How to completely uninstall, install and start the ssh service

via command  ssh localhost

You can check whether the ssh service has been installed

As shown in the figure below , the ssh service has been installed

If the following situation occurs, it means that the ssh service has not been installed on the machine

ssh localhost

ssh: connect to host localhost port 22: Connection refused

First, let's talk about how to uninstall the ssh service .

1. Completely uninstall the ssh service

            apt-get purge openssh-server

2. Update the source list (the latest SSH service can be installed)

           sudo apt-get update

3. Install SSH service

          sudo apt-get install openssh-server

      Enter the following command and the system will automatically install the ssh service.

4. The first step after installing the SSH service is to open the SSH service sudo /etc/init.d/ssh start

           sudo /etc/init.d/ssh start

5. After startup, you can use the following command to check whether the service is started correctly

             ps -e|grep ssh   

         6212 ? 00:00:00 sshd 

6. After the startup is complete, you can modify the ssh configuration
                gedit /etc/ssh/sshd_config

7. Next is Some errors and solutions

        PS1: You need to enter the passcode for the first connection, and you don't need to enter the passcode in the future. Is it safer to enter the SSH account password without entering it?

        PS2: Restrict IP access to SSH, the server will be more secure.
                vi /etc/hosts.allow

                sshd:172.16.XX:allow #Write 172.16.XX/172.16.0 (segment) in the last line
                vi /etc/hosts.deny

                 sshd:ALL

         PS3: Assuming you want to delete the public key, in SECURECRT Do not select the public key when connecting, and then enter the SSH configuration file and modify it as follows:

                  1. Comment #AuthorizedKeysFile %h/.ssh/authorized_keys

                  2. PasswordAuthentication yes

        PS4: When using SecureCRT to connect, it prompts: unable to authenticate using any of the configured authentication methods

                Solution: PasswordAuthentication yes

If there is an error, please correct me.