Ubuntu 替换源

安装ubuntu 各个网站上都建议更新源，以便能快速的下载，但baidu后将找到的源复制到

/etc/apt/source.list

sudo apt-get install 时出现各种问题，提示版本太老等问题

错误提示：

apt install 提示版本过老

sudo apt-get install g++时提示版本太老

sunhuihui@Huizi-PC:/etc/apt$ sudo apt-get install g++
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 g++ : Depends: g++-4.8 (>= 4.8.2-5~) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

以下是百度到的source.list

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

问题原因分析

查看了一些文章才发现，主要是这些source.list与系统版本相比太老了

sunhuihui@Huizi-PC:/etc/apt$ lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.1 LTS
Release:        18.04
Codename:       bionic

其实每一条内容都是有固定格式的：

deb-src http://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse  

trusty： 就是每个linux的版本号，如果你的ubuntu18.04但是使用了老的源，必然会提示错误；

各版本代号参考：

Ubuntu 12.04 (LTS)代号为precise。

Ubuntu 14.04 (LTS)代号为trusty。

Ubuntu 15.04 代号为vivid。

Ubuntu 15.10 代号为wily。

Ubuntu 16.04 (LTS)代号为xenial。

参考个版本代号可以发现，18.04的版本使用了trusty(14.04的源)这样必然会出现各种更新问题

替换为最新源

那么只需要将源文本中的代号改为当前版本对应的代号即可：

deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse

最后，更新源并生效

sudo apt update
sudo apt upgrade

建议

修改源时，建议通过update-manager 通过GUI界面修改选择中国–阿里或其它的服务器