【解决场景】
1.无法找到软件包
apt-get install : E: Unable to locate package xxx
软件中心安装时显示：There isn't a software package called "Smile" in your current software resources
2.可以找到软件包，但无法自动安装依赖
The following packages have unmet dependencies:
package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed
E: Unable to correct problems, you have held broken packages.
【解决方案】
以上问题都由源没有添加 安装源导致的。
源所在位置：/etc/opt/sources.list
安装源模板：
deb MIRROR_URL/ubuntu/ UBUNTURELEASENAME main restricted universe multiverse
deb MIRROR_URL/ubuntu/ UBUNTURELEASENAME-security main restricted universe multiverse
deb MIRROR_URL/ubuntu/ UBUNTURELEASENAME-updates main restricted universe multiverse
deb MIRROR_URL/ubuntu/ UBUNTURELEASENAME-proposed main restricted universe multiverse
deb MIRROR_URL/ubuntu/ UBUNTURELEASENAME-backports main restricted universe multiverse
deb-src MIRROR_URL/ubuntu/ UBUNTURELEASENAME main restricted universe multiverse
deb-src MIRROR_URL/ubuntu/ UBUNTURELEASENAME-security main restricted universe multiverse
deb-src MIRROR_URL/ubuntu/ UBUNTURELEASENAME-updates main restricted universe multiverse
deb-src MIRROR_URL/ubuntu/ UBUNTURELEASENAME-proposed main restricted universe multiverse
deb-src MIRROR_URL/ubuntu/ UBUNTURELEASENAME-backports main restricted universe multiverse
国内镜像地址：替换模板中的 MIRROR_URL
http://mirrors.sohu.com
http://mirrors.163.com
http://mirrors.aliyun.com
http://ubuntu.uestc.edu.cn
ubuntu版本名：替换UBUNTURELEASENAME, eg : xenial
lsb_release -a
root@ubuntu:/etc/apt# lsb_release -a
No LSB modules are available.
Distributor ID:Ubuntu
Description:Ubuntu 16.04 LTS
Release:16.04
Codename:<strong>xenial #版本名</strong>
安装源示例：
使用时只需要替换 trusty为相应的ubuntu版本名，保存为sources.list，并替换/etc/opt/sources.list即可，注意要使用root权限 sudo cp sources.list /etc/opt/sources.list
# /etc/apt/sources.list
# cn
deb http://mirrors.sohu.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.sohu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.sohu.com/ubuntu/ trusty-backports main restricted universe multiverse
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
deb http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
deb http://ubuntu.uestc.edu.cn/ubuntu/ trusty main restricted universe multiverse
deb http://ubuntu.uestc.edu.cn/ubuntu/ trusty-security main restricted universe multiverse
deb http://ubuntu.uestc.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse
deb http://ubuntu.uestc.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse
deb http://ubuntu.uestc.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ trusty main restricted universe multiverse
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse
# office
deb http://cn.archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ trusty-security main restricted universe multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://cn.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
# beta
deb http://cn.archive.ubuntu.com/ubuntu/ trusty-proposed main restricted universe multiverse
# src
deb-src http://cn.archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://cn.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
# beta
deb-src http://cn.archive.ubuntu.com/ubuntu/ trusty-proposed main restricted universe multiverse
# US
deb http://us.archive.ubuntu.com/ubuntu/ trusty main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty main restricted
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates main restricted
deb http://us.archive.ubuntu.com/ubuntu/ trusty universe
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty universe
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe
deb http://us.archive.ubuntu.com/ubuntu/ trusty multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty multiverse
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
deb http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb http://archive.canonical.com/ubuntu trusty partner
deb-src http://archive.canonical.com/ubuntu trusty partner
deb http://us.archive.ubuntu.com/ubuntu/ trusty-security main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-security main restricted
deb http://us.archive.ubuntu.com/ubuntu/ trusty-security universe
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-security universe
deb http://us.archive.ubuntu.com/ubuntu/ trusty-security multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-security multiverse