在最后一周或更长时间，运行sudo apt-get update以错误告终：
Reading package lists... Done
E: Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/xenial/main/dep11/Components-amd64.yml
Could not open file /var/lib/apt/lists/partial/au.archive.ubuntu.com_ubuntu_dists_xenial_main_dep11_Components-amd64.yml.gz - open (13: Permission denied) [IP: 202.158.214.106 80]
E: Failed to fetch http://au.archive.ubuntu.com/ubuntu/dists/xenial-backports/main/dep11/icons-64x64.tar Could not open file /var/lib/apt/lists/partial/au.archive.ubuntu.com_ubuntu_dists_xenial-backports_main_dep11_icons-64x64.tar.gz - open (13: Permission denied) [IP: 202.158.214.106 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
在浏览器地址栏中输入 2 个指定 url 中的任何一个会导致“找不到文件”(404) 错误 - 但如果我附加.gz到两个地址，则可以下载相应的文件。
但是，下载了 2 个文件后，我不知道如何（或是否）可以使用它们。
寻求有关如何最好地进行的建议。