http://wiki.ubuntu.com.cn/Unix%E5%91%BD%E4%BB%A4%E5%A4%A7%E5%85%A8#.E9.80.8F.E8.BF.87_PC_.E7.99.BB.E5.BD.95.E5.B7.A5.E4.BD.9C.E7.AB.99
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