當使用apt-get update更新源時，出現下面“Hash Sum mismatch”的報錯，具體如下：
root@localhost:~# apt-get update
......
......
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/main/source/Sources Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/restricted/source/Sources Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/universe/source/Sources Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/multiverse/source/Sources Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/main/binary-amd64/Packages Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/restricted/binary-amd64/Packages Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/universe/binary-amd64/Packages Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/multiverse/binary-amd64/Packages Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/main/binary-i386/Packages Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/restricted/binary-i386/Packages Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/universe/binary-i386/Packages Hash Sum mismatch
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/precise/multiverse/binary-i386/Packages Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old ones used instead.
產生原因：
所使用的網絡供應商，有些會設置一些透明緩存，以增加網絡內部速度，減少出口的流量，所獲取的某些文件不是源服務器上的真正文件，是從緩存中獲取的，當緩存中獲取的一些校驗信息跟源中不一致的時候，自然提示校驗失敗，無法繼續更新。
解決辦法：
1）刪掉/var/lib/apt/lists 這個目錄下的東西
sudo rm -fR /var/lib/apt/lists/*
2）新建相應文件夾
sudo mkdir /var/lib/apt/lists/partial
3）重新update
sudo apt-get update