今天部署一个系统，发现不能获取gem包，于是看看怎么回事
$ gem -v
1.3.6
$ gem update --system
JRuby limited openssl loaded. http://jruby.org/openssl
gem install jruby-openssl for full support.
Updating RubyGems
Updating rubygems-update
ERROR: While executing gem ... (Gem::GemNotFoundException)
could not find gem rubygems-update locally or in a repository
$ gem install rubygems-update
JRuby limited openssl loaded. http://jruby.org/openssl
gem install jruby-openssl for full support.
ERROR: could not find gem rubygems-update locally or in a repository
不知道为什么连不上，试试看，好像可以ping通
$ gem source *** CURRENT SOURCES *** http://rubygems.org/ $ ping rubygems.org PING rubygems.org (72.4.120.124) 56(84) bytes of data. 64 bytes from rubygems.org (72.4.120.124): icmp_seq=2 ttl=49 time=368 ms
于是决定下载，这时发现了问题
$ wget http://rubygems.org/downloads/rubygems-update-1.8.5.gem --2011-07-13 15:43:40-- http://rubygems.org/downloads/rubygems-update-1.8.5.gem 正在解析主机 rubygems.org... 72.4.120.124 Connecting to rubygems.org|72.4.120.124|:80... 已连接。 已发出 HTTP 请求，正在等待回应... 302 Found 位置：http://rubygems.org/gems/rubygems-update-1.8.5.gem [跟随至新的 URL] --2011-07-13 15:43:42-- http://rubygems.org/gems/rubygems-update-1.8.5.gem Reusing existing connection to rubygems.org:80. 已发出 HTTP 请求，正在等待回应... 302 Found 位置：http://production.cf.rubygems.org/gems/rubygems-update-1.8.5.gem [跟随至新的 URL] --2011-07-13 15:43:42-- http://production.cf.rubygems.org/gems/rubygems-update-1.8.5.gem 正在解析主机 production.cf.rubygems.org... 失败：域名解析暂时失败。 wget: unable to resolve host address `production.cf.rubygems.org'
进一步了解，发现是DNS污染，现在问题就简单了，查到对应的ip，然后修改
sudo vi /etc/hosts 216.137.53.162 production.cf.rubygems.org
下面就好办了
总结，在贵国，要考虑的问题有很多