Ubuntu Config SSH service

First try ssh localhost

ssh localhost

If the SSH service is not started, the following error will be reported:

ssh: connect to host localhost port 22: connection refused

Set SSH password-free login (optional)

This step sets the password-free login by setting the public and private keys. You can skip this step if the server is logged in with a username and password.
Running the following command generates a bunch of keys id_rsa and id_rsa.pub in the ~/.ssh/directory:

ssh-keygen

To enter the following prompt information, the key pair will be generated in the default location ~/.ssh/directory, and we set passphrase to empty, that is, no password login.
Use the following command to join the newly generated public key to the authorized key list file Authorized_keys (because there is no Authorized_keys file at the beginning, so use the CP command here):

cp ~/.ssh/id_isa.pub ~/.ssh/authorized_keys

Make sure that the. SSH directory and the Authorized_keys file have only the user's own Write permission, otherwise the validation is not valid

chomd 600 ~/.ssh/authorized_keyschmod 700 ~/.ssh

Open SSH Service

Configure the non-secret login still cannot ssh localhost, because Ubuntu default does not install and open the SSH server, therefore, we also need:
1. Determine the installation of sshd

sudo apt-get install openssh-server

2. Start sshd

sudo net start sshd

3. Check the firewall settings and turn off the firewall

sudo nfw disable

4. Verify the success, run the following command

ssh localhost

Sometimes although successful, but still will appear connection refused problem, this is, need to check whether the sshd process is started.
Run the following command to see if there is an sshd process:

ps -e | grep ssh

Sometimes although you can see the sshd, but still cannot connect successfully, this is the need to restart SSH:

sudo service ssh restart

Then connect again.

Ubuntu Config SSH service