu bionic Release' does not have a Release file.
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.
我不知道发生了什么。出了什么问题？
编辑：有一个类似的问题，但问题出在 OP 大学的连接上。我在不同的设置中都遇到了这个错误，所以我不认为这是问题所在
答案1
可能有点晚了，但我会简单写下我遇到类似问题时所做的事情，希望对以后的某人有用：
Get:10 http://ny-mirrors.evowise.com/ubuntu focal-security InRelease [611 kB]
Err:6 http://ny-mirrors.evowise.com/ubuntu focal InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Err:7 http://ny-mirrors.evowise.com/ubuntu focal-updates InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Err:9 http://ny-mirrors.evowise.com/ubuntu focal-backports InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Err:10 http://ny-mirrors.evowise.com/ubuntu focal-security InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
为了解决这个问题，在我的 Kubuntu 中，我简单地更改了 apt 将从中获取更新的 ubuntu 存储库服务器：
我只是选择了与 apt 之前配置的获取服务器不同的服务器。之后，apt 能够毫无问题地获取更新。