http://www.36sign.com/blog/working/start-mongrel-solution.html给出了解决方案和问题分析
其实 我还是使用进入目录中运行"ruby script /server"来运行就没问题
问题：
jack@ubuntu:~$ ruby myrails/demo/script/server
=> Booting Mongrel (use 'script/server webrick' to force WEBrick)
=> Rails 2.2.3 application starting on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
!!! Path to log file not valid: log/mongrel.log
mongrel::start reported an error. Use mongrel_rails mongrel::start -h to get help.
Exiting