when I try to upgrade the system ,it always failed.
W:无法下载 http://cn.archive.ubuntu.com/ubuntu/dists/precise-updates/main/binary-i386/Packages 404 Not Found
, W:无法下载 gzip:/var/lib/apt/lists/partial/cn.archive.ubuntu.com_ubuntu_dists_precise_universe_i18n_Translation-en Encountered a section with no Package: header
, E:Some index files failed to download. They have been ignored, or old ones used instead.
what should i do ?