Generate Ssh Key Putty And Use In Centos

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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, 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.

Apr 21, 2018 NOTE: PuTTY and OpenSSH use different formats for public SSH keys. If the SSH Key you copied starts with “—- BEGIN SSH2 PUBLIC KEY ”, it is in the wrong format. Be sure to follow the instructions carefully. Your key should start with “ssh-rsa AAAA.” Save The Public Key On The Server. Jan 01, 2019  Public key authentication is a feature of PuTTY, in which, we can configure SSH Keys to allow password less logins to Linux machines from our PuTTY terminals. In this article, we are configuring SSH Keys using PuTTYgen and then configure a CentOS 7 machine for password less logins by PuTTY. Dec 18, 2019  Copy the Public Key to CentOS Server # Now that the SSH key pair is generated, the next step is to copy the public key to the server you want to manage. The easiest and the recommended way to copy the public key to the remote server is by using a utility called ssh-copy-id. Generate a private and public key pair Open PuTTYgen.exe, press Generate button, move mouse. Once the keys are generated, type your key passphrase (choose a 'hard to guess' one).

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. 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

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 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 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.

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.

PuTTYgen is a key generator tool for creating pairs of public and private SSH keys. It is one of the components of the open-source networking client PuTTY. Although originally written for Microsoft Windows operating system, it is now officially available for multiple operating systems including macOS, Linux. PuTTYgen.exe is the graphical tool on Windows OS. While on the other side, Linux OS has the only command-line version could be accessible using SSH commands.

  • 1 Download PuTTYgen
    • 1.1 Download PuTTYgen on Windows
    • 1.2 Download PuTTYgen for Mac
    • 1.3 Download PuTTYgen for Ubuntu/Linux
      • 1.3.3 Types of Keys Supported on PuTTYgen

Puttygen aka Putty Key Generator

The key generation utility – PuTTYgen can create various public-key cryptosystems including Rivest–Shamir–Adleman (RSA), Digital Signature Algorithm (DSA), Elliptic Curve Digital Signature Algorithm (ECDSA), and Edwards-curve Digital Signature Algorithm (EdDSA) keys.

The aforementioned public-key cryptosystems principally focus on secure data transmission and digital signatures.

Although PuTTYgen collects keys in its native file format i.e. .ppk files, the keys can easily be converted to any file format. For Windows, the software interface is PuTTYgen.exe, whereas, for Linux OS the command-line adaptation is available using SSH commands.

How to use PuTTYgen?

PuTTYgen is used to generate public or private key pair for creating SSH keys. Below is the complete guidance about how to generate RSA key in the Windows operating system:

  1. Once you install the PuTTY on your machine, you can easily run PuTTYgen. For the same, go to Windows -> Start Menu -> All Programs -> PuTTY -> PuTTYgen.
  2. You will see the PuTTY key generator dialog box on your screen
  3. You will find a “Generate” button in that dialog. Clicking on it will lead to generating the keys for you.
  4. Now you will need to add a unique key passphrase in the Key passphrase and Confirm passphrase field.
  5. Click on the “Save Public Key” and “Save Private Key” buttons to save your public and private keys.
  6. You will see the text starting with ssh-RSA in the Public key for pasting into OpenSSH authorized_keys file field which is located at the top of the window. Copy that entire text to your clipboard by pressing ctrl+c as you will require the key to paste on your clipboard in the public key tool of control panel or directly on the cloud server.

Various Ways to Use RSA Key Pair

Generate ssh key putty and use in centos download

RSA key pair generated through PuTTYgen is used in two various ways defined as below:

  1. To assign while creating a new cloud server
    You can choose the public key from the given list of keys at the time of creating a cloud server. If you don’t find your key in that list, then first add and then assign it.
  2. Assign to an existing cloud server
    At the time of connecting to the cloud server, first of all, you need to tell PuTTY to use it for utilizing your newly created RSA key pair.

PuTTYgen being a component of the terminal emulator PuTTY does not have to be downloaded separately, hence, comes with the PuTTY .msi installation package. You can follow the simple steps to download PuTTYgen software for your system. That is the reason why you don’t need to download PuTTYgen separately. Once you download PuTTY software, you will be able to install and run PuTTYgen easily in no time. Below is the complete instruction about how to download and install PuTTY on Windows.

Apart from that, it is also integrated into third-party programs such as WinSCP installation package. Below you can find a complete PuTTYgen download and installation guide for all operating systems.

Download PuTTYgen on Windows

To download PuTTYgen the primary requisite is to acquire the copy of PuTTY installation package. For the 64-bit operating system, one must install the 64-bit version of PuTTY, i.e. putty-64bit-<version>-installer.msi.Similarly, for the 32-bit operating system, the respective 32-bit version of PuTTY, i.e. putty-<version>-installer.msi needs to be installed.

To get PuTTY, go to PuTTY Installation Download page, whereby the complete installation package will be available with setup instructions, installation guide, and download links to all other components of PuTTY such as putty.exe, pscp.exe, psftp.exe, puttytel.exe, plink.exe, pageant.exe and putty.zip.


