1.修改软件源

Ubuntu软件源默认是Ubuntu服务器，速度比较慢，可以通过换国内软件源提升下载速度和使用体验。

1.1查看软件源版本

• Ubuntu不同的版本对应软件源版本名称也不同，可用通过如下命令查询当前系统的版本名：

jun@jun-VirtualBox:~$ lsb_release -c
Codename:       focal
jun@jun-VirtualBox:~$

• Ubuntu版本名与系统名对应关系：

1.2备份文件

避免格式修改错误导致无法使用，建议备份一个文件

jun@jun-VirtualBox:~$ sudo cp /etc/apt/sources.list /etc/apt/sources.listbk

1.3修改成国内软件源

国内软件源参考Ubuntu20.04软件源更换 - 知乎 (zhihu.com)
清华软件源

• 图形界面Ubuntu修改文件，图形界面编辑器可以使用ctrl+v，更方便，自带的vim有方向键无法使用

jun@jun-VirtualBox:~$ sudo gedit /etc/apt/sources.list

• 使用vim修改文件

jun@jun-VirtualBox:~$ sudo vim /etc/apt/sources.list

以下三个源供参考，更多源参考： 中国Linux源镜像站大全

#focal 版本
#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

#网易源
deb http://mirrors.163.com/ubuntu/ focal main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-security main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-security main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-updates main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-proposed main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-proposed main restricted universe multiverse
deb http://mirrors.163.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://mirrors.163.com/ubuntu/ focal-backports main restricted universe multiverse

#清华源
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse

可以在文本编辑器修改好以后一次复制过去，注意替换软件源时只需要替换地址即可。如把阿里源替换成清华源，只需要把"mirrors.aliyun.com"替换成"mirrors.tuna.tsinghua.edu.cn"

2.重新安装vim

2.1更新软件源

jun@jun-VirtualBox:~$ sudo apt update 

2.2删除vim

jun@jun-VirtualBox:~$ sudo apt remove vim

2.3安装新版本的vim

jun@jun-VirtualBox:~$ sudo apt install vim
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  ctags vim-doc vim-scripts
The following NEW packages will be installed:
  vim
0 upgraded, 1 newly installed, 0 to remove and 179 not upgraded.
Need to get 1,239 kB of archives.

直接输入vim可以查看版本号

vim 版本号

3.关闭图形界面

参考ubuntu20.04 关闭图形界面

• 关闭用户图形界面，使用tty登录。

sudo systemctl set-default multi-user.target
sudo reboot

• 开启用户图形界面。

sudo systemctl set-default graphical.target
sudo reboot

4.安装ssh服务

sudo apt update
sudo apt install openssh-server

5.ssh服务启动与停止

5.1查看当前运行状态

使用sudo systemctl status ssh查看ssh服务运行状态，如下图所示，ssh.service前面标了一个黄色灯，active 状态显示为active（running）表示已经在运行了，可以通过ssh xxx@xxx.xxx.xxx.xxx连接Ubuntu。

ssh运行状态

jun@jun-VirtualBox:~$ sudo systemctl status ssh
[sudo] password for jun:
● ssh.service - OpenBSD Secure Shell server
     Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
     Active: active (running) since Sun 2022-01-16 13:27:47 CST; 1min 2s ago
       Docs: man:sshd(8)
             man:sshd_config(5)
    Process: 5274 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCESS)
   Main PID: 5275 (sshd)
      Tasks: 1 (limit: 4651)
     Memory: 2.6M
     CGroup: /system.slice/ssh.service
             └─5275 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups

1月 16 13:27:47 jun-VirtualBox systemd[1]: Starting OpenBSD Secure Shell server...
1月 16 13:27:47 jun-VirtualBox sshd[5275]: Server listening on 0.0.0.0 port 22.
1月 16 13:27:47 jun-VirtualBox sshd[5275]: Server listening on :: port 22.
1月 16 13:27:47 jun-VirtualBox systemd[1]: Started OpenBSD Secure Shell server.
1月 16 13:27:55 jun-VirtualBox sshd[5279]: Accepted password for jun from 7.249.167.187 port 60754 ssh2
1月 16 13:27:55 jun-VirtualBox sshd[5279]: pam_unix(sshd:session): session opened for user jun by (uid=0)
jun@jun-VirtualBox:~$

5.2启动ssh服务

sudo systemctl start ssh

5.3停止ssh服务

sudo systemctl stop ssh

5.4重启ssh服务

sudo systemctl restart ssh