17.12.2020

Generate New Ssh Keys Linux

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What Are Ssh Keys

I recently read that SSH keys provide a secure way of logging into a Linux and Unix-based server. How do I set up SSH keys on a Linux or Unix based systems? In SSH for Linux/Unix, how do I set up public key authentication?

If you are a new customer, register now for access to product evaluations and purchasing capabilities. Red Hat Enterprise Linux 6 uses SSH Protocol 2 and RSA keys by default (see Section 14.1.3, “Protocol Versions” for more information). Do not generate key pairs as root, as only root would be able to use those keys. Kali Linux SSH Server Kali Linux SSH server is installed by default. You need to just start, stop and restart service to activate it. Remote access Kalli Linux Secure Shell - SSH can be done by client like putty in windows. Jun 13, 2019.

This page explains a public key and shows you how to set up SSH keys on a Linux or Unix-like server. I am assuming that you are using Linux or Unix-like server and client with the following software:

Paste the public key into the.ssh/authorizedkeys file and then press Enter. Note: For most Linux command line interfaces, the Ctrl+Shift+V key combination pastes the contents of the clipboard into the command line window. For the PuTTY command line interface, right-click to paste the contents of the clipboard into the PuTTY command line window. The following command is used to generate these keys in Kali Linux. The first move the original keys form their default directory into a new directory, however, don’t delete them. Mkdir –p /etc/ssh/originalkeys. Mv /etc/ssh/sshhost. /etc/ssh/originalkeys. Generate new keys. Dpkg-reconfigure openssh-server. Start and Restart the Kali Linux SSH Server. Service ssh start. Generating an SSH key pair. An SSH key pair can be generated by running the ssh-keygen command, defaulting to 3072-bit RSA (and SHA256) which the ssh-keygen(1) man page says is 'generally considered sufficient' and should be compatible with virtually all clients and servers: $ ssh-keygen Generating public/private rsa key pair.

What is a public key authentication?

OpenSSH server supports various authentication schema. The two most popular are as follows:

Passwords based authentication
Public key based authentication. It is an alternative security method to using passwords. This method is recommended on a VPS, cloud, dedicated or even home based server.

How to set up SSH keys

Steps to setup secure ssh keys:

Create the ssh key pair using ssh-keygen command.
Copy and install the public ssh key using ssh-copy-id command on a Linux or Unix server.
Add yourself to sudo or wheel group admin account.
Disable the password login for root account.
Test your password less ssh keys login using ssh user@server-name command.

Let us see all steps in details.

How do I set up public key authentication?

You must generate both a public and a private key pair. For example:
Where,

server1.cyberciti.biz – You store your public key on the remote hosts and you have an accounts on this Linux/Unix based server.
client1.cyberciti.biz – Your private key stays on the desktop/laptop/ computer (or local server) you use to connect to server1.cyberciti.biz server. Do not share or give your private file to anyone.

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 server1.cyberciti.biz and client1.cyberciti.biz names with your actual setup. Enough talk, let’s set up public key authentication. Open the Terminal and type following commands if .ssh directory does not exists:

1: Create the key pair

On the computer (such as client1.cyberciti.biz), generate a key pair for the protocol.

Sample outputs:

You need to set the Key Pair location and name. I recommend you use the default location if you do not yet have another key there, for example: $HOME/.ssh/id_rsa. You will be prompted to supply a passphrase (password) for your private key. I suggest that you setup a passphrase when prompted. You should see two new files in $HOME/.ssh/ directory:

$HOME/.ssh/id_rsa– contains your private key.
$HOME/.ssh/id_rsa.pub – contain your public key.

Optional syntax for advance users

The following syntax specifies the 4096 of bits in the RSA key to creation (default 2048):
$ ssh-keygen -t rsa -b 4096 -f ~/.ssh/vps-cloud.web-server.key -C 'My web-server key'
Where,

-t rsa : Specifies the type of key to create. The possible values are “rsa1” for protocol version 1 and “dsa”, “ecdsa”, “ed25519”, or “rsa” for protocol version 2.
-b 4096 : Specifies the number of bits in the key to create
-f ~/.ssh/vps-cloud.web-server.key : Specifies the filename of the key file.
-C 'My web-server key' : Set a new comment.

2: Install the public key in remote server

Use scp or ssh-copy-id command to copy your public key file (e.g., $HOME/.ssh/id_rsa.pub) to your account on the remote server/host (e.g., nixcraft@server1.cyberciti.biz). To do so, enter the following command on your client1.cyberciti.biz:

OR just copy the public key in remote server as authorized_keys in ~/.ssh/ directory:

A note about appending the public key in remote server

On some system ssh-copy-id command may not be installed, so use the following commands (when prompted provide the password for remote user account called vivek) to install and append the public key:

3: Test it (type command on client1.cyberciti.biz)

The syntax is as follows for the ssh command:

Or copy a text file called foo.txt:

You will be prompted for a passphrase. To get rid of passphrase whenever you log in the remote host, try ssh-agent and ssh-add commands.

What are ssh-agent and ssh-add, and how do I use them?

