Ubuntu21.10 默认采用的官方提供的软件源，由于是国外的软件源，下载软件特别慢，下面将介绍怎样一步步将 Ubuntu21.10 软件源改为国内清华大学的软件源地址。详细步骤如下：
（1）备份 source.list 文件，然后修改 source.list 文件的权限，使之可以被编辑。命令如下：
hxstrive@course:~$ cd /etc/apt/
hxstrive@course:/etc/apt$ ls
apt.conf.d auth.conf.d preferences.d sources.list sources.list.d sources.list.save trusted.gpg.d
hxstrive@course:/etc/apt$ sudo cp -v sources.list sources.list.bak
'sources.list' -> 'sources.list.bak'
hxstrive@course:/etc/apt$ ls
apt.conf.d preferences.d sources.list.bak sources.list.save
auth.conf.d sources.list sources.list.d trusted.gpg.d
hxstrive@course:/etc/apt$ sudo chmod 774 sources.list（2）使用 gedit 编辑器编辑上面的 source.list 文件，命令如下：
hxstrive@course:/etc/apt$ sudo gedit sources.list（3）修改 source.list 文件，内容如下：
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ impish main restricted
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ impish-updates main restricted
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ impish universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ impish-updates universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ impish multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ impish-updates multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ impish-backports main restricted universe multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu impish-security main restricted
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu impish-security universe
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu impish-security multiverse（4）更新软件列表，命令如下：
hxstrive@course:~/Desktop/nginx-1.20.2$ sudo apt update
[sudo] password for hxstrive:
Get:1 http://mirrors.tuna.tsinghua.edu.cn/ubuntu impish InRelease [270 kB]
Get:2 http://mirrors.tuna.tsinghua.edu.cn/ubuntu impish-updates InRelease [115 kB]
...
Get:95 http://mirrors.tuna.tsinghua.edu.cn/ubuntu impish-security/multiverse amd64 c-n-f Metadata [116 B]
Fetched 48.1 MB in 39s (1,222 kB/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
6 packages can be upgraded. Run 'apt list --upgradable' to see them.（5）更新软件，命令如下：
hxstrive@course:~/Desktop/nginx-1.20.2$ sudo apt upgrade
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
...
Setting up fonts-opensymbol (2:102.12+LibO7.2.5-0ubuntu0.21.10.3) ...
Processing triggers for hicolor-icon-theme (0.17-2) ...
Processing triggers for libc-bin (2.34-0ubuntu3.2) ...
Processing triggers for man-db (2.9.4-2) ...
Processing triggers for dbus (1.12.20-2ubuntu2) ...
Processing triggers for fontconfig (2.13.1-4.2ubuntu3) ...到这里就配置完了！！！
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