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With a secure shell (SSH) key pair, you can create a Linux virtual machine on Azure that defaults to using SSH keys for authentication, eliminating the need for passwords to sign in. VMs created with the Azure portal, Azure CLI, Resource Manager templates, or other tools can include your SSH public key as part of the deployment, which sets up SSH key authentication for SSH connections.
This article provides detailed background and steps to create and manage an SSH RSA public-private key file pair for SSH client connections. If you want quick commands, see How to create an SSH public-private key pair for Linux VMs in Azure.
Generate Ssh Key Aix
For additional ways to generate and use SSH keys on a Windows computer, see How to use SSH keys with Windows on Azure.
Overview of SSH and keys
- Choose Create key pair. SSH private key file format must be PEM (for example, use ssh-keygen -m PEM to convert the OpenSSH key into the PEM format) Create an RSA key. Amazon EC2 does not accept DSA keys. The supported lengths are 1024, 2048, and 4096. If you connect using SSH while using the EC2 Instance Connect API, the supported lengths.
- 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. Mkdir -p /.ssh. Then restrict the permissions to that directory to just yourself with the command below. Chmod 700 /.ssh. This creates a secure location for you to save your SSH keys for authentication.
SSH is an encrypted connection protocol that allows secure sign-ins over unsecured connections. SSH is the default connection protocol for Linux VMs hosted in Azure. Although SSH itself provides an encrypted connection, using passwords with SSH connections still leaves the VM vulnerable to brute-force attacks or guessing of passwords. A more secure and preferred method of connecting to a VM using SSH is by using a public-private key pair, also known as SSH keys.
The public key is placed on your Linux VM, or any other service that you wish to use with public-key cryptography.
The private key remains on your local system. Protect this private key. Do not share it.
When you use an SSH client to connect to your Linux VM (which has the public key), the remote VM tests the client to make sure it possesses the private key. If the client has the private key, it's granted access to the VM.
Depending on your organization's security policies, you can reuse a single public-private key pair to access multiple Azure VMs and services. You do not need a separate pair of keys for each VM or service you wish to access.
Your public key can be shared with anyone, but only you (or your local security infrastructure) should possess your private key.
All Mac and Linux systems include a command called ssh-keygen that will generate a new key pair. If you're using Windows, you can generate the keys on your server. Just remember to copy your keys to your laptop and delete your private key from the server after you've generated it. To generate an SSH key pair, run the command ssh-keygen. Dec 18, 2019 If the command above prints something like No such file or directory or no matches found it means that you don’t have SSH keys on your client machine and you can proceed with the next step, and generate SSH key pair. If there are existing keys, you can either use those and skip the next step or backup up the old keys and generate new ones. Aug 19, 2019 Learn how to generate SSH keys on CentOS 7. An SSH Key enables a secure passwordless method of logging into a remote server. Learn how to generate SSH keys on CentOS 7. Create a /.ssh directory and authorizedkeys file.
Private key passphrase
– I assume you know how to create an SSH session in MobaXterm, if not – that’s a different set of instructions. Go to “Advanced SSH Settings” 3. Click the box for “Use private key” and choose the file you saved earlier when creating the private key. SSH into your GCE, as the user you created. SU to root as needed. 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 SSH private key should have a very secure passphrase to safeguard it. This passphrase is just to access the private SSH key file and is not the user account password. When you add a passphrase to your SSH key, it encrypts the private key using 128-bit AES, so that the private key is useless without the passphrase to decrypt it. If an attacker stole your private key and that key did not have a passphrase, they would be able to use that private key to sign in to any servers that have the corresponding public key. If a private key is protected by a passphrase, it cannot be used by that attacker, providing an additional layer of security for your infrastructure 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.
SSH keys use and benefits
When you create an Azure VM by specifying the public key, Azure copies the public key (in the .pub format) to the ~/.ssh/authorized_keys folder on the VM. SSH keys in ~/.ssh/authorized_keys are used to challenge the client to match the corresponding private key on an SSH connection. In an Azure Linux VM that uses SSH keys for authentication, Azure configures the SSHD server to not allow password sign-in, only SSH keys. Therefore, by creating an Azure Linux VM with SSH keys, you can help secure the VM deployment and save yourself the typical post-deployment configuration step of disabling passwords in the sshd_config file.
If you do not wish to use SSH keys, you can set up your Linux VM to use password authentication. If your VM is not exposed to the Internet, using passwords may be sufficient. However, you still need to manage your passwords for each Linux VM and maintain healthy password policies and practices, such as minimum password length and regular updates. Using SSH keys reduces the complexity of managing individual credentials across multiple VMs.
