当我使用sudo apt-get install squid此消息安装 Squid 时：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package squid is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'squid' has no installation candidate
我尝试在 55% 失败后升级：
W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/oneiric-backports/restricted/binary-i386/Packages 404 Not Found [IP: 91.189.91.14 80]
我该如何解决这个问题？
squid ×1