ubuntu中，出现Failed to fetch http://…..时，需要换源

问题描述：出现Failed to fetch http://…..

 

问题原因：一般是由于直接使用国外的源无法连接的原因导致的

 

解决方案：直接替换成国内的源即可

                        （1）执行备份命令：sudo cp /etc/apt/sources.list /etc/apt/sources.list.old

                    （2）打开文件：sudo vim /etc/apt/sources.list

                    （3）换源：复制源覆盖文件原来的内容（根据自己的网去尝试，选择最快的一个）

　　　　　   （4）更新源：sudo apt update        如果出现依赖问题-->sudo apt -f install

　　　　　   （5）更新软件：sudo apt upgrade

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以下是ubuntu20.04版本软件源 [另附其他版本地址：阿里云开源镜像站： http://mirrors.aliyun.com/]

                                                                               [清华大学：http://mirrors.tuna.tsinghua.edu.cn/  (IPv4+IPv6)]

                                                                               [中科大：http://mirrors.ustc.edu.cn/  (IPv4+IPv6)]

#添加阿里源

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

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

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

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

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

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

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

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

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

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

#添加清华源

deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse

# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse

deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse

# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse

deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse

# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse

deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse

# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse multiverse