Generate keys with ssh-keygen
To create the keys, a preferred command is ssh-keygen, which is available with OpenSSH utilities in the Azure Cloud Shell, a macOS or Linux host, the Windows Subsystem for Linux, and other tools. ssh-keygen asks a series of questions and then writes a private key and a matching public key.
SSH keys are by default kept in the ~/.ssh directory. If you do not have a ~/.ssh directory, the ssh-keygen command creates it for you with the correct permissions.
Basic example
The following ssh-keygen command generates 2048-bit SSH RSA public and private key files by default in the ~/.ssh directory. If an SSH key pair exists in the current location, those files are overwritten.
Detailed example
The following example shows additional command options to create an SSH RSA key pair. If an SSH key pair exists in the current location, those files are overwritten.
Command explained
ssh-keygen = the program used to create the keys
-m PEM = format the key as PEM
-t rsa = type of key to create, in this case in the RSA format
-b 4096 = the number of bits in the key, in this case 4096
-C 'azureuser@myserver' = a comment appended to the end of the public key file to easily identify it. Normally an email address is used as the comment, but use whatever works best for your infrastructure.
-f ~/.ssh/mykeys/myprivatekey = the filename of the private key file, if you choose not to use the default name. A corresponding public key file appended with .pub is generated in the same directory. The directory must exist.
-N mypassphrase = an additional passphrase used to access the private key file.
Example of ssh-keygen
Saved key files
Enter file in which to save the key (/home/azureuser/.ssh/id_rsa): ~/.ssh/id_rsa
The key pair name for this article. Having a key pair named id_rsa is the default; some tools might expect the id_rsa private key file name, so having one is a good idea. The directory ~/.ssh/ is the default location for SSH key pairs and the SSH config file. If not specified with a full path, ssh-keygen creates the keys in the current working directory, not the default ~/.ssh.
List of the ~/.ssh directory
Key passphrase
Git Generate Ssh Key
Enter passphrase (empty for no passphrase):
It is strongly recommended to add a passphrase to your private key. Without a passphrase to protect the key file, anyone with the file can use it to sign in to any server that has the corresponding public key. Adding a passphrase offers more protection in case someone is able to gain access to your private key file, giving you time to change the keys.
Generate keys automatically during deployment
If you use the Azure CLI to create your VM, you can optionally generate SSH public and private key files by running the az vm create command with the --generate-ssh-keys option. The keys are stored in the ~/.ssh directory. Note that this command option does not overwrite keys if they already exist in that location.
Provide SSH public key when deploying a VM
To create a Linux VM that uses SSH keys for authentication, provide your SSH public key when creating the VM using the Azure portal, CLI, Resource Manager templates, or other methods. When using the portal, you enter the public key itself. If you use the Azure CLI to create your VM with an existing public key, specify the value or location of this public key by running the az vm create command with the --ssh-key-value option.
If you're not familiar with the format of an SSH public key, you can see your public key by running cat as follows, replacing ~/.ssh/id_rsa.pub with your own public key file location:
Output is similar to the following (here redacted):
If you copy and paste the contents of the public key file into the Azure portal or a Resource Manager template, make sure you don't copy any additional whitespace or introduce additional line breaks. For example, if you use macOS, you can pipe the public key file (by default, ~/.ssh/id_rsa.pub) to pbcopy to copy the contents (there are other Linux programs that do the same thing, such as xclip).
If you prefer to use a public key that is in a multiline format, you can generate an RFC4716 formatted key in a pem container from the public key you previously created.
To create a RFC4716 formatted key from an existing SSH public key:
SSH to your VM with an SSH client
With the public key deployed on your Azure VM, and the private key on your local system, SSH to your VM using the IP address or DNS name of your VM. Replace azureuser and myvm.westus.cloudapp.azure.com in the following command with the administrator user name and the fully qualified domain name (or IP address):
Powershell Generate Ssh Key
If you provided a passphrase when you created your key pair, enter the passphrase when prompted during the sign-in process. (The server is added to your ~/.ssh/known_hosts folder, and you won't be asked to connect again until 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.
Use ssh-agent to store your private key passphrase
To avoid typing your private key file passphrase with every SSH sign-in, you can use ssh-agent to cache your private key file passphrase. If you are using a Mac, the macOS Keychain securely stores the private key passphrase when you invoke ssh-agent.
