Jul 29, 2019 This process creates two keys. One is a public key, which you can hand out to anyone – in this case, you’ll save it to the server. The other one is a private key, which you will need to keep secure. The secure private key ensures that you are the only person who can encrypt the data that is decrypted by the public key. In case you travel and can’t carry your laptop with you, just keep your private key on a USB stick and attach it to your physical keychain. Your server will be much safer this way. Generate Public/Private SSH Key Pair. Open Command Prompt from the Start Menu and type. Feb 15, 2012 Ubuntu Linux - How to generate private and public key using OpenSSL. Configure SSH Server for Private Key Authentication in Ubuntu -Part1. Symmetric Key and Public Key Encryption. Use the ssh-keygen command to generate SSH public and private key files. By default, these files are created in the /.ssh directory. 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.
The procedure to set up secure ssh keys on Ubuntu 18.04:
Where,
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.
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'
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 user@202.54.1.55
## for ED25519 KEY ##
ssh-copy-id -i $HOME/.ssh/id_ed25519.pub user@202.54.1.55
## install SSH KEY for root user ##
ssh-copy-id -i $HOME/.ssh/id_ed25519.pub root@202.54.1.55
I am going to install ssh key for a user named vivek (type command on your laptop/desktop where you generated RSA/ed25519 keys):$ ssh-copy-id -i ~/.ssh/id_ed25519.pub vivek@202.54.1.55
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 vivek@202.54.1.55
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 vivek@202.54.1.55 and you will NOT be prompted for a password:$ ssh vivek@202.54.1.55
Login to your server, type:## client commands ##
$ eval $(ssh-agent)
$ ssh-add
$ ssh vivek@202.54.1.55
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 vivek@202.54.1.55
## become root on server for sysadmin task ##
$ sudo -i
To to change your SSH passphrase type the following command:$ ssh-keygen -p
Just copy files to your backup server or external USB pen/hard drive:
See how to create and use an OpenSSH ssh_config file for more info.
See “OpenSSH Server Best Security Practices” for more info.
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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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.
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.
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.
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:
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.
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.