With a secure shell (SSH) key pair, you can create virtual machines (VMs) in Azure that use SSH keys for authentication, eliminating the need for passwords to sign in. 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, the Windows Subsystem for Linux, and other tools that support OpenSSH.
VMs created using SSH keys are by default configured with passwords disabled, which greatly increases the difficulty of brute-force guessing attacks.
- Dec 18, 2019 Copy the Public Key to Ubuntu Server # Now that you generated your SSH key pair, the next step is to copy the public key to the server you want to manage. The easiest and the recommended way to copy your public key to the server is to use a utility called ssh-copy-id. On your local machine terminal type: ssh-copy-id [email protected]
- You must have already created an SSL key. See Creating SSH keys. Alternatively, you can use an existing key, if it isn't already being used for a personal account in Bitbucket Server. Using SSH keys to allow access to Bitbucket Server repositories. To get the SSH key to.
Generating Your SSH Public Key Many Git servers authenticate using SSH public keys. In order to provide a public key, each user in your system must generate one if they don’t already have one. This process is similar across all operating systems. A key pair consists of two files, idrsa and idrsa.pub which are private and public keys respectively. The public key resides on the server side, whereas the private key is used when accessing it over SSH protocol. In the following example ssh-keygen command is used to generate the key pair. When generating the key pair, the command prompt.
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
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. The
--generate-ssh-keys option will not overwrite existing key files, instead returning an error. In the following command, replace VMname and RGname with your own values:
Provide an SSH public key when deploying a VM
Generate Ssh Key Ubuntu
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:
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
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 VMname, RGname, and keyFile 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.
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.
Set up your first SSH keys
Use SSH keys for authentication when you are connecting to your server, or even between your servers. They can greatly simplify and increase the security of your login process. When keys are implemented correctly they provide a secure, fast, and easy way of accessing your cloud server.
Follow our guide and learn how to set up your first SSH keys for authentication using OpenSSH or PuTTYTray.
Preparing your server
To add an SSH key pair, first, create a hidden folder to your user account home directory on your cloud server with the following command.
Then restrict the permissions to that directory to just yourself with the command below.
This creates a secure location for you to save your SSH keys for authentication. However, note that since the keys are stored in your user home directory, every user that wishes to connect using SSH keys for authentication has to repeat these steps on their own profile.
Using OpenSSH to generate a key pair
Now continue on your own computer if you are using Linux or any other OS that has OpenSSH. PuTTY users should skip to the next section.
1. Generate a new key pair in a terminal with the next command
The key generator will ask for location and file name to which the key is saved to. Enter a new name or use the default by pressing enter.
2. (Optional) Create a passphrase for the key when prompted
This is a simple password that will protect your private key should someone be able to get their hands on it. Enter the password you wish or continue without a password. Press enter twice. Note that some automation tools might not be able to unlock passphrase-protected private keys.
3. Copy the public half of the key pair to your cloud server using the following command
Replace the user and server with your username and the server address you wish to use the key authentication on.
This also assumes you saved the key pair using the default file name and location. If not, just replace the key path ~/.ssh/id_rsa.pub above with your own key name.
Enter your user account password for that SSH server when prompted.
You can now authenticate to your server with the key pair, but at the moment you would need to enter the passphrase every time you connect.
4. (Optional) Set up SSH Agent to store the keys to avoid having to re-enter passphrase at every login
Enter the following commands to start the agent and add the private SSH key.
Type in your key’s current passphrase when asked. If you saved the private key somewhere other than the default location and name, you’ll have to specify it when adding the key.
Afterwards, you can connect to your cloud server using the keys for authentication, and only having to unlock the key by repeating the last 2 steps once after every computer restart.
Using PuTTYTray to generate a key pair
If you are running Windows and PuTTYTray for SSH, you can use the built-in key generator from PuTTY to create a new key pair.
1. Click the Keygen button at the bottom of the PuTTY Configuration window to get started.
Then in the Key Generator window, check that the Type of key to generate at the bottom is set to SSH-2 RSA. The older SSH-1 was the first version on the standard but is now generally considered obsolete. Most modern servers and clients support SSH-2.
2. Click the Generate button to begin.
Ssh Generate Keys
3. Keep moving your mouse over the blank area in any manner to help generate randomness for a few moments until the progress is complete.
How To Generate Ssh Keys
With the keys finished, PuTTY will show the relative information about the pair along with the public key for easier copying.
4. (Optional) Enter a key passphrase in the 2 empty fields for the added security before continuing. The passphrase will protect your key from unauthorized use should someone be able to copy it. However, some automation tools might not be able to unlock passphrase-protected private keys.
5. Click the Save private key button and store it somewhere safe. Generally anywhere in your user directory is fine as long as your PC is password protected. Before closing the keygen, you may want to copy the public key to your clipboard, but you can always get it later as well.
Now that you have a new key saved on your computer, you’ll need to import it into the PuTTY key agent.
6. Click the Agent button to open the key manager in the PuTTY Configuration window.
7. Click Add Key button in the Key List, then browse to the location you saved the private key, select it and click Open.
Enter your key passphrase if asked.
This will import the key to your PuTTY client, but you still need to copy the public key over to your server.
8. Open an SSH connection to your cloud server and go to the SSH key directory.
9. Open or create the default file OpenSSH looks for public keys called authorized_keys.
10. Paste the public key into the file by simply right-clicking the SSH client window. Make sure the key goes on a single line for OpenSSH to be able to read it.
When you’ve copied the public key over to the authorized keys list, save the file and exit the editor. You can now test the public key authentication by logging in to your server again. You should not get asked for your password, but instead logged straight in with the key. If it’s not working, check that your private key is unlocked at your SSH Agent and try again.
Turn off password authentication
With SSH key authentication configured and tested, you can disable password authentication for SSH all together to prevent brute-forcing. When logged in to your cloud server.
1. Open the SSH configuration file with the following command.
2. Set the password authentication to no to disable clear text passwords.
3. Check that public key authentication is enabled, just to be safe and not get locked out from your server. If you do find yourself unable to log in with SSH, you can always use the Web terminal at your UpCloud control panel.
Then save and exit the editor.
4. Restart the SSH service to apply the changes by using the command below.
With that done your cloud server is now another step along towards security. Malicious attempts to connect to your server will results in authentication rejection, as plain passwords are not allowed, and brute-forcing an RSA key is practically impossible.
Remember to always keep your private keys safe. You can use the same key from multiple computers if you wish, or generate new ones on each client connecting to your cloud server for added security. Each user should generate their own key pair and passphrase for secure access control. With proper management, even in case one of the private keys gets compromised you won’t have to replace them all.