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  1. Generate Ssh Key Putty
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  3. Ubuntu Generate Ssh Key Pair
am a new Ubuntu 18.04 LTS user and I would like to setup ssh public key authentication. How do I set up ssh keys based authentication on Ubuntu Linux 18.04 LTS server? How do I set up SSH keys on an Ubuntu Linux 18.04 LTS server? In Ubuntu 18.04 LTS, how do I set up public key authentication?

Create an SSH key. Follow these steps if you don't already have an SSH key for an account. If you do have an SSH key and you want to generate another key, you'll have to use the terminal because you can't use Sourcetree to create a second key. Creating an SSH key looks something like this: From the Sourcetree menu, select Preferences. The.pub file is your public key, and the other file is the corresponding private key. If you don’t have these files (or you don’t even have a.ssh directory), you can create them by running a program called ssh-keygen, which is provided with the SSH package on Linux/macOS systems and comes with Git for Windows.

Introduction

Aug 09, 2018 Generate SSH Keys on Windows 10 with PuTTY. To generate a key pair with the PuTTY key generator, simply run andputtygen.exe click the Generate button in the window that appears. You will be asked to move the mouse and press keys to improve the random number generation at the heart of SSH security. Aug 09, 2018  Generate SSH Keys on Windows 10 with PuTTY. To export the private key, select Export OpenSSH key from the Conversions menu. To export the public key, click Save public key from the main window. To generate the public/private key pair, enter this in the Command Prompt: ssh-keygen At the first prompt, “Enter file in which to save the key,” press Enter to save it in the default location.

: OpenSSH is a free and open source client/server technology for secure remote login. It is an implementation of the SSH protocol. OpenSSH divided into sshd (server) and various client tools such as sftp, scp, ssh and more. One can do remote login with OpenSSH either using password or combination of private and public keys named as public key based authentication. It is an alternative security method for user passwords. This method is recommended on a VPS, cloud, dedicated or even home-based server or laptop. This page shows how to set up SSH keys on Ubuntu 18.04 LTS server.
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Ubuntu 18.04 Setup SSH Public Key Authentication

The procedure to set up secure ssh keys on Ubuntu 18.04:

  1. Create the key pair using ssh-keygen command.
  2. Copy and install the public key using ssh-copy-id command.
  3. Add yourself to sudo admin account on Ubuntu 18.04 server.
  4. Disable the password login for root account on Ubuntu 18.04.

Sample set up for SSH Keys on Ubuntu 18.04


Where,

  • 202.54.1.55 – You store your public key on the remote hosts and you have an accounts on this Ubuntu Linux 18.04 LTS server.
  • Linux/macbook laptop – Your private key stays on the desktop/laptop/computer (or local server) you use to connect to 202.54.1.55 server. Do not share or give your private file to anyone.

In public key based method you can log into remote hosts and server, and transfer files to them, without using your account passwords. Feel free to replace 202.54.1.55 and client names with your actual setup. Enough talk, let’s set up public key authentication on Ubuntu Linux 18.04 LTS.

How to create the RSA/ed25519 key pair on your local desktop/laptop

Open the Terminal and type following commands if .ssh directory does not exists:
$ mkdir -p $HOME/.ssh
$ chmod 0700 $HOME/.ssh

Next generate a key pair for the protocol, run:
$ ssh-keygen
OR
$ ssh-keygen -t rsa 4096 -C 'My key for Linode server'
These days ED25519 keys are favored over RSA keys when backward compatibility is not needed:
$ ssh-keygen -t ed25519 -C 'My key for Linux server # 42'

How to install the public key in Ubuntu 18.04 remote server

The syntax is as follows:
ssh-copy-id your-user-name@your-ubuntu-server-name
ssh-copy-id -i ~/.ssh/file.pub your-user-name@your-ubuntu-server-name

For example:
## for RSA KEY ##
ssh-copy-id -i $HOME/.ssh/id_rsa.pub user@202.54.1.55
## for ED25519 KEY ##
ssh-copy-id -i $HOME/.ssh/id_ed25519.pub user@202.54.1.55
## install SSH KEY for root user ##
ssh-copy-id -i $HOME/.ssh/id_ed25519.pub root@202.54.1.55

I am going to install ssh key for a user named vivek (type command on your laptop/desktop where you generated RSA/ed25519 keys):
$ ssh-copy-id -i ~/.ssh/id_ed25519.pub vivek@202.54.1.55

Generate Ssh Key Putty

Test it

Now try logging into the Ubuntu 18.04 LTS server, with ssh command from your client computer/laptop using ssh keys:
$ ssh your-user@your-server-name-here
$ ssh vivek@202.54.1.55

What are ssh-agent and ssh-add, and how do I use them on Ubuntu 18.04?

