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Introduction

1. Generate Ssh Keys In Linux
2. Generate Ssh Key In Unix

To set up public-key authentication using SSH on a Linux or macOS computer: Log into the computer you'll use to access the remote host, and then use command-line SSH to. 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.

SSH (Secure Shell) allows secure remote connections between two systems. With this cryptographic protocol, you can manage machines, copy, or move files on a remote server via encrypted channels.

There are two ways to login onto a remote system over SSH – using password authentication or public key authentication (passwordless SSH login).

In this tutorial, you will find out how to set up and enable passwordless SSH login.

• Access to command line/terminal window
• User with sudo or root privileges
• A local server and a remote server
• SSH access to a remote server via command line/terminal window

You may already have an SSH key pair generated on your machine. To see whether you have SSH keys on the system, run the command:

If the output tells you there are no such files, move on to the next step, which shows you how to generate SSH keys.

In case you do have them, you can use the existing keys, back them up and create a new pair or overwrite it.

1. The first thing you need to do is generate an SSH key pair on the machine you are currently working on.

In this example, we generate a 4096-bit key pair. We also add an email address, however this is optional. The command is:

2. Next, type in the location where you want to store the keys or hit Enter to accept the default path.

3. It also asks you to set a passphrase. Although this makes the connection even more secure, it may interrupt when setting up automated processes. Therefore, you can type in a passphrase or just press Enter to skip this step.

4. The output then tells you where it stored the identification and public key and gives you the key fingerprint.

5. Verify you have successfully created the SSH key pair by running the command:

You should see the path of the identification key and the public key, as in the image below:

You can upload the public SSH key to a remote server with the ssh-copy-id command or the cat command. Below you can find both options.

To enable passwordless access, you need to upload a copy of the public key to the remote server.

1. Connect to the remote server and use the ssh-copy-id command:

2. The public key is then automatically copied into the .ssh/authorized_keys file.

Generate Ssh Keys In Linux

Another way to copy the public key to the server is by using the cat command.

1. Start by connecting to the server and creating a .ssh directory on it.

2. Then, type in the password for the remote user.

3. Now you can upload the public key from the local machine to the remote server. The command also specifies that the key will be stored under the name authorized_keys in the newly created .ssh directory:

With the SSH key pair generated and the public key uploaded to the remote server, you should now be able to connect to your dedicated server without providing a password.

Check whether the setup works by running the command:

The system should directly log you in to the remote server, no password required.

Note: Once you verify that you can SHH into the remote serve without a password, consider disabling SSH password authentication altogether. It will add another layer of security and secure your server from brute-force attacks.

Optional: Troubleshooting Remote Server File Permissions

File permissions on the remote server may cause issues with passwordless SSH login. This is a common issue with older versions of SSH.

If you are still prompted for a password after going through all the steps, start by editing file permissions on the remote server.

• Set permissions 700 for the .ssh directory.
• Set permissions 640 for the .ssh/authorized_keys directory.

Edit file permissions with the following command:

Enter your password when prompted. There will be no output if the action was successful. The issue should be resolved now.

If you want to automate updates and other tasks, or seamlessly SSH into a remote server, you should enable passwordless SSH login.

The instructions outlined in this article should have helped you to do so.

For more SSH commands, check out these 19 common SSH commands in Linux with examples.

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Connect to a server by using SSH on Linux or Mac OS X

This article provides steps for connecting to a cloud server froma computer running Linux® or MacOS® X by using Secure Shell (SSH).It also discusses generating an SSH key and adding a public key tothe server.

Introduction

SSH is a protocol through which you can access your cloud server and runshell commands. You can use SSH keys to identify trusted computers withoutthe need for passwords and to interact with your servers.

SSH is encrypted with Secure Sockets Layer (SSL), which makes it difficultfor these communications to be intercepted and read.

Note: Many of the commands in this article must be run on your localcomputer. The default commands listed are for the Linux command line orMacOS X Terminal. To make SSH connections from Windows®, you can use a clientsimilar to the free program, PuTTY.To generate keys, you can use a related program, PuTTYGen.

Log in

Using the Internet Protocol (IP) address and password for your cloud server, log in byrunning the following ssh command with username@ipaddress as the argument:

The system prompts you to enter the password for the account to which you’reconnecting.

Remote host identification

If you rebuilt your cloud server, you might get the following message:

One of the security features of SSH is that when you log in to a cloudserver, the remote host has its own key that identifies it. When you tryto connect, your SSH client checks the server’s key against any keysthat it has saved from previous connections to that IP address. After yourebuild a cloud server, that remote host key changes, so your computerwarns you of possibly suspicious activity.

To ensure the security of your server, you canuse the web console in the Cloud Control Panel to verify your server’s new key.If you’re confident that you aren’t being spoofed, you can skip thatstep and delete the record of the old SSH host key as follows:

On your local computer, edit the SSH known_hosts file and remove anylines that start with your cloud server’s IP address.

Note: Use the editor of your choice, such as nano on Debian or theUbuntu operating systemor vi on RPM or CENTOS servers. For simplicity, this article just uses nano. If you prefer to use vi,substitute vi for nano in the edit commands.For more on using nano, seehttps://support.rackspace.com/how-to/modify-your-hosts-file/.

