使用 apt update 报错
The following NEW packages will be installed:
autopoint dh-autoreconf libappstream4 libstemmer0d
The following packages will be upgraded:
apport apport-gtk appstream debhelper libarchive13 python3-apport
python3-problem-report
7 upgraded, 4 newly installed, 0 to remove and 0 not upgraded.
Need to get 1,914 kB of archives.
After this operation, 1,555 kB of additional disk space will be used.
WARNING: The following packages cannot be authenticated!
libappstream4 appstream dh-autoreconf debhelper libarchive13
E: There were unauthenticated packages and -y was used without --allow-unauthenticated
apt-key utility
apt-key用于管理apt用于验证软件包的密钥列表。 已经使用这些密钥验证的软件包将被视为可信。 使用Ubuntu归档密钥的密钥环更新本地密钥环，并从密钥环中移除不再有效的归档密钥。
解决方法
$ sudo apt-key update
$ sudo apt-get update