To get rid of a passphrase for the current session, add a passphrase to ssh-agent (see ssh-agent command for more info) and you will not be prompted for it when using ssh or scp/sftp/rsync to connect to hosts with your public key. The syntax is as follows:
$ eval $(ssh-agent)
Type the ssh-add command to prompt the user for a private key passphrase and adds it to the list maintained by ssh-agent command:
$ ssh-add
Enter your private key passphrase. Now try again to log into vivek@202.54.1.55 and you will NOT be prompted for a password:
$ ssh vivek@202.54.1.55

How to disable the password based login on a Ubuntu 18.04 server

Login to your server, type:
## client commands ##
$ eval $(ssh-agent)
$ ssh-add
$ ssh vivek@202.54.1.55

Now login as root user:
$ sudo -i
OR
$ su -i
Edit sshd_config file:
# vim /etc/ssh/sshd_config
OR
# nano /etc/ssh/sshd_config
Find PermitRootLogin and set it as follows:
PermitRootLogin no
Save and close the file. I am going to add a user named vivek to sudoers group on Ubuntu 18.04 server so that we can run sysadmin tasks:
# adduser vivek sudo
Restart/reload the sshd service:
# systemctl reload ssh
You can exit from all session and test it as follows:
$ ssh vivek@202.54.1.55
## become root on server for sysadmin task ##
$ sudo -i

How do I add or replace a passphrase for an existing private key?

To to change your SSH passphrase type the following command:
$ ssh-keygen -p

How do I backup my existing private/public SSH keys

Just copy files to your backup server or external USB pen/hard drive:

How do I protect my ssh keys?

  1. Always use a strong passphrase.
  2. Do not share your private keys anywhere online or store in insecure cloud storage or gitlab/github servers.
  3. Restrict privileges of the account.

Tip: Create and setup an OpenSSH config file to create shortcuts for servers

See how to create and use an OpenSSH ssh_config file for more info.

How do I secure my OpenSSH server?

See “OpenSSH Server Best Security Practices” for more info.

Conclusion

You learned how to create and install ssh keys for SSH key-based authentication for Ubuntu Linux 18.04 LTS server. See OpenSSH server documents here and here for more info.

ADVERTISEMENTS

This brief tutorial shows students and new users how to setup OpenSSH server for key authentication or password-less authentication. This setup allows users of the Ubuntu server to logon via SSH without typing passwords.

This is a much more secure alternative to SSH password authentication. With password authentication, each time a user wants to logon, he/she must always type a password. Another weakness is password can be guessed any anyone.

With key authentication, no password is ever typed. Only client computers with the correct matching key pair to the server are allowed.

To configure SSH with key authentication, follow the steps below:

Step 1: Generate a SSH Key for Each User

To logon via SSH key authentication, you must first generate a key pair. Two keys are created: one public and the other private. The private key must stay on the server and the public key shared with clients securely.

Login via SSH as the user you want to configure, then run the commands below to generate a SSH key pair.

ssh-keygen -t rsa

When prompted, press Enter to accept the default location to store the keys. by default, it’s saved in the user’s home directory in the hidden .ssh folder.

Step 2: Share the Public Key with the Client PC

After creating the key pair above, a public key called id_rsa.pub will be stored in the ~/.ssh/. A folder also called authorized_keys will also be created in that directory. The SSH server looks in the ~/.ssh/authorized_keys for all authorized keys that can logon to the server.

So, run the commands below to move the public key created above into the ~/.ssh/authorized_keys file.

mv ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys

After running the above commands, logon to the client computer. hopefully another Linux machine and run the commands below to copy the public key to the client machine. /starcraft-2-wings-of-liberty-authentication-key-generator.html.

Ssh Generate Key

The key should be copied to the client machine.

Step 3: Logon to SSH without Password

After getting the key to the client computer, logon to the server and open SSH default configuration file by running the commands below

sudo nano /etc/ssh/sshd_config

Then make the highlighted changes below and save the file.

Save the file and restart SSH

sudo systemctl restart ssh

Protect your keys.

On the server, run the commands below to protect the SSH keys.

chmod 600 ~/.ssh/authorized_keys

Now only clients with the matching key pair will be allowed onto the server. To connect, run the commands below replacing server_name with the original servers.

ssh richard@server_name

Will logon without typing a password.

Ubuntu Generate Ssh Key Pair

If you can get the key to a Windows machine, you could use PuTTY to sign on automatically as well.

Enjoy~

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