If you are not using Linux or MacOS X on your local computer, thelocation of the known_hosts file might differ. Refer to your OS forinformation about the file location. PuTTY on Windows gives you theoption to replace the saved host key.

Generate a new SSH key pair

You can secure SSH access to your cloud server against brute forcepassword attacks by using a public-private key pair. A public key is placed onthe server and a matching private key is placed on your local computer. If youconfigure SSH on your server to accept only connections using keys,then no one can log in by using just a password. Connecting clientsare required to use a private key that has a public key registered onthe server. For more on security, reviewLinux server security best practices.

Use the following steps to generate an SSH key pair:

1. Run the following command using your email address as a label.Substitute your email address for your_email@example.com inthe command.

   A message indicates that your public-private RSA key pair isbeing generated.

   At the prompt, press Enter to use the default location or entera file in which to save the key and press Enter.

2. If you want the additional security of a password for the key pair,enter a passphraseand press Enter. If you don’t want to use a passwordwith the key pair, press Enter to continue without setting one.

   Your key pair is generated, and the output looks similar to the following example:

3. Optionally, add your new key to the local ssh-agent file to enableSSH to find your key without the need to specify its location everytime that you connect:

   You can use an SSH configuration shortcut instead of the ssh-agent fileby following the instructions in the Shortcut configuration sectionlater in this article.

Add the public key to your cloud account

To make it easy to add your key to new cloud servers that you create,upload the public key to your cloud account by following these steps:

1. Log in to the Cloud Control Panel.
2. In the top navigation bar, click Select a Product > Rackspace Cloud.
3. Select Servers > SSH Keys.
4. Click Add Public Key.
5. Enter a key name, such as Work Laptop, to remind you which computer this key is for.
6. Select the region for which you want to store the public key. Tostore your key in multiple regions, repeat these steps foreach region. The key must reside in the same region as the server.

7. Paste the contents of the id_rsa.pub file that you created intothe Public Key field. You can get the file contents by eitheropening the file in a text editor or by running the followingcommand:

8. Click Add Public Key.

If you want to add the key manually, instead of by using the Control Panel, reviewLinux server security best practicesand use the following command:

Create a new server by using a stored key

When you create a new cloud server, you can add a stored key to the newserver.

1. On the Create Server page, expand the Advanced Options section.

2. From the SSH Key menu, select your key from the list.

3. If you don’t see a stored key in the list, you can perform one of the following actions:

   • Switch the region for the new server to the region where you have stored the SSH key.
   • Repeat the steps in the preceding section, Add the public key to your cloud account,to add the key to the region in which you want to create the new server.

Add the key to an existing server

You can’t use the Cloud Control Panel to add a public key to anexisting server. Follow these steps to add the key manually:

1. On your cloud server, create a directory named .ssh in the homefolder of the user that you connect to by using SSH.

2. Create or edit the authorized_keys file and add your public key tothe list of authorized keys by using the following command:

   A key is all on one line, so ensure that the key isn’t broken byline breaks. You can have multiple keys in the authorized_keysfile, with one key per line.

3. Set the correct permissions on the key by using the following commands:

4. If you have any issues and need to fix permissions issues, run the following comand:

After you have added the public key to the authorized_keys, you can make an SSHconnection by using your key pair instead of the account password.

Shortcut configuration

Use the following instructions to set up a connection shortcut by creating a~/.ssh/config file on your local computer and adding your server and keydetails to it.

1. Using a text editor, add the following text to the ~/.ssh/config file, changing thevalues to match your server information:

   Each of the following entries describes a feature of the server:

   • Host: A shortcut name that you use to tell SSH to use thisconnection.
   • HostName: The address of the server to which you connect.
   • User: The name of the user account to connect to on theserver.
   • IdentityFile: The location of the private key file (id_rsa).

2. After you set up the config file, connect to the server by usingthe following command with your shortcut name:

Troubleshooting

If you have trouble making a new connection after you restart theserver, use the following steps to help you resolve the issue:

• The best way to troubleshoot SSH or SFTP login issues is to attempt tologin through SSH while logged into the Emergency Console and to watch the log,which typically includes the reason for a failure. If no reason is given,it could be a firewall issue. For RPM servers, run the following command to watch the log:

  For Debian servers, run the following command to watch the log:

• If you get a connection timeout error, check the IP address thatyou used to ensure that it’s correct. You might also check theserver’s iptables to ensure that it isn’t blocking the port used by SSH.
• If you get a connection refused error, you might be trying to useSSH with the wrong port. If you changed your server to listen to aport other than 22, use the -p option with SSH to specifythe port.
• If your login is rejected, then you might have an issuewith your key. Change the sshd configuration to allow passwordconnections by setting PasswordAuthentication to yes. Restartthe server and try again. If you connect after these changes, thenthe issue is with the key and you must verify that the key is in theright place on the server.

• If all else fails, review your changes and restart the SSH daemon onthe server by running the following command:

  If you get a message that the SSH service is unknown, run thecommand with sshd as the service name instead.

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Generate Ssh Key In Unix

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