Generate An Ssh Key Ubuntu

Ssh Keygen Ubuntu
Generate An Ssh Key Ubuntu Free

SSH stands for “Secure Shell” and is an encrypted protocol used to log in and manage a remote server. SSH also supports various authentication mechanisms. We will show you how to set up SSH key-based authentication on an Ubuntu 18.04 server. Generate the SSH Key on the Client Machine.

Jun 09, 2018 Most Linux and Unix distribution create ssh keys for you during the installation of the OpenSSH server package. But it may be useful to be able re-generate new server keys from time to time. For example, when you duplicate VM (KVM or container) which contains an installed ssh package and you need. Jul 30, 2015 Using key based logins with ssh is generally considered more secure than using plain password logins. This section of the guide will explain the process of generating a set of public/private RSA keys, and using them for logging into your Ubuntu computer(s) via OpenSSH. Generating RSA Keys. The first step involves creating a set of RSA keys for use in authentication. This should be done on the client. To create your public and private SSH keys on the command-line: mkdir /.ssh chmod 700.

How do I regenerate OpenSSH sshd server host keys stored in /etc/ssh/ssh_host_* files? Can I safely regenerate ssh host keys using remote ssh session as my existing ssh connections shouldn’t be interrupted on Debian or Ubuntu Linux? How do I regenerate new ssh server keys? How to regenerate new host keys on a Debian or Ubuntu Linux?
[donotprint][/donotprint]To regenerate keys you need to delete old files and reconfigure openssh-server. It is also safe to run following commands over remote ssh based session. Your Key

Ssh Keygen Ubuntu

existing session shouldn’t be interrupted.

Why regenerate new ssh server keys?

Generate An Ssh Key Ubuntu Free

Most Linux and Unix distribution create ssh keys for you during the installation of the OpenSSH server package. But it may be useful to be able re-generate new server keys from time to time. For example, when you duplicate VM (KVM or container) which contains an installed ssh package and you need to use different keys from cloned KVM VM guest/machine.

Steps to regenerate OpenSSH host keys on Linux

Let us see all steps

Step 1 – Delete old ssh host keys

Login as the root and type the following command to delete files on your SSHD server:
# /bin/rm -v /etc/ssh/ssh_host_*
Sample outputs:

Step 2 – Debian or Ubuntu Linux Regenerate OpenSSH Host Keys

Now create a new set of keys on your SSHD server, enter:
# dpkg-reconfigure openssh-server
Sample output:

You just regenerated new ssh server keys. You need to restart ssh server:
$ sudo systemctl restart ssh
OR
$ /etc/init.d/ssh restart

Step 3 – Update all ssh client(s) known_hosts files

Finally, you need to update ~/.ssh/known_hosts files on client computers, otherwise everyone will see an error message that read as follows:

Either remove host fingerprint or update the file using vi text editor (command must be typed on client machine):
$ ssh-keygen -R remote-server-name-here
Now login using the ssh command:
$ ssh vivek@server1.cyberciti.biz

Conclusion

Quickbooks pro 2013 license key. You just regenerated OpenSSH Host Keys on a Debian or Ubuntu Linux using the dpkg-reconfigure command. For more info see the man page or this wiki page here:
$ man dpkg-reconfigure $ man sshd

Ubuntu 18.04 Setup SSH Public Key Authentication

The procedure to set up secure ssh keys on Ubuntu 18.04:

Create the key pair using ssh-keygen command.
Copy and install the public key using ssh-copy-id command.
Add yourself to sudo admin account on Ubuntu 18.04 server.
Disable the password login for root account on Ubuntu 18.04.

Sample set up for SSH Keys on Ubuntu 18.04

Where,

202.54.1.55 – You store your public key on the remote hosts and you have an accounts on this Ubuntu Linux 18.04 LTS server.
Linux/macbook laptop – Your private key stays on the desktop/laptop/computer (or local server) you use to connect to 202.54.1.55 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 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.

How to create the RSA/ed25519 key pair on your local desktop/laptop

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'

How to install the public key in Ubuntu 18.04 remote server

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

Test it

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

What are ssh-agent and ssh-add, and how do I use them on Ubuntu 18.04?

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

How to disable the password based login on a Ubuntu 18.04 server

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

How do I add or replace a passphrase for an existing private key?

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

How do I backup my existing private/public SSH keys

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 or gitlab/github servers.
Restrict privileges of the account.

Tip: Create and setup an OpenSSH config file to create shortcuts for servers

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

How do I secure my OpenSSH server?

See “OpenSSH Server Best Security Practices” for more info.

Conclusion

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.