最近我在旧机器上安装了旧版本的 Ubuntu。每当我尝试安装任何软件时，都会收到一条错误消息，说找不到它：
$ sudo apt-get install vlc
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package vlc
upgrade package-management support repository release-management
当我检查更新时，出现“无法下载存储库信息”错误。
这是详细信息下的内容：
W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources Hash Sum mismatch,
E: Some index files failed to download. They have been ignored, or old ones used instead.