检查是否安装了ssh服务

在windows安装虚拟linux的ubuntu桌面版本，默认并没有安装ssh服务，如果通过ssh链接ubuntu，需要自己手动安装ssh-server。

#判断是否安装ssh服务，可以通过如下命令进行：
YR@YR-virtual-machine:~$ ssh localhost ssh
YR@YR-virtual machine:~$ ssh localhost 
ssh: connect to host localhost port 22: Connection refused
# 如上表示没有安装，可以通过apt安装
YR@YR-virtual machine:~$  sudo apt-get install openssh-server 

#如果程序Ubuntu安装ssh时出现如下错误：
E:软件包 openssh-server 还没有可供安装的候选者
#解决方案：更新apt-get
sudo apt-get update
sudo apt-get install openssh-server

#检查open-server是否安装成功-1
ps -e|grep ssh 
# 如下表示成功
   1604 ?        00:00:00 ssh-agent
   4562 ?        00:00:00 sshd

#检查open-server是否安装成功-2
ssh localhost
# 如下表示成功
The authenticity of host 'localhost (127.0.0.1)' can't be established.
ECDSA key fingerprint is SHA256:4t5fOPQzUobT1MoTwhyJDYc/5ycaSOB+juJyG6lf3N4.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.
YR@localhost's password: