Secure Shell (SSH)

Instructions for setting up the SSH Server on Linux

Installing SSH Server

Debian and Ubuntu

sudo apt install openssh-server

Securing you SSH Server

So far a very incomplete list of things to do to make the computer running SSH Server more secure. You will need root privileges to edit the sshd_config file. This file is found in different places, here is where I know where to look for it:

As a last resort you can use locate or find to find the config file.

After you make any changes to sshd_config you will need to reload the server. If you’re running systemd you’ll run

sudo systemctl restart sshd

And, if you’re running sysvinit you’ll run:

sudo service sshd restart

Changing the Default Port

This will confuse basic port sniffers that check to see if port 22 is open. Edit the sshd_config file and add or edit this line:

Port 12345  # Not 22!

Enable SSH Keys

Why do this? SSH Keys are probably more secure than your password, thus are harder to crack!

1. On your SSH Server enable SSH Key Logins by editing the sshd_config file. The default is to allow SSH Key Authentication, but make sure this line is included in yoru config: bash PubkeyAuthentication yes
2. NOTE: The rest of these steps will be run on your ssh client device (not the server)
3. Generate a Public-Private Key. Don’t do this if you already generated a key in this file as it will be overwritten. bash ssh-keygen -t rsa -b 2048 -f ~/.ssh/server_rsa_file
4. Copy the public key to your ssh server. This command will copy your public key into ~/.ssh/authorized_keys, but you can also do it manually. bash ssh-copy-id -i ~/.ssh/server_rsa_file.pub USER@HOST
5. Log into your server using your private key: bash ssh -i ~/.ssh/server_rsa_file USER@HOST

Disable passwords

This won’t allow a user to log in with their password. CAREFUL: You will need to enable SSH Keys before you do this! Edit the sshd_config file and add or edit this line:

PasswordAuthentication no