我对 OwnCloud 桌面版本的更新有疑问：
teddy@Yoga-2:~$ sudo apt-get update --allow-unauthenticated
[sudo] password for teddy:
Hit:1 http://archive.ubuntu.com/ubuntu xenial InRelease
Ign:2 http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Ubuntu_15.10 InRelease
Get:3 http://archive.ubuntu.com/ubuntu xenial-updates InRelease [94,5 kB]
Get:4 http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Ubuntu_15.10 Release [1023 B]
Get:5 http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Ubuntu_15.10 Release.gpg [189 B]
Ign:5 http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Ubuntu_15.10 Release.gpg
Hit:6 http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Ubuntu_15.10 Packages
Hit:7 http://archive.ubuntu.com/ubuntu xenial-backports InRelease
Get:8 http://archive.ubuntu.com/ubuntu xenial-security InRelease [94,5 kB]
Get:9 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [242 kB]
Get:10 http://archive.ubuntu.com/ubuntu xenial-updates/main i386 Packages [238 kB]
Get:11 http://archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages [130 kB]
Get:12 http://archive.ubuntu.com/ubuntu xenial-updates/universe i386 Packages [127 kB]
Fetched 927 kB in 0s (1111 kB/s)
Reading package lists... Done
W: GPG error: http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Ubuntu_15.10 Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 977C43A8BA684223
W: The repository 'http://download.opensuse.org/repositories/isv:/ownCloud:/desktop/Ubuntu_15.10 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.
这不是我第一次在更新 Ownclous 时遇到问题，但这次我无法解决这个问题。你能帮忙吗？我如何明确验证 repo？PS 按照建议添加 GPG 密钥无法解决问题。我记得在安装客户端时添加了它。
答案1
现在有一个Owncloud 16.04 客户端存储库，因此请更新您的sources.list（只需替换15.10为16.04）并重试。
如果你尚未添加存储库的 GPG 密钥，请按照Owncloud客户端下载页面：
wget http://download.opensuse.org/repositories/isv:ownCloud:desktop/Ubuntu_16.04/Release.key
sudo apt-key add - < Release.key