To get rid of a passphrase for the current session, add a passphrase to ssh-agent 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:

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:

Enter your private key passphrase. Now try again to log into user@server1.cyberciti.biz and you will not be prompted for a password:

One can list public key parameters of all identities with the -L option:
ssh-add -L
Deleting all private keys from the ssh-agent can be done with the -D option as follows:
ssh-add -D
When you log out kill the ssh agent, run:
kill $SSH_AGENT_PID
You can also add something like the below to your shell startup to kill ssh-agent at logout:
trap 'kill $SSH_AGENT_PID' 0

4: Disable the password based login on a server

Edit /etc/ssh/sshd_config on server1.cyberciti.biz using a text editor such as nano or vim:

Warning: Make sure you add yourself to sudoers files. Otherwise you will not able to login as root later on. See “How To Add, Delete, and Grant Sudo Privileges to Users on a FreeBSD Server” for more info.

$ sudo vim /etc/ssh/sshd_config
OR directly jump to PermitRootLogin line using a vim text editor:
$ sudo vim +/PermitRootLogin /etc/ssh/sshd_config
Find PermitRootLogin and set it as follows:

Save and close the file. I am going to add a user named vivek to sudoers on Ubuntu Linux:
# adduser vivek
Finally, reload/restart the sshd server, type command as per your Linux/Unix version:

5: How to add or replace a passphrase for an existing private key?

To to change your passphrase type the following command:
ssh-keygen -p

6: How do I backup an existing private/public key?

Just copy files to your backup server or external USB pen/hard drive:

How do I protect my ssh keys?

Always use a strong passphrase.
Do not share your private keys anywhere online or store in insecure cloud storage.
Restrict privileges of the account.

How do I create and setup an OpenSSH config file to create shortcuts for servers I frequently access?

See how to create and use an OpenSSH ssh_config file for more info.

Conclusion

This page explained how to set up ssh keys for authentication purposes. For more info see the following resources:

Man pages – ssh-keygen(1)
OpenSSH project homepage here.

And, there you have it, ssh set up with public key based authentication for Linux or Unix-like systems.

Short Description

Every Amazon EC2 Linux instance launches with a default system user account with administrative access to the instance. If multiple users require access to the instance, it's a security best practice to use separate accounts for each user.

/windows-10-product-key-generator-free-download.html. You can expedite these steps by using cloud-init and user data. For more information, see How can I give a user permissions to connect to my EC2 Linux instance using SSH?

Resolution

Create a key pair for the new user accountHibernate sequence generator non primary key.

Create a key pair, or use an existing one, for the new user.
If you create your own key pair using the command line, follow the recommendations at create-key-pair or New-EC2KeyPair Cmdlet for key type and bit length.
If you create your own key pair using a third-party tool, be sure that your key matches the guidelines at Importing Your Own Public Key to Amazon EC2.

Add a new user to the EC2 Linux instance

1. Connect to your Linux instance using SSH.

2. Use the adduser command to add a new user account to an EC2 instance (replace new_user with the new account name). The following example creates an associated group, home directory, and an entry in the /etc/passwd file of the instance:

Note: If you add the new_user to an Ubuntu instance, include the --disabled-password option to avoid adding a password to the new account:

3. Change the security context to the new_user account so that folders and files you create have the correct permissions:

Note: When you run the sudo su - new_user command, the name at the top of the command shell prompt changes to reflect the new user account context of your shell session.

4. Create a .ssh directory in the new_user home directory:

5. Use the chmod command to change the .ssh directory's permissions to 700. Changing the permissions restricts access so that only the new_user can read, write, or open the .ssh directory.

6. Use the touch command to create the authorized_keys file in the .ssh directory:

7. Use the chmod command to change the .ssh/authorized_keys file permissions to 600. Changing the file permissions restricts read or write access to the new_user.

Retrieve the public key for your key pair

Retrieve the public key for your key pair using the method that applies to your configuration:

Verify your key pair's fingerprint

After you import your own public key or retrieve the public key for your key pair, follow the steps at Verifying Your Key Pair's Fingerprint.

Update and verify the new user account credentials

After you retrieve the public key, use the command shell session that is running under the context of the new user account to confirm that you have permission to add the public key to the .ssh/authorized_keys file for this account:

1. Run the Linux cat command in append mode:

2. Paste the public key into the .ssh/authorized_keys file and then press Enter.

Note: For most Linux command line interfaces, the Ctrl+Shift+V key combination pastes the contents of the clipboard into the command line window. For the PuTTY command line interface, right-click to paste the contents of the clipboard into the PuTTY command line window.

3. Press and hold Ctrl+d to exit cat and return to the command line session prompt.

(Optional) Allow the new user to use sudo

Note: If you don't want to allow the new user to use sudo, proceed to Verify that the new user can use SSH to connect to the EC2 instance.

1. Use the passwd command to create a password for the new user:

Note: You're prompted to reenter the password. Enter the password a second time to confirm it.

2. Add the new user to the correct group.

For Amazon Linux, Amazon Linux 2, RHEL, and CentOS:

Use the usermod command to add the user to the wheel group.

For Ubuntu:

Use the usermod command to add the user to the sudo group.

Verify that the new user can use SSH to connect to the EC2 instance

1. Verify that you can connect to your EC2 instance when using ssh as the new_user by running the following command from a command line prompt on your local computer:

To connect to your EC2 Linux instance using SSH from Windows, follow the steps at Connecting to Your Linux Instance from Windows Using PuTTY.

2. After you connect to your instance as the new_user by using SSH, run the id command from the EC2 instance command line to view the user and group information created for the new_user account:

The id command returns information similar to the following:

3. Distribute the private key file to your new user.

Linux Ssh With Key

Related Information

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