在使用apt install XXX时出现问题：
E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/f/fyba/libfyba0_4.1.1-6build1_amd64.deb Connection failed [IP: 185.125.190.39 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/universe/f/freexl/libfreexl1_1.0.5-3_amd64.deb Connection failed [IP: 91.189.91.39 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
由于没有配置好国内的镜像源。
解决方法：
①查看自己Ubuntu的版本：
lsb_release -a
（LSB是Linux Standard Base（Linux标准库）的缩写， lsb_release命令 用来与具体Linux发行版相关的Linux标准库信息）
获取版本号后进入：ubuntu | 镜像站使用帮助 | 清华大学开源软件镜像站 | Tsinghua Open Source Mirror
②选取自己版本对应的镜像源，然后进入apt文件夹
cd /etc/apt/
把之前的镜像源复制一份为001
sudo cp sources.list cources.list.001
再打开镜像源列表
sudo vim sources.list
按"a"进入编辑模式，把之前复制的镜像源粘到底下：
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-updates main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-updates main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-backports main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-backports main restricted universe multiverse
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-security main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-proposed main restricted universe multiverse
# deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ jammy-proposed main restricted universe multiverse
然后按ESC键，:wq，再按enter保存并退出
③然后更新apt：
sudo apt-get upgrade