Adding an SSH key to a server

بِسْمِ ٱللَّٰهِ ٱلرَّحْمَٰنِ ٱلرَّحِيمِ

This guide will explain how to add an SSH key to a remote server/container that has Linux installed on it. The user will then be able to connect from the host machine (where the key was generated) to the remote server.

The instructions should work on most Linux distros.

Generate your SSH key on your local PC

Run this command in any terminal software (like Yakuake, Konsole, Xterm or GNOME Terminal):

ssh-keygen -t rsa -b 4096 -C "add any comment you wish here"

Follow the prompts and remember to enter the full file-path for the key + its name when asked where to save the key to:

/path/to/.ssh/my_new_key

In the .ssh/ folder, 2 files should now exist:

• my_new_key

• my_new_key.pub

Add SSH key to remote server/container

Now connect to your remote server. Without an existing key, the way to connect to a remote server will be via a password, like:

ssh root@<some-ip-address>

It is advisable to restrict root access and create a user. In this guide we will assume the new user is called 'ubuntu'.

As the 'ubuntu' user run these commands:

cd
mkdir .ssh
chmod 700 .ssh/


cd .ssh/
touch authorized_keys
chmod 600 authorized_keys

Now open the my_new_key.pub file on your local PC.

Then run this command on the server to open and edit the authorized_keys file:

nano authorized_keys

Copy and paste the entire contents of my_new_key.pub into authorized_keys

Close the file by pressing CTRL + X and saving.

Test the connection by running this command on your local PC:

ssh -i ~/.ssh/my_new_key -p 22 ubuntu@<server-IP-address>

Bonus: adding the SSH info to your local PC SSH config file

On your local PC, open the following file .ssh/config using any text editor. Add the following text to this config file:

IdentitiesOnly yes

Host new-server
 HostName <server-IP-address>
 Port 22
 User ubuntu
 IdentityFile ~/.ssh/my_new_key


Host *
 ForwardAgent no
 IdentitiesOnly yes

It should now be possible to SSH to the server like so:

ssh ubuntu@new-server

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