具體過程如下：
1、InstantRails-2.0安裝后，在配置環(huán)境變量path中配置ruby/bin目錄（如果系統(tǒng)中有多個(gè)RUBY，執(zhí)行命令行的時(shí)候系統(tǒng)認(rèn)的就是path中的）
2、進(jìn)入DOS命令行，執(zhí)行g(shù)em update --system，結(jié)果
Updating RubyGems...
ERROR: While executing gem ... (Gem::RemoteSourceException)
HTTP Response 302 fetching http://rubygems.org/yaml
這是因?yàn)間em的配置過低，無法進(jìn)行遠(yuǎn)程更新，執(zhí)行g(shù)em -v 發(fā)現(xiàn)是1.0.1
3、從下面這個(gè)地址下載 rubygems-update-1.3.7.gem，http://rubyforge.org/frs/download.php/70695/rubygems-update-1.3.7.gem
然后DOS命令進(jìn)行該文件所在的目錄，執(zhí)行g(shù)em install --local rubygems-update-1.3.7.gem，出現(xiàn)信息
Successfully installed rubygems-update-1.3.7
1 gem installed
Installing ri documentation for rubygems-update-1.3.7...
Installing RDoc documentation for rubygems-update-1.3.7...
Could not find main page README
Could not find main page README
Could not find main page README
Could not find main page README
執(zhí)行g(shù)em -v查看，發(fā)現(xiàn)并沒有更新成功，Could not find main page README是什么意思我沒弄明白，但是我從http://production.s3.rubygems.org/yaml上發(fā)現(xiàn)這么一句
If you have an older version of RubyGems installed, then you can still
do it in two steps:
$ gem install rubygems-update # again, might need to be admin/root
$ update_rubygems # ... here too
我照著再執(zhí)行 update_rubygems，接著出現(xiàn)的信息很多，就不帖出來，再執(zhí)行g(shù)em -v，發(fā)現(xiàn)更新成功，已經(jīng)是1.3.7了
這一步是一切成功的源泉！！！！！！
4、接著再執(zhí)行g(shù)em update --system，提示
Updating RubyGems
Nothing to update
這是為什么我不明白，請高手指點(diǎn)一下
5、再執(zhí)行g(shù)em update rails --include-dependencies，提示信息
Updating installed gems
Updating rails
ERROR: Error installing rails:
actionpack requires rack (~> 1.0.0, runtime)
Gems updated: activesupport, activerecord
Installing ri documentation for activesupport-2.3.3...
Installing ri documentation for activerecord-2.3.3...
Installing RDoc documentation for activesupport-2.3.3...
Installing RDoc documentation for activerecord-2.3.3...
執(zhí)行rails -v，發(fā)現(xiàn)還是2.0.2沒有更新成功，根據(jù)actionpack requires rack (~> 1.0.0, runtime)，應(yīng)該是actionpack 需要1.0.0版本的rack
6、執(zhí)行g(shù)em install rack -v=1.0.0
Successfully installed rack-1.0.0
1 gem installed
Installing ri documentation for rack-1.0.0...
Installing RDoc documentation for rack-1.0.0...
更新成功
7、再次執(zhí)行 gem update rails --include-dependencies
出現(xiàn)信息
Updating installed gems
Updating rails
Successfully installed rake-0.8.7
Successfully installed activesupport-2.3.8
Successfully installed activerecord-2.3.8
Successfully installed rack-1.1.0
Successfully installed actionpack-2.3.8
Successfully installed actionmailer-2.3.8
Successfully installed activeresource-2.3.8
Successfully installed rails-2.3.8
Gems updated: rake, activesupport, activerecord, rack, actionpack, actionmailer, activeresource, rails
Installing ri documentation for rake-0.8.7...
Installing ri documentation for activesupport-2.3.8...
Installing ri documentation for activerecord-2.3.8...
Installing ri documentation for rack-1.1.0...
Installing ri documentation for actionpack-2.3.8...
Installing ri documentation for actionmailer-2.3.8...
Installing ri documentation for activeresource-2.3.8...
Installing ri documentation for rails-2.3.8...
Installing RDoc documentation for rake-0.8.7...
Installing RDoc documentation for activesupport-2.3.8...
Installing RDoc documentation for activerecord-2.3.8...
Installing RDoc documentation for rack-1.1.0...
Installing RDoc documentation for actionpack-2.3.8...
Installing RDoc documentation for actionmailer-2.3.8...
Installing RDoc documentation for activeresource-2.3.8...
Installing RDoc documentation for rails-2.3.8...
執(zhí)行rails -v，發(fā)現(xiàn)已更新成功
總結(jié)：rails更新有兩種方式：1、聯(lián)機(jī)更新;2本地更新
聯(lián)機(jī)更新過程中如果出現(xiàn)HTTP Response 302 fetching http://rubygems.org/yaml無法更新，有兩種情況
一是gem的版本過低，二是與服務(wù)器的連接不通
此時(shí)可以試著加入其他服務(wù)器地址
gem source -l 查看列表
gem source -a http://rubygems.org 加入新的服務(wù)器地址
或者直接gem install rubygems-update --source http://rubygems.org
本地更新需要下載相應(yīng)的gem包，版本需與要更新的rails版本對應(yīng)，同時(shí)安裝順序有要求，因此gem包之間有依賴關(guān)系
順序從上面的顯示信息中可以看出來
Successfully installed rake-0.8.7
Successfully installed activesupport-2.3.8
Successfully installed activerecord-2.3.8
Successfully installed rack-1.1.0
Successfully installed actionpack-2.3.8
Successfully installed actionmailer-2.3.8
Successfully installed activeresource-2.3.8
Successfully installed rails-2.3.8
至于gem包的下載地址都在http://rubyforge.org/，但是有些項(xiàng)目的并不好找到，可以在google中直接搜索，就能找到在http://rubyforge.org/中的地址。
一天，一個(gè)月，一年。總有一天會變得不一樣。