在ubuntu下，设置/etc/apt/sources.list之后，运行
sudo apt-get update
，要是遇到类似这样的报错：
Ign http://us.archive.ubuntu.com raring-backports/restricted Translation-en_US
Ign http://us.archive.ubuntu.com raring-backports/universe Translation-en_US
Fetched 166 kB in 32s (5,075 B/s)
W: Failed to fetch bzip2:/var/lib/apt/lists/partial/extras.ubuntu.com_ubuntu_dists_raring_main_binary-i386_Packages Hash Sum mismatch
W: Failed to fetch bzip2:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_raring_universe_source_Sources Hash Sum mismatch
W: Failed to fetch bzip2:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_raring_main_binary-i386_Packages Hash Sum mismatch
W: Failed to fetch bzip2:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_raring_universe_binary-i386_Packages Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old ones used instead.
Ign http://us.archive.ubuntu.com raring-backports/universe Translation-en_US
，在/etc/apt/sources.list文件中把raring-backports/universe相关的内容注释掉再继续就可以了，比如下面的两行：
deb http://mirrors.163.com/ubuntu/ raring universe
deb-src http://mirrors.163.com/ubuntu/ raring universe
注释掉（先注释掉下面一行，继续，不行的话再注释掉第一行），就可以了