Ubuntu Linux install OpenSSH server

How to install SSH server in Ubuntu

The procedure to install a ssh server in Ubuntu Linux is as follows:

1. Open the terminal application for Ubuntu desktop.
2. For remote Ubuntu server you must use BMC or KVM or IPMI tool to get console access.
3. Type command:$ sudo apt-get install openssh-server
4. Enable the ssh service by typing:$ sudo systemctl enable ssh
## OR enable and start the ssh service immediately ##
$ sudo systemctl enable ssh --now
5. Start the ssh service by typing:$ sudo systemctl start ssh
6. Test it by login into the system using:$ ssh userName@Your-server-name-IP
$ ssh ec2-user@ec2-aws-ip-here

Let us see all Ubuntu OpenSSH server installation steps in details with config options using remote console or local terminal.

1. Login to remote server using bmc/ipmi/kvm over IP (optional)

I am using OpenPOWER based system called Talos II from Raptor Computing Systems. It is a PowerPC (ppc/ppc64le) based architecture. After a fresh installation of Ubuntu Linux (ppc64le), I found does not come with SSH server installed by default. So here is how to login to bmc server to gain access to the serial console:
$ ssh root@power9-bmc
Run obmc-console-client to get console access to the Ubuntu server console:
# obmc-console-client

2. Ubuntu Linux install OpenSSH server

First update the system using the apt command or apt-get command:
$ sudo apt update
$ sudo apt upgrade

Installing sshd server on Ubuntu Linux

To install openssh-server package, run:
$ sudo apt install openssh-server

Click to enlarge an image

3. Verify that ssh service running

Type the following systemctl command:
$ sudo systemctl status ssh

If not running enable the ssh server and start it as follows by typing the systemctl command:
$ sudo systemctl enable ssh
$ sudo systemctl start ssh

Synchronizing state of ssh.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable ssh
Created symlink /etc/systemd/system/sshd.service ? /lib/systemd/system/ssh.service.

4. Configure firewall and open port 22

You must configure the Ubuntu Linux firewall called ufw. Here is how open or allow port 22 when using ufw on Ubuntu:
$ sudo ufw allow ssh
$ sudo ufw enable
$ sudo ufw status
See our “setting up ufw firewall on Ubuntu” guide for more info.

5. Test it

Now you can login from your desktop computer powered by Linux, *BSD, macOS, MS-Windows (putty client) or Unix-like system using the ssh command:
$ ssh vivek@server-ip
$ ssh vivek@power9

You can install copy and install the public key using ssh-copy-id command for password less login:
$ ssh-copy-id vivek@power9
See “SSH Public Key Based Authentication on a Linux/Unix server” for more info.

Ssh config file

One can create shortcuts for ssh login / client options. For example create a file named ~/.ssh/config as follows:
$ nano ~/.ssh/config
OR
$ vi $HOME/.ssh/config
Append the following to login into my EC2 Ubuntu server at AWS cloud:

Host web01
        HostName aws-ec2-www-server1.cyberciti.biz
        Port 22
        IdentityFile  ~/.ssh/AWS_EC2_Virginia_US_East_Ubuntu_Boxes.pem
        User ubuntu

To log in simply type:
$ ssh web01
See “OpenSSH Config File Examples” for more info.

Conclusion

In this tutorial, you learn how to install the OpenSSH server application at a terminal prompt. Although instructions tested for Power9 (ppc64le) architecture, they should work on Intel AMD64 or ARAM64 server as well. For more info see OpenSSH home page here and how to secure OpenSSH server tutorial here. Make sure you read manual pages too using the man command:
$ man sshd_config