Verify and use ssh-agent and ssh-add to inform the SSH system about the key files so that you do not need to use the passphrase interactively.
Now add the private key to ssh-agent using the command ssh-add.
The private key passphrase is now stored in ssh-agent.
Use ssh-copy-id to copy the key to an existing VM
If you have already created a VM, you can install the new SSH public key to your Linux VM with a command similar to the following:
Create and configure an SSH config file
You can create and configure an SSH config file (~/.ssh/config) to speed up log-ins and to optimize your SSH client behavior.
The following example shows a simple configuration that you can use to quickly sign in as a user to a specific VM using the default SSH private key.
Create the file
Generate Ssh Key On Folder Windows 10
Edit the file to add the new SSH configuration
Example configuration
Add configuration settings appropriate for your host VM.
You can add configurations for additional hosts to enable each to use its own dedicated key pair. See SSH config file for more advanced configuration options.
Now that you have an SSH key pair and a configured SSH config file, you are able to sign in to your Linux VM quickly and securely. When you run the following command, SSH locates and loads any settings from the Host myvm block in the SSH config file.
The first time you sign in to a server using an SSH key, the command prompts you for the passphrase for that key file.
Next steps
Next up is to create Azure Linux VMs using the new SSH public key. Azure VMs that are created with an SSH public key as the sign-in are better secured than VMs created with the default sign-in method, passwords.
If you want to use SSH keys in Eclipse, such as if you’re going to connect an Eclipse Git repository with GitHub or BitBucket, you may want to use Eclipse to create and manage the keys for you. It’s pretty easy to do.
Where to store your keys
Generate Ssh Key Github
I recommend storing your keys in a folder named .ssh underneath your home folder. Most programs that use SSH keys expect that, including Eclipse, so unless you’ve got a really good reason to do it differently, go with the standard.
What type of key to use
You’ve got two choices for type of key to use with Eclipse: RSA and DSA. According to this page on StackExchange, you want to use RSA.
The next thing you need to decide is how long your key is. Ideally, we’d use a key length of 2048 or 4096; unfortunately, Eclipse only generates a 1024 bit key. There is a bug report filed against Eclipse to change this, but it’s been open since 2013, so I’m guessing it’s not going to be changed soon. So, I guess I lied — you don’t need to decide how long your key is, because it’s going to be 1024 bits!
Generating the key
Open Eclipse, then from the menu, select Window, and from the Window menu, select Preferences. You’ll get a window that looks like this:
On the left side, expand General (click on the > beside General), then expand Network Connections, and finally select SSH2:
You’ll see here that it defaults to storing the keys in the .ssh folder of your home folder — that’s good, that’s what we want.
Select the Key Management tab:
We want to create an RSA Key, so click the “Generate RSA Key…” button. You’ll get something like this:
So, what’s happened? Eclipse has generated a “key pair”, a pair of matching keys that you can use to authenticate who you are. The idea is that you keep one of the keys secret (the “private” key), and you don’t ever let anyone else ever see that. The other key (the “public” key) you can let anybody see; in fact, they’re going to need to know your public key so that you can authenticate with them. The public key is what’s shown in the “You can paste this public key into the remote authorized_keys file:” box.
The private key is not shown. You will want to save it to your .ssh folder. Before saving it, you need to decide if you want to encrypt the key. If you don’t, anyone who gets access to your .ssh folder can get your private key and pretend they’re you. But, if you do encrypt it, every time you go to use the key, you’re going to have to type in a password. I generally encrypt my private key.
To specify a password to encrypt your private key, enter it into the “Passphrase” field. Type it again into the “Confirm passphrase” field. Be sure to choose a good password! If you don’t type anything into those two fields, your private key will be stored unencrypted. Eclipse will warn you when you try to save your private key:
Generate Ssh Key Windows
In this example, I have typed in a passphrase. When I press the “Save Private Key…” button, I get this dialog box:
You can ignore the “known_hosts” file in there; that’s from something else I’ve done. You probably don’t have it. Anyways, it defaults to saving your private key in a file called “id_rsa”; unless you’ve got a really good reason to change it, just go with the default.
Actually, when I save it, it creates two files: one called “id_rsa” that contains my encrypted private key, and another called “id_rsa.pub” that contains my public key that I can share with anybody.
Done! Now I can share my public key with GitHub or BitBucket, and I can easily authenticate with those systems with Eclipse. Click the “Apply and Close” button, and you’re good to go!