Following the successful download of the PuTTY installation package. It is time to install the program. Go to How to install PuTTY on Windows, whereby you will find the step by step guidance for PuTTY installation for Windows operating system.

After successfully downloading and installing PuTTY on your Windows machine, you are just 2-3 clicks away to run PuTTYgen. Follow the below-given step by step guidance to run PuTTYgen:

Run PuTTYgen on Windows

To run PuTTYgen, Go to Windows -> Start Menu -> All Programs -> PuTTY -> PuTTYgen. You will see a window for the PuTTY Key Generator on your screen.

Can't create x-cash wallet because it doesn't generate a key. Voila! Now you can generate public or private key pair using PuTTYgen.

Download PuTTYgen for Mac


Below is the detailed guide to download PuTTYgen on Mac operating system. Mac OS has a built-in command-line SSH client known as Terminal. To utilize it, go to Finder and then opt for Go -> utilities from the top menu. After that find the terminal which supports SSH connections to remote servers.

However, to run PuTTYgen for mac, the first one must have to install PuTTY. There are multiple ways to install PuTTY, which are Homebrew or MacPorts. Both alternatives will also install the command-line of adaptations of PuTTYgen.

Ported PuTTY for Mac

Mac has the port of PuTTY which can be installed in various ways described as below:

  1. Installation using Homebrew:
    First, install the ‘brew command line’ Once installed use the below-given command to install PuTTY:-
    sudo brew install putty
  2. Installation using MacPorts:
    First of all, one must install MacPorts and then use the command-line to install PuTTY. Here is the command to install PuTTY via MacPorts
    sudo port install putty
    Additionally, a user can also add a shortcut to the desktop by writing the following command line
    –cp /opt/local/bin/putty ~/Desktop/PuTTY

However, there is an alternative way to install PuTTY on Mac OS. Cyberduck is a widely used Mac OS SSH Client. Once PuTTY installed on the Mac OS, a user can convert PuTTY derived private key format to OpenSSH.

To convert the private key to standard PEM format, type the following command –

puttygen privatekey.ppk -O private-openssh -o privatekey.pem

You can also read the guide to convert .pem file to .ppk using puttygen.

Download PuTTYgen for Ubuntu/Linux

To download PuTTYgen for Ubuntu (Linux) operating system, a user to first install PuTTY. However, in some Linux distributions, the SSH key generation tool – PuTTYgen needs to be installed independently from the PuTTY client.

For example, Debian Linux requires the below-given code to install PuTTYgen:

sudo apt install putty-tools

Generate Key Pair for Authentication in Linux

To create the key pair for authentication in Linux use the below command:-

puttygen -t rsa -b 2048 -C 'user@host' -o keyfile.ppk

Various Command Line Options of PuTTY in Linux

Below are few important command line options in the Linux operating system for PuTTY:

PuTTYgen [-t keytype [-b bits] [-q] keyfile]
[-C new-comment] [-P]
[-O output-type -p -l -L]
[-o output-file]

Options:

  1. Keyfile – It is the name of the existing key file to read at the time of changing the current key.
  2. –t keytype – The command specifies the type of key to creating. Its acceptable values are RSA and dsa.rsa1.
  3. -b bits – This command specifies a total number of bit in a particular key. 1024 is the perfect size for DSA key, while 2048 or 4096 are the perfect size for RSA keys.
  4. –q – The command suppresses the message about progress at the time of key generation.
  5. -C new-comment – The command will specify the comment to describe the key. It can be used for the new and/or existing key. Key operation is not affected by a comment. However, it is used to recognize the key owner, it’s not reliable completely as any value can be applied to it.
  6. –P – Using the command will update the passphrase of a key. Passphrase helps to encrypt the private key. As passphrase can’t add or update on a command line, it prompts a new passphrase tool to alter it.
  7. –old-passphrase-file – The old password of the key remains in this file. The command is used when the key is protected by a passphrase.
  8. –new-passphrase file – This command prompts the new passphrase of the key. It comes in the action either at the time of generating a new key or while applying –P command to change the passphrase.
  9. -O output-type – This command defines what to give in output. By default, the private key is the output.

Ssh On Centos

Thus, above are the prominent commands of PuTTYgen in Linux operating system. Besides that, there are many other commands available to perform various tasks from the command prompt in Linux at flank speed.

Types of Keys Supported on PuTTYgen

Generate Ssh Key Putty And Use In Centos Command

It is important to know the types of key PuTTYgen supports prior to using it. Below are the key types that it currently supports for SSH-2 and SSH-1 protocol:-

  • SSH-1 protocol:- For SSH-1 only supports one key i.e. Rivest–Shamir–Adleman (RSA)
  • SSH-2 protocol: – SSH-2 supports multiple key types that include – Digital Signature Algorithm (DSA), Elliptic Curve Digital Signature Algorithm (ECDSA) and Ed25519.

Generate Ssh Key Putty And Use In Centos 10

The above description is a detailed brief on downloading and running PuTTYgen on all major operating systems. For further details please check the Download PuTTY page.