网络上有一些手册，但都认为debian仍然维护6.0的镜像
然而，目前 debian repos 没有受到挤压。
那么如果镜像不可用，如何将当前服务器更新为可维护的内容？
apt-get update
Hit http://security.debian.org squeeze/updates Release.gpg
Ign http://security.debian.org/ squeeze/updates/contrib Translation-en
Ign http://security.debian.org/ squeeze/updates/contrib Translation-en_GB
Ign http://security.debian.org/ squeeze/updates/main Translation-en
Ign http://security.debian.org/ squeeze/updates/main Translation-en_GB
Ign http://security.debian.org/ squeeze/updates/non-free Translation-en
Ign http://security.debian.org/ squeeze/updates/non-free Translation-en_GB
Hit http://security.debian.org squeeze/updates Release
Hit http://security.debian.org squeeze/updates/main Sources
Hit http://security.debian.org squeeze/updates/contrib Sources
Hit http://security.debian.org squeeze/updates/non-free Sources
Hit http://security.debian.org squeeze/updates/main amd64 Packages
Hit http://security.debian.org squeeze/updates/contrib amd64 Packages
Hit http://security.debian.org squeeze/updates/non-free amd64 Packages
Ign http://ftp.us.debian.org squeeze Release.gpg
Ign http://ftp.us.debian.org/debian/ squeeze/contrib Translation-en
Ign http://ftp.us.debian.org/debian/ squeeze/contrib Translation-en_GB
Ign …