1. The first thing that we need to do is create an SSH key pair to use. Creating this key pair will allow us to add the public key to GitHub. Open a terminal and enter the following command to create the SSH keypair:
2. After entering the command, a prompt appears with a default file path confirmation. Press Enter to accept the default file path.
- I'm having trouble setting up public key authentication for an SSH server on Ubuntu Server 12.04 (A) for authentication from an Ubuntu Server 13.04 (B). What I'm doing now (I'm trying to follow the instructions here): On B: Create a new key with ssh-keygen -C ', using no passphrase, writing to /.ssh/idrsa.
- Supported SSH key formats. Azure currently supports SSH protocol 2 (SSH-2) RSA public-private key pairs with a minimum length of 2048 bits. Other key formats such as ED25519 and ECDSA are not supported. Create an SSH key pair. Use the ssh-keygen command to generate SSH public and private key files. By default, these files are created in the.
3. Next, a password prompt appears. Our goal is convenience, since our public key is being created exclusively for GitHub. Leave the passphrase empty and press Enter.
4. Another prompt appears, this time asking for the passphrase confirmation. Leave this prompt blank as well and press Enter.
Jul 21, 2012 Ubuntu ssh step by step guide. Generate the ssh key pair on your client computer: ssh-keygen. Copy the public key to the server: scp /.ssh/idrsa.pub [email protected]: 3. Connect to the server: ssh [email protected]. Append the public key to authorizedkeys and remove the uploaded copy: cat idrsa.pub /.ssh/authorizedkeys rm idrsa.pub.
5. After passphrase confirmation, our SSH key pair is created and saved within the default file path that we accepted in step 2 of this tutorial. We will need to copy the entire contents of our public key to add to GitHub. To display the contents of the public key, enter the following command into the terminal:
6. The output of the previous command should display the contents of the public key like in the image below.
7. Highlight and copy the entire output of the previous command. Every part must be copied for the SSH key to work when added to GitHub.
8. Now that the public SSH key has been copied to the clipboard, open a web browser and navigate to GitHub, then log in to your account.
9. Click the account icon on the navigation bar on the top-right of the page. Select ‘Settings’ from the dropdown menu that appears.
10. Select ‘SSH and ‘GPG keys’ from the selection pane on the left of the page.
11. Click the green, ‘New SSH key’ button on the top-right of the page.
12. We are taken to the ‘Add New SSH Key’ page. First, enter an identifying title for the SSH key so discerning which computer the matching private key is on is easy.
13. Finally, paste the public SSH key that was copied in step 7 of this tutorial into the ‘Key’ text field.
14. Click the green, ‘Add SSH key’ button to finish the process.
15. Success! The new public SSH key has been added to the GitHub account and can now be used to simplify and secure your work.
I 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?Introduction: 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.
Ubuntu 18.04 Setup SSH Public Key Authentication
The procedure to set up secure ssh keys on Ubuntu 18.04:
- Create the key pair using ssh-keygen command.
- Copy and install the public key using ssh-copy-id command.
- Add yourself to sudo admin account on Ubuntu 18.04 server.
- Disable the password login for root account on Ubuntu 18.04.
Sample set up for SSH Keys on Ubuntu 18.04
Ssh Generate Key
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 [email protected]
## for ED25519 KEY ##
ssh-copy-id -i $HOME/.ssh/id_ed25519.pub [email protected]
## install SSH KEY for root user ##
ssh-copy-id -i $HOME/.ssh/id_ed25519.pub [email protected]
I am going to install ssh key for a user named vivek (type command on your laptop/desktop where you generated RSA/ed25519 keys):$ ssh-copy-id -i ~/.ssh/id_ed25519.pub [email protected]
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 [email protected]
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 [email protected] and you will NOT be prompted for a password:$ ssh [email protected]
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 [email protected]
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 [email protected]
## 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?
- Always use a strong passphrase.
- Do not share your private keys anywhere online or store in insecure cloud storage or gitlab/github servers.
- 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.
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