Linux更新源问题：
当使用apt-get安装、更新某些软件时，有时会出现失败的情况，提示信息可能为制定页面访问出错。执行sudo apt-get update命令同样失败。这种情况可能是Linux更新源过期所致。
解决方法：
更新Linux的软件源，修改 /etc/apt/sources.list文件，将内容更换为新的软件更新源，如163国内镜像点：
deb http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ trusty-backports main restricted universe multiverse
保存文件后，再次执行sudo apt-get update，随后即可正常安装、更新软件。