Ssh Private Key Example

Private keys allow the users to login to SSH without a password. This is considered a safe practice in some cases while also discards the need to remember multiple passwords.

Note that if the SSH private key isn't stored in the file or in the path that the ssh utility expects (for example, the ssh utility might expect the private key to be stored in /.ssh/idrsa), you must explicitly specify the private key filename and location in one of two ways. Generate ssh key without any arguments. You can execute ssh-keygen without any arguments. Adding an Arbitrary Key. To add an arbitrary private key, give the path of the key file as an argument to ssh-add. For example, ssh-add /.ssh/tatu-aws-key. Would add the file /.ssh/tatu-aws-key. Keys with Passphrases. If the key being added has a passphrase, ssh-add will run the ssh-askpass program to. Say, for example, you need to add a certificate for authentication in GitHub (or any other online service that requires SSH authentication). SSH will compare the public and private keys.

In this tutorial, we would learn how to generate our own SSH Key Pair on our local machine and then configure our Server to use the same for authentication when trying to connect over SSH.

Is there some other way to authenticate with only a username or hostname and private key using SSH.NET lib? C#.net ssh private-key ssh.net. Improve this question. Follow edited Nov 21 '18 at 7:15. 145k 38 38 gold badges 328 328 silver badges 688 688 bronze badges.

Steps to Login to SSH Without A Password

Let’s go over the process step-by-step to login to SSH without a password. If you’re new, you can start by reading more about how to connect to a remote host using SSH. If you’re ready, let’s get started.

Step 1: Generate SSH Key Pair

On our local machine, we can generate a SSH Key Pair with the following command :

On execution, we are prompted to specify a file in which to save the private key, the default being /home/user/.ssh/id_rsa ; here id_rsa is the name of our Private Key file. You can always specify a different path and name for the Private Key file. For our demonstration, we shall use the default configuration.

Step 2: Provide A Passphrase (Optional)

Next, we are presented with a prompt that asks us for a passphrase that can be used to protect the SSH Private Key from unauthorized access.

However, this field is optional and if left empty, it stores the Private Key file without any protection. In our example, we would leave this field empty. After this, we would have successfully generated our Key Pair. We are also presented with a ‘fingerprint’ and ‘visual fingerprint’ of our key which we need not save.

Step 3: Configure the Server To Use Our Private Key

At this point, we should have the following two files under /home/user/.ssh :

  • id_rsa : Our SSH Private Key
  • id_rsa.pub : Our SSH Public Key
Private

Take note of the permissions of the private key ( id_rsa ). SSH Private Key files should ALWAYS HAVE 600 PERMISSIONS! If not, change its permission to the said value using the chmod command:

Ssh Using Private Key Example

Next, we need to configure our Server to use our private key for login. Now this can be done manually by logging into the Server and configuring stuff manually but there’s a tool ssh-copy-id which does all the hard work for us !

Hence, to configure our Server to use our private key, simply run :

Here,

  • USER is the username we want to login as onto the server
  • IP is the IP address of our Server

And with that, we can now simply SSH into our Server with :

If you had previously specified a passphrase, you will get a prompt asking for the same :

Note that if you are not using the default path and file names then you need to specify the private key file using the -i flag as follows :

Ssh Private Key Example Excel

Thus we successfully SSH’d into our machine using our PRIVATE KEY !

Conclusion

And with that, we were able to login to SSH without a password on our Linux machine. It’s an easy and more secure way of logging in as it locks you to log in from specific IP addresses. If you’re interested in learning more on Linux topics, continue to follow LinuxForDevices.

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With a secure shell (SSH) key pair, you can create virtual machines (VMs) in Azure that use SSH keys for authentication. This article shows you how to quickly generate and use an SSH public-private key file pair for Linux VMs. You can complete these steps with the Azure Cloud Shell, a macOS or Linux host.

Note

VMs created using SSH keys are by default configured with passwords disabled, which greatly increases the difficulty of brute-force guessing attacks.

For more background and examples, see Detailed steps to create SSH key pairs.

For additional ways to generate and use SSH keys on a Windows computer, see How to use SSH keys with Windows on Azure.

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 ~/.ssh directory. You can specify a different location, and an optional password (passphrase) to access the private key file. If an SSH key pair with the same name exists in the given location, those files are overwritten.

The following command creates an SSH key pair using RSA encryption and a bit length of 4096:

If you use the Azure CLI to create your VM with the az vm create command, you can optionally generate SSH public and private key files using the --generate-ssh-keys option. The key files are stored in the ~/.ssh directory unless specified otherwise with the --ssh-dest-key-path option. If an ssh key pair already exists and the --generate-ssh-keys option is used, a new key pair will not be generated but instead the existing key pair will be used. In the following command, replace VMname and RGname with your own values:

Provide an SSH public key when deploying a VM

Terraform Ssh Private Key Example

To create a Linux VM that uses SSH keys for authentication, specify your SSH public key when creating the VM using the Azure portal, Azure CLI, Azure Resource Manager templates, or other methods:

If you're not familiar with the format of an SSH public key, you can display your public key with the following cat command, replacing ~/.ssh/id_rsa.pub with the path and filename of your own public key file if needed:

Ssh

A typical public key value looks like this example:

If you copy and paste the contents of the public key file to use in the Azure portal or a Resource Manager template, make sure you don't copy any trailing whitespace. To copy a public key in macOS, you can pipe the public key file to pbcopy. Similarly in Linux, you can pipe the public key file to programs such as xclip.

The public key that you place on your Linux VM in Azure is by default stored in ~/.ssh/id_rsa.pub, unless you specified a different location when you created the key pair. To use the Azure CLI 2.0 to create your VM with an existing public key, specify the value and optionally the location of this public key using the az vm create command with the --ssh-key-values option. In the following command, replace myVM, myResourceGroup, UbuntuLTS, azureuser, and mysshkey.pub with your own values:

If you want to use multiple SSH keys with your VM, you can enter them in a space-separated list, like this --ssh-key-values sshkey-desktop.pub sshkey-laptop.pub.

SSH into your VM

With the public key deployed on your Azure VM, and the private key on your local system, SSH into your VM using the IP address or DNS name of your VM. In the following command, replace azureuser and myvm.westus.cloudapp.azure.com with the administrator user name and the fully qualified domain name (or IP address):

If you specified a passphrase when you created your key pair, enter that passphrase when prompted during the login process. The VM is added to your ~/.ssh/known_hosts file, and you won't be asked to connect again until either the public key on your Azure VM changes or the server name is removed from ~/.ssh/known_hosts.

If the VM is using the just-in-time access policy, you need to request access before you can connect to the VM. For more information about the just-in-time policy, see Manage virtual machine access using the just in time policy.

Next steps

  • For more information on working with SSH key pairs, see Detailed steps to create and manage SSH key pairs.

  • If you have difficulties with SSH connections to Azure VMs, see Troubleshoot SSH connections to an Azure Linux VM.